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manet-thesis-99mar - 1998:362 MASTER'S THESIS Routing. Click to edit the document details. Unformatted text preview: 1998:362 MASTER'S THESIS Routing Protocols in Wireless Ad-hoc Networks A Simulation Study Tony Larsson, Nicklas Hedman Civilingenjorsprogrammet 1998:362 • ISSN: 1402-1617 • ISRN: LTU-EX--98/362--SE Master’s thesis in Computer Science and Engineering Routing Protocols in Wireless Ad-hoc Networks A Simulation Study Stockholm, 1998 Tony Larsson and Nicklas Hedman Lulea University of Technology Supervisor: Per Johansson Switchlab Ericsson Telecom AB Examiner: Mikael Degermark Department of Computer Science and Electrical Engineering Division of Computer Communications, Lulea University of Technology Abstract Ad-hoc networking is a concept in computer communications, which means that users wanting to communicate with each other form a temporary network, without any form of hachiko book report, centralized administration. Each node participating in the network acts both as host and a router and must therefore be willing to forward packets for other nodes. For this purpose, a routing protocol is needed. Greener Place? An ad-hoc network has certain characteristics, which imposes new demands on the routing protocol. Hachiko Book Report? The most important characteristic is the dynamic topology, which is a consequence of andreas dahmen dissertation, node mobility. Nodes can change position quite frequently, which means that we need a routing protocol that quickly adapts to topology changes. The nodes in an ad-hoc network can consist of laptops and personal digital assistants and book report are often very limited in resources such as CPU capacity, storage capacity, battery power and bandwidth.
This means that the andreas dissertation routing protocol should try to minimize control traffic, such as periodic update messages. Instead the waits routing protocol should be reactive, thus only calculate routes upon receiving a specific request. The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networks that is frederick jackson thesis the american frontier working on routing specifications for ad-hoc networks. This master thesis evaluates some of the hachiko waits report protocols put forth by on flower the working group. This evaluation is done by means of simulation using Network simulator 2 from Berkeley.
The simulations have shown that there certainly is a need for a special ad-hoc routing protocol when mobility increases. More conventional routing protocols like DSDV have a dramatic decrease in performance when mobility is hachiko book report high. Two of the proposed protocols are DSR and AODV. They perform very well when mobility is high. Greener Place Essay? However, we have found that a routing protocol that entirely depends on messages at the IP-level will not perform well. Some sort of hachiko report, support from the lower layer, for instance link failure detection or neighbor discovery is necessary for high performance. The size of the network and the offered traffic load affects protocols based on source routing, like DSR, to some extent. A large network with many mobile nodes and high offered load will increase the overhead for DSR quite drastically.
In these situations, a hop-by-hop based routing protocol like AODV is more desirable. Preface This report is the jackson the american frontier result of our master thesis project carried out at Ericsson Telecom, Switchlab in waits Stockholm. This master thesis is also the last part of our Master of Science degree at Lulea University of graduate questions, Technology. Switchlab is an applied research organization within Ericsson, working on network studies and technologies for products in the foreseeable future. This master thesis project has been a cooperation between Switchlab in Stockholm and book Ericsson Mobile Data Design (ERV) in Gothenburg.
Our master thesis consisted of graduate questions nursing, conducting a simulation study of proposed routing protocols in hachiko waits ad-hoc networks. The thesis work done at ERV implemented one of the proposed routing protocols and tested it in a simple scenario. This has made it possible to share thoughts and film essay ideas with each other. We would like to thank the following persons: Per Johansson for being our supervisor at Switchlab, Bartosz Mielczarek for contribution of the realistic scenarios and Mikael Degermark for being our Examiner at waits book report, Lulea University of turner thesis about, Technology. Hachiko? Also thanks to Johan Kopman and Jerry Svedlund in Gothenburg for discussions and comments regarding AODV. Place Essay? Finally, we would also like to thank Mats Westin and Henrik Eriksson for giving us feedback on this report. Table of Contents 1 INTRODUCTION . 9 1.1 1.2 1.3 1.4 1.5 1.6 2 BACKGROUND . Waits? 9 PROBLEM DESCRIPTION . 9 RELATED WORK . 10 PROJECT ORGANIZATION . 10 DISPOSITION . 11 ABBREVIATIONS . 11 GENERAL CONCEPTS.
12 2.1 WIRELESS AD-HOC NETWORKS . Good Essays Career Goals? 12 2.1.1 General. Hachiko Book? 12 2.1.2 Usage. 13 2.1.3 Characteristics . Greener Place? 13 2.2 ROUTING . Waits Book? 14 2.2.1 Conventional protocols . Essay? 14 2.2.2 Link State. 14 2.2.3 Distance Vector . 14 2.2.4 Source Routing . 14 2.2.5 Flooding . 15 2.2.6 Classification. 15 3 AD-HOC ROUTING PROTOCOLS. Hachiko Waits Book? 16 3.1 DESIRABLE PROPERTIES . 16 3.2 MANET. Graduate Essay? 17 3.3 DESTINATION SEQUENCED DISTANCE VECTOR - DSDV . 17 3.3.1 Description . 17 3.3.2 Properties . 17 3.4 AD-HOC ON DEMAND DISTANCE VECTOR - AODV . Hachiko Report? 18 3.4.1 Description . 18 3.4.2 Properties . Essay On Flower? 19 3.5 DYNAMIC SOURCE ROUTING - DSR.
20 3.5.1 Description . 20 3.5.2 Properties . 20 3.6 ZONE ROUTING PROTOCOL - ZRP . 21 3.6.1 Description . Report? 21 3.6.2 Properties . 22 3.7 TEMPORALLY-ORDERED ROUTING ALGORITHM - TORA . 22 3.7.1 Description . Frederick Jackson Turner The American Frontier? 22 3.7.2 Properties . 23 3.8 INTERNET MANET ENCAPSULATION PROTOCOL - IMEP. 24 3.8.1 Description . 24 3.8.2 Properties . 24 3.9 CLUSTER BASED ROUTING PROTOCOL - CBRP. Report? 24 3.9.1 Description . 24 3.9.2 Properties . 26 3.10 COMPARISON. 26 4 SIMULATION ENVIRONMENT . 28 4.1 NETWORK SIMULATOR. 28 4.2 MOBILITY EXTENSION . 29 4.2.1 Shared media. Graduate Questions Nursing? 30 4.2.2 Mobile node. 30 4.3 SIMULATION OVERVIEW . Waits Book? 31 4.4 MODIFICATIONS . 32 4.4.1 AODV . 32 4.4.2 DSR. Good About Career Goals? 33 4.4.3 DSDV. 34 4.4.4 Flooding . 34 4.4.5 The simulator.
34 5 SIMULATION STUDY . Hachiko Waits Book Report? 35 5.1 MEASUREMENTS . Compare Film? 35 5.1.1 Quantitative metrics . 35 5.1.2 Parameters . 35 5.1.3 Mobility . 35 5.2 SIMULATION SETUP . 38 5.3 MOBILITY SIMULATIONS . 39 5.3.1 Setup . Report? 39 5.3.2 Fraction of received packets. 40 5.3.3 End-to-end delay . Graduate Essay Questions Nursing? 41 5.3.4 End-to-end throughput . 42 5.3.5 Overhead . 43 5.3.6 Optimal path. Book Report? 44 5.3.7 Summary mobility simulations. Dissertation? 46 5.4 OFFERED LOAD SIMULATIONS . 46 5.4.1 Setup . 46 5.4.2 Fraction of received packets. 47 5.4.3 End-to-end delay . Report? 48 5.4.4 End-to-end throughput . 49 5.4.5 Overhead . Jackson Thesis About? 49 5.4.6 Optimal path.
51 5.4.7 Summary offered load simulations . 51 5.5 NETWORK SIZE SIMULATIONS. 52 5.6 REALISTIC SCENARIOS . 52 5.6.1 Setup . 52 5.6.2 Conference. 53 5.6.3 Event coverage . 55 5.6.4 Disaster area . 57 5.6.5 Summary realistic scenarios. 60 5.7 OBSERVATIONS . Book Report? 60 5.7.1 Ability to find routes . 60 5.7.2 Temporary backward routes. 61 5.7.3 Buffers . 62 5.8 DISCUSSION. 62 5.9 CLASSIFICATION. 62 5.9.1 Mobile networks . Questions? 63 5.9.2 Size of networks . 63 5.9.3 Network scenarios . Hachiko Book? 64 5.10 IMPROVEMENTS . 64 6 IMPLEMENTATION STUDY . 65 DESIGN. Greener Essay? 65 6.1.1 Main . 65 6.1.2 Event queue . 66 6.1.3 Route table. Waits? 66 6.1.4 Neighbors / senders . 66 6.1.5 Request buffer.
66 6.1.6 Message . 66 6.2 SETUP . The American? 66 6.3 TESTING . 67 6.3.1 Correctness. Book Report? 67 6.3.2 Performance . 67 6.4 6.5 6.6 7 CONCLUSIONS. 69 7.1 7.2 8 PROBLEMS / LIMITATIONS . 67 IMPROVEMENTS . 68 IMPLEMENTATION CONCLUSIONS . 68 RESULTS. 69 FURTHER STUDIES . 69 REFERENCES . 71 APPENDIX A - TERMINOLOGY. 73 A.1 A.2 GENERAL TERMS . 73 AD-HOC RELATED TERMS . 74 APPENDIX B - AODV IMPLEMENTATION FOR NS. 75 B.1 MESSAGE FORMATS. 75 B.1.1 Route Request – RREQ. 75 B.1.2 Route Reply - RREP. 76 B.1.3 Hello . Greener? 76 B.1.4 Link failure . 76 B.2 DESIGN . 77 B.3 IMPORTANT ROUTINES.
78 B.3.1 Sending RREQ. 78 B.3.2 Receiving RREQ . 78 B.3.3 Forwarding RREQ. 79 B.3.4 Forwarding RREP . 79 B.3.5 Receiving RREP . 79 B.3.6 Hello handling . 80 B.3.7 Forwarding packets. 80 B.3.8 Sending Triggered RREP . 80 B.3.9 Receiving Triggered RREP. 80 APPENDIX C - SIMULATOR SCREENSHOTS . 81 C.1 C.2 NETWORK ANIMATOR . 81 AD-HOCKEY . 82 List of Figures Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: Figure 7: Figure 8: Figure 9: Figure 10: Figure 11: Figure 12: Figure 13: Figure 14: Figure 15: Figure 16: Figure 17: Figure 18: Figure 19: Figure 20: Figure 21: Figure 22: Figure 23: Figure 24: Figure 25: Figure 26: Figure 27: Figure 28: Figure 29: Figure 30: Figure 31: Figure 32: Figure 33: Figure 34: Figure 35: Example of waits book, a simple ad-hoc network with three participating nodes. . 12 Block diagram of a mobile node acting both as hosts and as router. . 13 Network using ZRP. The dashed squares show the routing zones for nodes S and D. Dahmen? 22 Directed acyclic graph rooted at destination. 23 IMEP in the protocol stack. Hachiko Waits? . 24 Bi-directional linked clusters. Greener? 25 Network simulator 2. . 28 Shared media model. . 30 A mobile node. . Hachiko? 31 Simulation overview. 32 Example of mobility. Essay Questions? . 37 Relation between the number of link changes and hachiko waits mobility. Place Essay? . 37 Mobility simulations - fraction of received packets. . 40 Mobility simulations - delay. 41 Mobility simulations - throughput. . 42 Mobility simulations - overhead.
43 Mobility simulations - optimal path difference. . 45 Offered load simulations - fraction of report, received packets. Andreas Dissertation? . 47 Offered load simulations - average delay. . 48 Offered load simulations - average throughput. . 49 Offered load simulations - overhead. 50 Offered load simulations – optimal path. Book Report? 51 Conference scenario. Essay Nursing? . 54 Event coverage scenario. . 56 Disaster area scenario. . 58 Simple example scenario. . 60 Overview of AODV daemon. Waits Book? . 65 Different router identification approaches. From left to right: 3a, 3b, 3c. 70 Route request format. . 75 Route reply format. 76 AODV design of implementation for simulator. . 77 Screenshot – Network animator. 81 Screenshot – Ad-hockey – Conference scenario. Essay On Flower? . 82 Screenshot – Ad-hockey – Event coverage scenario. . Book? 83 Screenshot – Ad-hockey – Disaster area. . 83 List of essay, Tables Table 1: Table 2: Table 3: Table 4: Table 5: Table 6: Table 7: Table 8: Table 9: Table 10: Table 11: Table 12: Table 13: Table 14: Table 15: Table 16: Table 17: Table 18: Table 19: Table 20: Table 21: Neighbor table. . 25 Comparison between ad-hoc routing protocols. . 27 Constants used in the AODV implementation. 33 Constants used in the DSR implementation. . Book Report? 33 Constants used in the DSDV implementation. Andreas? . 34 Mobility variables. 36 Parameters used during mobility simulations. 39 Optimal path difference for hachiko book report, all protocols. 45 Parameters used during offered load simulations. . 47 Parameters used during realistic simulations.
53 Parameters used during conference scenario. . 53 Conference simulation results. . Place Essay? 54 Packet drops in conference scenario. 55 Parameters used during event coverage scenario. . 55 Event coverage simulation results. . 57 Packet drops in event coverage scenario. . 57 Parameters used during disaster area scenario. 57 Disaster area simulation results. . 59 Packet drops in hachiko waits disaster area. 59 Routing tables for AODV after a route discovery process. . 60 Routing caches for DSR, after a route discovery process. 61 1 Introduction 1.1 Background Wireless communication between mobile users is becoming more popular than ever before. This due to recent technological advances in laptop computers and wireless data communication devices, such as wireless modems and wireless LANs. This has lead to lower prices and higher data rates, which are the about two main reasons why mobile computing continues to enjoy rapid growth.
There are two distinct approaches for enabling wireless communication between two hosts. The first approach is to let the existing cellular network infrastructure carry data as well as voice. The major problems include the problem of handoff, which tries to handle the report situation when a connection should be smoothly handed over from one base station to another base station without noticeable delay or packet loss. Another problem is that networks based on the cellular infrastructure are limited to places where there exists such a cellular network infrastructure. The second approach is to form an ad-hoc network among all users wanting to communicate with each other. This means that all users participating in the ad-hoc network must be willing to essay, forward data packets to make sure that the book packets are delivered from source to destination. This form of networking is good about career limited in range by hachiko book the individual nodes transmission ranges and is typically smaller compared to thesis the american, the range of cellular systems. This does not mean that the cellular approach is better than the ad-hoc approach. Ad-hoc networks have several advantages compared to traditional cellular systems. These advantages include: N N N On demand setup Fault tolerance Unconstrained connectivity Ad-hoc networks do not rely on any pre-established infrastructure and can therefore be deployed in places with no infrastructure. This is useful in disaster recovery situations and places with non-existing or damaged communication infrastructure where rapid deployment of waits report, a communication network is needed.
Adhoc networks can also be useful on conferences where people participating in the conference can form a temporary network without engaging the services of any pre-existing network. Because nodes are forwarding packets for each other, some sort of routing protocol is necessary to make the routing decisions. Greener Place Essay? Currently there does not exist any standard for a routing protocol for ad-hoc networks, instead this is work in progress. Waits Report? Many problems remain to be solved before any standard can be determined. This thesis looks at some of these problems and tries to evaluate some of the currently proposed protocols. 1.2 Problem description The objective for this master thesis was to evaluate proposed routing protocols for wireless ad-hoc networks based on performance.
This evaluation should be done theoretically and through simulation. It was also desirable to compare the results with the results for routing protocols in a traditional wired network. Nursing? At the beginning of this master thesis, no implementation of the protocols had been released, so the hachiko book report first main task was to implement some of the protocols. The thesis also included the goal to generate a simulation environment that could be used as a platform for further studies within the area of ad-hoc networks. This simulation environment should if possible, be based on Network simulator 2 from Berkeley. 9 The goal of this master thesis was to: N N N N N N Get a general understanding of ad-hoc networks. Generate a simulation environment that could be used for further studies. Implement some of the proposed routing protocols for wireless ad-hoc networks.
Analyze the protocols theoretically and through simulation. Produce a classification of the protocols with respect to applicability in combinations of small/large networks, and mobile/semi-mobile nodes. Recommend protocols for specific network scenarios. 1.3 Related work Many routing protocols have been proposed , but few comparisons between the different protocols have been made. Of the work that has been done in essay on flower garden this field, only the work done by the Monarch1 project at Carnegie Mellon University (CMU) has compared some of the different proposed routing protocols and evaluated them based on the same quantitative metrics. The result was presented in book report the article “A performance comparison of multi-hop ad hoc wireless network routing protocols”  that was released in dahmen dissertation the beginning of October 1998. There exist some other simulation results  that have been done on individual protocols. These simulations have however not used the same metrics and are therefore not comparable with each other. In parallel with our master thesis, a master thesis project in Gothenburg  implemented the AODV  protocol and hachiko report tested it in a environment that consisted of 5 computers with wireless interfaces. The cooperation between our projects and nursing their project made it possible to report, share thoughts and ideas with each other. 1.4 Project organization The following persons have been involved in this master thesis project: Simulation study and master thesis authors M.Sc.
Tony Larsson M.Sc. Nicklas Hedman Supervisor at Ericsson Telecom AB, Switchlab Tekn.Lic. Per Johansson Examiner at Lulea University of Technology Ph. D. Mikael Degermark Implementation study at Ericsson Mobile data design (ERV) in Gothenburg M.Sc. Johan Kopman M.Sc.
Jerry Svedlund Supervisor at ERV M.Sc. Essays About? Christoffer Kanljung Contribution of realistic scenarios Ph.D. student at Chalmers University of Technology: Bartosz Mielczarek 1 MObile Networking ARCHitectures 10 1.5 Disposition This report consists of 8 chapters and book two appendices. Chapters 1 and 2 explain the concept of ad-hoc networks and routing in general. Chapter 3 describes the different routing protocols, analyzes and compares them. Chapters 4 and 5 describe the simulator and the simulations that were made. Chapter 6 describes the essays career goals implementation study of AODV that was made in Gothenburg.
Chapter 7 concludes the whole report and chapter 8 is the waits book report references that we have used. The appendices contain some terminology, details about the implementation of essay on flower, AODV that we did for the simulator and some screenshots of the simulator. 1.6 Abbreviations AODV CBR CBRP DSDV DSR IEEE IETF LAN IP MAC MANET OLSR PDA QoS TCP TORA UDP WINET ZRP Ad-hoc On-demand Distance Vector Constant Bit Rate Cluster Based Routing Protocol Destination Sequenced Distance Vector Dynamic Source Routing Institute of hachiko, Electrical and Electronics Engineers Internet Engineering Task Force Local Area Network Internet Protocol Media Access Protocol Mobile Ad-hoc NETworks Optimized Link State Routing Protocol Personal Digital Assistant Quality of Service Transmission Control Protocol Temporally Ordered Routing Algorithm User Datagram Protocol Wireless InterNET Zone Routing Protocol 11 2 General Concepts 2.1 Wireless ad-hoc networks 2.1.1 General A wireless ad-hoc network is a collection of mobile/semi-mobile nodes with no pre-established infrastructure, forming a temporary network. Each of the nodes has a wireless interface and communicate with each other over either radio or infrared. Laptop computers and personal digital assistants that communicate directly with each other are some examples of nodes in an ad-hoc network.
Nodes in dahmen dissertation the adhoc network are often mobile, but can also consist of stationary nodes, such as access points to the Internet. Semi mobile nodes can be used to waits book, deploy relay points in areas where relay points might be needed temporarily. Figure 1 shows a simple ad-hoc network with three nodes. The outermost nodes are not within transmitter range of each other. However the middle node can be used to forward packets between the essay outermost nodes.
The middle node is waits book report acting as a router and the three nodes have formed an ad-hoc network. Figure 1: Example of a simple ad-hoc network with three participating nodes. An ad-hoc network uses no centralized administration. This is to be sure that the good about career network wont collapse just because one of the mobile nodes moves out of waits, transmitter range of the others. Nodes should be able to enter/leave the network as they wish. Because of the good essays career goals limited transmitter range of the nodes, multiple hops may be needed to waits book report, reach other nodes.
Every node wishing to participate in an ad-hoc network must be willing to forward packets for other nodes. Thus every node acts both as a host and as a router. A node can be viewed as an abstract entity consisting of a router and a set of affiliated mobile hosts (Figure 2). Career? A router is an entity, which, among other things runs a routing protocol. A mobile host is simply an waits IP-addressable host/entity in graduate nursing the traditional sense. Ad-hoc networks are also capable of handling topology changes and hachiko waits book report malfunctions in nodes. It is fixed through network reconfiguration. For instance, if a node leaves the network and essay garden causes link breakages, affected nodes can easily request new routes and waits the problem will be solved. This will slightly increase the delay, but the network will still be operational.
12 Wireless ad-hoc networks take advantage of the nature of the wireless communication medium. In other words, in a wired network the physical cabling is done a priori restricting the essay connection topology of the waits book report nodes. This restriction is not present in the wireless domain and, provided that two nodes are within transmitter range of each other, an on flower instantaneous link between them may form. Host Host Router Host Figure 2: Block diagram of a mobile node acting both as hosts and as router. Book Report? 2.1.2 Usage There is greener place essay no clear picture of what these kinds of networks will be used for.
The suggestions vary from document sharing at conferences to infrastructure enhancements and military applications. In areas where no infrastructure such as the Internet is available an ad-hoc network could be used by a group of book, wireless mobile hosts. This can be the case in areas where a network infrastructure may be undesirable due to reasons such as cost or convenience. Examples of essays career goals, such situations include disaster recovery personnel or military troops in cases where the normal infrastructure is either unavailable or destroyed. Other examples include business associates wishing to share files in an airport terminal, or a class of students needing to interact during a lecture. If each mobile host wishing to communicate is equipped with a wireless local area network interface, the group of hachiko report, mobile hosts may form an ad-hoc network.
Access to the Internet and access to dahmen, resources in networks such as printers are features that probably also will be supported. 2.1.3 Characteristics Ad-hoc networks are often characterized by a dynamic topology due to the fact that nodes change their physical location by moving around. Hachiko Book? This favors routing protocols that dynamically discover routes over good about goals conventional routing algorithms like distant vector and link state . Another characteristic is that a host/node have very limited CPU capacity, storage capacity, battery power and bandwidth, also referred to as a “thin client”. This means that the power usage must be limited thus leading to a limited transmitter range. The access media, the radio environment, also has special characteristics that must be considered when designing protocols for ad-hoc networks. One example of this may be unidirectional links. These links arise when for example two nodes have different strength on their transmitters, allowing only one of the host to hear the other, but can also arise from disturbances from the surroundings.
Multihop in a radio environment may result in hachiko waits report an overall transmit capacity gain and dahmen dissertation power gain, due to the squared relation between coverage and required output power. By using multihop, nodes can transmit the packets with a much lower output power. 13 2.2 Routing Because of the fact that it may be necessary to hop several hops (multi-hop) before a packet reaches the book report destination, a routing protocol is essay questions nursing needed. The routing protocol has two main functions, selection of routes for various source-destination pairs and the delivery of messages to their correct destination. The second function is conceptually straightforward using a variety of protocols and data structures (routing tables). This report is focused on selecting and finding routes. 2.2.1 Conventional protocols If a routing protocol is needed, why not use a conventional routing protocol like link state or distance vector? They are well tested and most computer communications people are familiar with them. The main problem with link-state and distance vector is that they are designed for a static topology, which means that they would have problems to converge to book, a steady state in an ad-hoc network with a very frequently changing topology. Link state and distance vector would probably work very well in an ad-hoc network with low mobility, i.e. Compare And Contrast Film Essay? a network where the topology is hachiko not changing very often. The problem that still remains is that link-state and essay on flower garden distance-vector are highly dependent on periodic control messages.
As the number of network nodes can be large, the potential number of hachiko waits report, destinations is also large. This requires large and frequent exchange of data among the network nodes. This is in contradiction with the fact that all updates in a wireless interconnected ad hoc network are transmitted over the air and thus are costly in resources such as bandwidth, battery power and CPU. Because both link-state and distance vector tries to greener essay, maintain routes to all reachable destinations, it is waits book report necessary to maintain these routes and frederick turner thesis about frontier this also wastes resources for hachiko waits book, the same reason as above. Another characteristic for conventional protocols are that they assume bi-directional links, e.g. Frederick Turner Thesis Frontier? that the transmission between two hosts works equally well in both directions. In the wireless radio environment this is not always the case. Because many of the proposed ad-hoc routing protocols have a traditional routing protocol as underlying algorithm, it is necessary to understand the basic operation for conventional protocols like distance vector, link state and source routing. 2.2.2 Link State In link-state routing , each node maintains a view of the complete topology with a cost for each link. To keep these costs consistent; each node periodically broadcasts the hachiko waits book link costs of its outgoing links to all other nodes using flooding. As each node receives this information, it updates its view of the network and career goals applies a shortest path algorithm to choose the next-hop for each destination. Some link costs in a node view can be incorrect because of long propagation delays, partitioned networks, etc.
Such inconsistent network topology views can lead to book report, formation of routing-loops. These loops are however short-lived, because they disappear in the time it takes a message to graduate essay nursing, traverse the diameter of the network. 2.2.3 Distance Vector In distance vector  each node only monitors the book cost of its outgoing links, but instead of broadcasting this information to all nodes, it periodically broadcasts to each of compare essay, its neighbors an report estimate of the shortest distance to every other node in essay on flower garden the network. The receiving nodes then use this information to waits book, recalculate the good about career routing tables, by using a shortest path algorithm. Compared to link-state, distance vector is waits book report more computation efficient, easier to implement and requires much less storage space. And Contrast? However, it is hachiko book report well known that distance vector can cause the formation of both short-lived and long-lived routing loops. The primary cause for this is that the nodes choose their next-hops in a completely distributed manner based on compare film, information that can be stale. 2.2.4 Source Routing Source routing  means that each packet must carry the complete path that the hachiko waits packet should take through the network. The routing decision is therefore made at the source. The advantage with this approach is that it is very easy to avoid routing loops.
The disadvantage is that each packet requires a slight overhead. 14 2.2.5 Flooding Many routing protocols uses broadcast to distribute control information, that is, send the control information from an origin node to all other nodes. A widely used form of broadcasting is flooding  and operates as follows. The origin node sends its information to its neighbors (in the wireless case, this means all nodes that are within transmitter range). The neighbors relay it to their neighbors and so on, until the packet has reached all nodes in the network.
A node will only compare film essay, relay a packet once and to hachiko waits, ensure this some sort of essay on flower garden, sequence number can be used. This sequence number is hachiko waits book increased for each new packet a node sends. 2.2.6 Classification Routing protocols can be classified  into different categories depending on their properties. On Flower Garden? N N N Centralized vs. Distributed Static vs.
Adaptive Reactive vs. Proactive One way to categorize the routing protocols is to divide them into centralized and hachiko book report distributed algorithms. Questions? In centralized algorithms, all route choices are made at waits book, a central node, while in distributed algorithms, the computation of routes is andreas shared among the network nodes. Another classification of routing protocols relates to whether they change routes in hachiko waits response to the traffic input patterns. In static algorithms, the route used by source-destination pairs is fixed regardless of traffic conditions. It can only change in response to a node or link failure. Greener? This type of book, algorithm cannot achieve high throughput under a broad variety of andreas, traffic input patterns. Most major packet networks uses some form of adaptive routing where the routes used to route between source-destination pairs may change in response to congestion A third classification that is more related to hachiko book report, ad-hoc networks is to classify the routing algorithms as either proactive or reactive. Proactive protocols attempt to continuously evaluate the routes within the network, so that when a packet needs to be forwarded, the route is already known and can be immediately used. The family of Distance-Vector protocols is an example of a proactive scheme.
Reactive protocols, on the other hand, invoke a route determination procedure on demand only. Thus, when a route is needed, some sort of global search procedure is employed. The family of essays career goals, classical flooding algorithms belongs to waits book, the reactive group. Proactive schemes have the advantage that when a route is needed, the delay before actual packets can be sent is very small. On the other side proactive schemes needs time to converge to a steady state. This can cause problems if the topology is changing frequently. 15 3 Ad-hoc routing protocols This chapter describes the different ad-hoc routing protocols that we have chosen to simulate and essay nursing analyze.
3.1 Desirable properties If the conventional routing protocols do not meet our demands, we need a new routing protocol. The question is what properties such protocols should have? These are some of the properties  that are desirable: Distributed operation The protocol should of hachiko report, course be distributed. It should not be dependent on graduate essay questions, a centralized controlling node. This is the case even for stationary networks. The difference is that nodes in an ad-hoc network can enter/leave the network very easily and because of mobility the network can be partitioned. Loop free To improve the overall performance, we want the routing protocol to guarantee that the routes supplied are loop-free. This avoids any waste of bandwidth or CPU consumption. Hachiko Report? Demand based operation To minimize the control overhead in the network and thus not wasting network resources more than necessary, the protocol should be reactive. This means that the protocol should only react when needed and that the andreas dahmen dissertation protocol should not periodically broadcast control information. Unidirectional link support The radio environment can cause the formation of unidirectional links.
Utilization of these links and book not only the bi-directional links improves the routing protocol performance. Security The radio environment is especially vulnerable to impersonation attacks, so to greener place essay, ensure the wanted behavior from the routing protocol, we need some sort of preventive security measures. Authentication and encryption is waits book probably the way to go and the problem here lies within distributing keys among the nodes in the ad-hoc network. There are also discussions about using IP-sec  that uses tunneling to transport all packets. Power conservation The nodes in an ad-hoc network can be laptops and on flower garden thin clients, such as PDAs that are very limited in waits report battery power and therefore uses some sort of stand-by mode to essay garden, save power.
It is therefore important that the routing protocol has support for these sleep-modes. Multiple routes To reduce the number of reactions to topological changes and congestion multiple routes could be used. Hachiko Waits Report? If one route has become invalid, it is possible that another stored route could still be valid and thus saving the career routing protocol from initiating another route discovery procedure. Waits Book? Quality of service support Some sort of Quality of Service support is probably necessary to incorporate into the routing protocol. Questions? This has a lot to do with what these networks will be used for. It could for instance be real-time traffic support. Book Report? None of the proposed protocols from MANET have all these properties, but it is necessary to remember that the protocols are still under development and are probably extended with more functionality. The primary function is still to find a route to the destination, not to find the best/optimal/shortest-path route. The remainder of this chapter will describe the different routing protocols and analyze them theoretically.
16 3.2 MANET IETF has a working group named MANET (Mobile Ad-hoc Networks)  that is working in the field of adhoc networks. Good Goals? They are currently developing routing specifications for ad-hoc IP networks that support scaling to a couple of hundred nodes. Their goal is to be finished in the end of year 1999 and hachiko then introduce these specifications to the Internet standard tracks. Even if MANET currently is frederick jackson thesis the american frontier working on routing protocols, it also serves as a meeting place and forum, so people can discuss issues concerning ad-hoc networks. Currently they have seven routing protocol drafts: N N N N N N N N AODV - Ad-hoc On Demand Distance Vector  ZRP - Zone Routing Protocol  TORA / IMEP - Temporally Ordered Routing Algorithm / Internet MANET Encapsulation Protocol  DSR - Dynamic Source Routing  CBRP - Cluster Based Routing Protocol  CEDAR - Core Extraction Distributed Ad hoc Routing  AMRoute – Ad-hoc Multicast Routing Protocol  OLSR - Optimized Link State Routing Protocol  Of these proposed protocols we have chosen to analyze AODV, DSR, ZRP, CBRP and TORA theoretically. We have also analyzed DSDV, which is a proactive approach, as opposed to the other reactive protocols. Waits Book? We have not analyzed AMRoute because it is a multicast routing protocol, neither CEDAR because it is primary a QoS routing protocol, nor OLSR, because it was submitted as an Internet draft so late. In those cases where a protocol supports both unicast and multicast routing we have only looked at the unicast routing part.
Of the essay on flower garden theoretically analyzed protocols we have done simulations on AODV and DSR. 3.3 Destination Sequenced Distance Vector - DSDV 3.3.1 Description DSDV  is a hop-by-hop distance vector routing protocol that in each node has a routing table that for all reachable destinations stores the next-hop and number of hachiko book report, hops for that destination. Frederick? Like distance-vector, DSDV requires that each node periodically broadcast routing updates. The advantage with DSDV over traditional distance vector protocols is that DSDV guarantees loop-freedom. To guarantee loop-freedom DSDV uses a sequence numbers to tag each route. The sequence number shows the freshness of a route and routes with higher sequence numbers are favorable. Report? A route R is andreas dahmen dissertation considered more favorable than R' if R has a greater sequence number or, if the routes have the hachiko waits same sequence number but R has lower hop-count. The sequence number is increased when a node A detects that a route to frederick turner about the american, a destination D has broken. So the next time node A advertises its routes, it will advertise the route to D with an infinite hop-count and a sequence number that is larger than before. DSDV basically is distance vector with small adjustments to make it better suited for ad-hoc networks.
These adjustments consist of triggered updates that will take care of topology changes in the time between broadcasts. To reduce the amount of hachiko waits, information in these packets there are two types of update messages defined: full and film essay incremental dump. The full dump carries all available routing information and hachiko waits book the incremental dump that only carries the information that has changed since the last dump. 3.3.2 Properties Because DSDV is dependent on periodic broadcasts it needs some time to good essays about career, converge before a route can be used. Waits? This converge time can probably be considered negligible in a static wired network, where the topology is not changing so frequently. In an ad-hoc network on place, the other hand, where the topology is expected to be very dynamic, this converge time will probably mean a lot of dropped packets before a valid route is detected. The periodic broadcasts also add a large amount of overhead into waits book the network. Andreas? 17 3.4 Ad-hoc On Demand Distance vector - AODV 3.4.1 Description The Ad Hoc On-Demand Distance Vector (AODV)  routing protocol enables multi-hop routing between participating mobile nodes wishing to establish and maintain an ad-hoc network. AODV is based upon the distance vector algorithm. The difference is that AODV is reactive, as opposed to proactive protocols like DV, i.e. AODV only requests a route when needed and hachiko waits book does not require nodes to maintain routes to destinations that are not actively used in communications.
As long as the endpoints of a communication connection have valid routes to essay questions, each other, AODV does not play any role. Features of this protocol include loop freedom and that link breakages cause immediate notifications to be sent to report, the affected set of nodes, but only that set. Additionally, AODV has support for multicast routing and avoids the place Bellman Ford counting to waits book, infinity problem . Greener? The use of destination sequence numbers guarantees that a route is fresh. The algorithm uses different messages to discover and maintain links. Whenever a node wants to try and find a route to another node, it broadcasts a Route Request (RREQ) to all its neighbors. Hachiko? The RREQ propagates through the network until it reaches the destination or a node with a fresh enough route to the destination. Then the and contrast essay route is made available by unicasting a RREP back to the source. The algorithm uses hello messages (a special RREP) that are broadcasted periodically to the immediate neighbors. These hello messages are local advertisements for the continued presence of the node and neighbors using routes through the broadcasting node will continue to book, mark the routes as valid. If hello messages stop coming from jackson thesis frontier, a particular node, the neighbor can assume that the node has moved away and hachiko book report mark that link to the node as broken and greener place notify the affected set of nodes by sending a link failure notification (a special RREP) to that set of book, nodes.
AODV also has a multicast route invalidation message, but because we do not cover multicast in this report we will not discuss this any further. Route table management AODV needs to keep track of the following information for each route table entry: N N N N N N N Destination IP Address: IP address for the destination node. Destination Sequence Number: Sequence number for this destination. Hop Count: Number of hops to the destination. Good Essays Career Goals? Next Hop: The neighbor, which has been designated to forward packets to the destination for this route entry. Lifetime: The time for which the waits report route is considered valid. Active neighbor list: Neighbor nodes that are actively using this route entry. Request buffer: Makes sure that a request is only processed once. Route discovery A node broadcasts a RREQ when it needs a route to a destination and dahmen dissertation does not have one available. This can happen if the route to the destination is unknown, or if a previously valid route expires. Waits? After broadcasting a RREQ, the place essay node waits for a RREP.
If the reply is not received within a certain time, the node may rebroadcast the RREQ or assume that there is waits no route to the destination. Forwarding of RREQs is done when the node receiving a RREQ does not have a route to essay nursing, the destination. It then rebroadcast the RREQ. The node also creates a temporary reverse route to the Source IP Address in its routing table with next hop equal to the IP address field of the neighboring node that sent the broadcast RREQ. This is done to keep track of a route back to the original node making the request, and might be used for an eventual RREP to find its way back to the requesting node. The route is temporary in the sense that it is valid for a much shorter time, than an waits book actual route entry. When the RREQ reaches a node that either is the destination node or a node with a valid route to the destination, a RREP is generated and unicasted back to the requesting node.
While this RREP is forwarded, a route is created to essays goals, the destination and hachiko waits book report when the good essays about RREP reaches the source node, there exists a route from the hachiko source to on flower, the destination. Book? 18 Route maintenance When a node detects that a route to a neighbor no longer is valid, it will remove the routing entry and send a link failure message, a triggered route reply message to the neighbors that are actively using the route, informing them that this route no longer is valid. For this purpose AODV uses a active neighbor list to keep track of the neighbors that are using a particular route. The nodes that receive this message will repeat this procedure. The message will eventually be received by the affected sources that can chose to either stop sending data or requesting a new route by sending out a new RREQ. 3.4.2 Properties The advantage with AODV compared to classical routing protocols like distance vector and link-state is that AODV has greatly reduced the number of routing messages in compare film essay the network. AODV achieves this by using a reactive approach. This is probably necessary in hachiko report an ad-hoc network to get reasonably performance when the topology is changing often. Frederick The American Frontier? AODV is hachiko book also routing in frederick jackson about frontier the more traditional sense compared to for instance source routing based proposals like DSR (see 3.5). The advantage with a more traditional routing protocol in an ad-hoc network is that connections from the ad-hoc network to a wired network like the Internet is most likely easier.
The sequence numbers that AODV uses represents the freshness of a route and hachiko book is increased when something happens in the surrounding area. The sequence prevents loops from being formed, but can however also be the dahmen cause for new problems. Waits Book Report? What happens for instance when the sequence numbers no longer are synchronized in the network? This can happen when the essay questions nursing network becomes partitioned, or the sequence numbers wrap around. AODV only support one route for each destination. It should however be fairly easy to modify AODV, so that it supports several routes per destination. Hachiko Waits Report? Instead of compare, requesting a new route when an old route becomes invalid, the next stored route to hachiko waits report, that destination could be tried.
The probability for essay nursing, that route to still be valid should be rather high. Although the Triggered Route Replies are reduced in number by only sending the Triggered Route Replies to affected senders, they need to book report, traverse the whole way from the failure to the senders. This distance can be quite high in numbers of hops. Turner Thesis About Frontier? AODV sends one Triggered RREP for hachiko waits book report, every active neighbor in the active neighbor list for all entries that have been affected of dahmen, a link failure. This can mean that each active neighbor can receive several triggered RREPs informing about the same link failure, but for different destinations, if a large fraction of the network traffic is routed through the hachiko book same node and this node goes down. An aggregated solution would be more appropriate here.
AODV uses hello messages at andreas dahmen dissertation, the IP-level. Book Report? This means that AODV does not need support from the link layer to work properly. It is however questionable if this kind of protocol can operate with good performance without support from the link layer. The hello messages adds a significant overhead to the protocol. AODV does not support unidirectional links.
When a node receives a RREQ, it will setup a reverse route to the source by place essay using the node that forwarded the RREQ as nexthop. This means that the route reply, in most cases is unicasted back the hachiko waits report same way as the route request used. Unidirectional link support would make it possible to utilize all links and not only the bi-directional links. It is however questionable if unidirectional links are desirable in greener a real environment. The acknowledgements in the MAC protocol IEEE 802.11 would for report, instance not work with unidirectional links. 19 3.5 Dynamic Source Routing - DSR 3.5.1 Description Dynamic Source Routing (DSR)  also belongs to the class of reactive protocols and allows nodes to compare film essay, dynamically discover a route across multiple network hops to any destination. Source routing means that each packet in its header carries the hachiko waits complete ordered list of compare film, nodes through which the packet must pass. DSR uses no periodic routing messages (e.g. no router advertisements), thereby reducing network bandwidth overhead, conserving battery power and avoiding large routing updates throughout the book report ad-hoc network. Instead DSR relies on support from the MAC layer (the MAC layer should inform the routing protocol about link failures). The two basic modes of essay, operation in report DSR are route discovery and route maintenance. Route discovery Route discovery is the mechanism whereby a node X wishing to good about, send a packet to Y, obtains the source route to Y. Node X requests a route by broadcasting a Route Request (RREQ) packet.
Every node receiving this RREQ searches through its route cache for a route to the requested destination. Book Report? DSR stores all known routes in its route cache. If no route is found, it forwards the RREQ further and adds its own address to the recorded hop sequence. This request propagates through the network until either the career goals destination or a node with a route to the destination is reached. When this happen a Route Reply (RREP) is unicasted back to waits report, the originator. Andreas Dahmen Dissertation? This RREP packet contains the sequence of network hops through which it may reach the target. Waits? In Route Discovery, a node first sends a RREQ with the maximum propagation limit (hop limit) set to compare and contrast essay, zero, prohibiting its neighbors from rebroadcasting it.
At the cost of a single broadcast packet, this mechanism allows a node to query the route caches of all its neighbors. Book? Nodes can also operate their network interface in promiscuous mode, disabling the interface address filtering and causing the network protocol to receive all packets that the interface overhears. These packets are scanned for useful source routes or route error messages and then discarded. Andreas Dahmen Dissertation? The route back to the originator can be retrieved in several ways. Book? The simplest way is to essay on flower garden, reverse the waits report hop record in the packet. However this assumes symmetrical links. Compare And Contrast? To deal with this, DSR checks the route cache of the replying node. Hachiko Waits? If a route is found, it is used instead.
Another way is to piggyback the reply on a RREQ targeted at the originator. This means that DSR can compute correct routes in andreas dahmen dissertation the presence of asymmetric (unidirectional) links. Once a route is found, it is stored in the cache with a time stamp and the route maintenance phase begins. Route maintenance Route maintenance is the mechanism by which a packet sender S detects if the hachiko waits network topology has changed so that it can no longer use its route to the destination D. This might happen because a host listed in a source route, move out of wireless transmission range or is turned off making the route unusable. A failed link is detected by either actively monitoring acknowledgements or passively by running in promiscuous mode, overhearing that a packet is essay questions nursing forwarded by a neighboring node. Waits Report? When route maintenance detects a problem with a route in dahmen use, a route error packet is sent back to the source node. When this error packet is received, the hop in error is removed from this hosts route cache, and report all routes that contain this hop are truncated at this point.
3.5.2 Properties DSR uses the key advantage of source routing. Intermediate nodes do not need to maintain up-to-date routing information in order to route the frederick jackson turner thesis about the american packets they forward. Hachiko Waits Book Report? There is also no need for periodic routing advertisement messages, which will lead to reduce network bandwidth overhead, particularly during periods when little or no significant host movement is taking place. Battery power is also conserved on the mobile hosts, both by not sending the advertisements and by not needing to receive them, a host could go down to sleep instead. This protocol has the advantage of learning routes by scanning for information in packets that are received. Questions Nursing? A route from A to hachiko waits report, C through B means that A learns the route to C, but also that it will learn the route to B. The source route will also mean that B learns the route to A and C and that C learns the route to A and dissertation B. This form of active learning is very good and hachiko waits book reduces overhead in the network. 20 However, each packet carries a slight overhead containing the turner source route of the packet. This overhead grows when the packet has to go through more hops to reach the destination. So the packets sent will be slightly bigger, because of the overhead.
Running the interfaces in promiscuous mode is a serious security issue. Since the report address filtering of the interface is turned off and all packets are scanned for garden, information. A potential intruder could listen to all packets and hachiko waits book scan them for useful information such as passwords and credit card numbers. Applications have to provide the security by film encrypting their data packets before transmission. Waits Book? The routing protocols are prime targets for impersonation attacks and must therefore also be encrypted. One way to place, achieve this is to waits book, use IPsec . DSR also has support for good essays about career, unidirectional links by the use of piggybacking the source route a new request. This can increase the waits book performance in scenarios where we have a lot of graduate essay, unidirectional links.
We must however have a MAC protocol that also supports this. 3.6 Zone Routing Protocol - ZRP 3.6.1 Description Zone Routing Protocol (ZRP)  is a hybrid of a reactive and a proactive protocol. It divides the network into several routing zones and specifies two totally detached protocols that operate inside and between the routing zones. The Intrazone Routing Protocol (IARP) operates inside the routing zone and learns the minimum distance and routes to hachiko book, all the nodes within the zone. The protocol is not defined and can include any number of proactive protocols, such as Distance Vector or link-state routing. Different zones may operate with different intrazone protocols as long as the protocols are restricted to those zones. A change in topology means that update information only propagates within the greener affected routing zones as opposed to affecting the entire network. Waits? The second protocol, the Interzone Routing Protocol (IERP) is reactive and essay on flower garden is used for finding routes between different routing zones.
This is useful if the destination node does not lie within the routing zone. The protocol then broadcasts (i.e. Waits? bordercasts) a Route REQuest (RREQ) to all border nodes within the routing zone, which in essay on flower garden turn forwards the request if the destination node is not found within their routing zone. This procedure is repeated until the requested node is found and a route reply is sent back to the source indicating the route. IERP uses a Bordercast Resolution Protocol (BRP)  that is included in hachiko ZRP. Garden? BRP provides bordercasting services, which do not exist in hachiko waits report IP. Bordercasting is the process of sending IP datagrams from one node to all its peripheral nodes.
BRP keeps track of the peripheral nodes and resolves a border cast address to the individual IP-addresses of the peripheral nodes. The message that was bordercasted is graduate questions then encapsulated into a BRP packet and sent to each peripheral node. Routing Zone A routing zone is defined as a set of waits report, nodes, within a specific minimum distance in number of hops from the node in question. The distance is referred to as the zone radius. In the example network (Figure 3), node S, A, F, B, C, G and andreas dissertation H, all lie within a radius of two from node F. Hachiko Book? Even though node B also has a distance of 3 hops from node F, it is dahmen dissertation included in the zone since the shortest distance is only 2 hops. Border nodes or peripheral nodes are nodes whose minimum distance to the node in hachiko report question is equal exactly to the zone radius. In Figure 3, nodes B and F are border nodes to S. Consider the network in Figure 3. Place Essay? Node S wants to send a packet to node D. Since node D is not in the routing zone of S, a route request is sent to report, the border nodes B and F. Each border node checks to see if D is in their routing zone. Dissertation? Neither B nor F finds the requested node in their routing zone; thus the request is hachiko waits book forwarded to the respectively border nodes. F sends the request to S, B, C and H while B sends the request to on flower, S, F, E and G. Now the requested node D is found within the routing zone of both C and E thus a reply is generated and waits sent back towards the graduate essay source node S. 21 B E A Zone for D C S D F Zone for S G H Zone for hachiko waits report, F Figure 3: Network using ZRP. The dashed squares show the routing zones for nodes S and good essays about goals D. To prevent the requests from going back to previously queried routing zone, a Processed Request List is used. This list stores previously processed requests and if a node receives a request that it already has processed, it is simply dropped.
3.6.2 Properties ZRP is a very interesting protocol and hachiko report can be adjusted of its operation to the current network operational conditions (e.g. change the routing zone diameter). However this is not done dynamically, but instead it is suggested that this zone radius should be set by the administration of the network or with a default value by the manufacturer. The performance of this protocol depends quite a lot on frederick turner, this decision. Since this is a hybrid between proactive and reactive schemes, this protocol use advantages from both. Hachiko Waits? Routes can be found very fast within the routing zone, while routes outside the zone can be found by efficiently querying selected nodes in and contrast essay the network. One problem is hachiko report however that the proactive intrazone routing protocol is not specified. The use of different intrazone routing protocols would mean that the nodes would have to compare essay, support several different routing protocols. This is hachiko report not a good idea when dealing with thin clients. It is better to use the same intrazone routing protocol in the entire network. ZRP also limits propagation of good essays goals, information about topological changes to hachiko report, the neighborhood of the change only (as opposed to a fully proactive scheme, which would basically flood the entire network when a change in topology occurred).
However, a change in topology can affect several routing zones. 3.7 Temporally-Ordered Routing Algorithm - TORA 3.7.1 Description Temporally Ordered Routing Algorithm (TORA)  is a distributed routing protocol. The basic underlying algorithm is one in a family referred to as link reversal algorithms. TORA is designed to minimize reaction to topological changes. A key concept in its design is that control messages are typically localized to a very small set of nodes. It guarantees that all routes are loop-free (temporary loops may form), and typically provides multiple routes for any source/destination pair.
It provides only the routing mechanism and depends on Internet MANET Encapsulation Protocol (IMEP ) for other underlying functions. TORA can be separated into three basic functions: creating routes, maintaining routes, and erasing routes. The creation of routes basically assigns directions to links in film an undirected network or portion of the network, building a directed acyclic graph (DAG) rooted at the destination (See Figure 4). 22 D Figure 4: Directed acyclic graph rooted at destination. Report? TORA associates a height with each node in the network. All messages in the network flow downstream, from a node with higher height to a node with lower height. Routes are discovered using Query (QRY) and Update (UPD) packets. Essay Questions? When a node with no downstream links needs a route to hachiko waits book report, a destination, it will broadcast a QRY packet. On Flower? This QRY packet will propagate through the network until it reaches a node that has a route or the hachiko waits destination itself. Such a node will then broadcast a UPD packet that contains the node height. Every node receiving this UPD packet will set its own height to a larger height than specified in compare essay the UPD message.
The node will then broadcast its own UPD packet. This will result in a number of directed links from the originator of the QRY packet to the destination. This process can result in multiple routes. Maintaining routes refers to reacting to topological changes in the network in a manner such that routes to the destination are re-established within a finite time, meaning that its directed portions return to book report, a destination-oriented graph within a finite time. Upon detection of a network partition, all links in the portion of the network that has become partitioned from the destination are marked as undirected to andreas, erase invalid routes. The erasing of routes is hachiko book report done using clear (CLR) messages.
3.7.2 Properties The protocols underlying link reversal algorithm will react to link changes through a simple localized single pass of the distributed algorithm. This prevents CLR packets to propagate too far in the network. A comparison made by the CMU Monarch project has however shown that the jackson frontier overhead in TORA is quite large because of the use of IMEP. The graph is hachiko waits report rooted at the destination, which has the lowest height. Greener Essay? However, the source originating the QRY does not necessarily have the hachiko book highest height. This can lead to place, the situation, where multiple routes are possible from the source to the destination, but only one route will be discovered. The reason for hachiko waits report, this is that the height is initially based on the distance in number of hops from the destination.
23 3.8 Internet MANET Encapsulation Protocol - IMEP 3.8.1 Description IMEP  is a protocol designed to support the frederick thesis about operation of many routing protocols in hachiko waits book Ad-hoc networks. The idea is to have a common general protocol that all routing protocols can make use of (see Figure 5). It incorporates many common mechanisms that the upper-layer protocol may need. These include: N N N N N Link status sensing Control message aggregation and frederick turner thesis about the american frontier encapsulation Broadcast reliability Network-layer address resolution Hooks for interrouter security authentication procedures IMEP also provides an architecture for MANET router identification, interface identification and addressing. IMEPs purpose is to improve overall performance by reducing the number of hachiko waits book, control messages and to andreas dissertation, put common functionality into one unified, generic protocol useful to all upper-level routing protocols. Hachiko Waits Report? Routing IMEP IP Figure 5: IMEP in good essays about goals the protocol stack. Of the currently purposed protocols, only hachiko report, TORA and OLSR use IMEP. It must however be noted that TORA and place IMEP where designed by the same author. 3.8.2 Properties The idea to have a general protocol for common basic features is good, but from a performance point of view this is not such a good idea. It adds another layer to the protocol stack. As the work by hachiko waits book the CMU Monarch projects has shown , IMEP generates a lot of overhead, mainly because of IMEPs neighbor discovery mechanism that generates at least one hello message per frederick thesis about the american frontier, second, but also because of the reliable in-order delivery of the packets that IMEP provides.
3.9 Cluster Based Routing Protocol - CBRP 3.9.1 Description The idea behind CBRP  is to divide the nodes of an ad-hoc network into a number of overlapping or disjoint clusters. One node is elected as cluster head for each cluster. This cluster head maintains the membership information for the cluster. Inter-cluster routes (routes within a cluster) are discovered dynamically using the membership information. 24 CBRP is based on source routing, similar to DSR. Waits? This means that intracluster routes (routes between clusters) are found by flooding the network with Route Requests (RREQ). The difference is that the cluster structure generally means that the number of nodes disturbed are much less. Flat routing protocols, i.e. only andreas dahmen dissertation, one level of hierarchy, might suffer from excessive overhead when scaled up. CBRP is like the waits book report other protocols fully distributed. This is necessary because of the very dynamic topology of the ad-hoc network. Furthermore, the protocol takes into consideration the existence of unidirectional links.
Link sensing Each node in CBRP knows its bi-directional links to its neighbors as well as unidirectional links from its neighbors to itself. To handle this, each node must maintain a Neighbor Table (see Table 1). Table 1: Neighbor ID Neighbor 1 Neighbor 2 … Neighbor n Neighbor table. Link status Bi/unidirectional link to me Bi/unidirectional link to me … Bi/unidirectional link to me Role Is 1 a cluster head or member Is 2 a cluster head or member … Is n a cluster head or member Each node periodically broadcasts its neighbor table in a hello message. The hello message contains the node ID, the nodes role (cluster head, cluster member or undecided) and the neighbor table. Garden? The hello messages are used to update the neighbor tables at each node. Book? If no hello message is received from a certain node, that entry will be removed from the table. Clusters The cluster formation algorithm is andreas dahmen dissertation very simple, the node with lowest node ID is hachiko book report elected as the cluster head. About Career? The nodes use the information in hachiko waits report the hello messages to and contrast film, decide whether or not they are the cluster heads. The cluster head regards all nodes it has bi-directinal links to waits report, as its member nodes.
A node regards itself as a member node to a particular cluster if it has a bi-directinal link to the cluster head. It is possible for a node to belong to several clusters. Cluster 1 Cluster 2 3 4 Cluster head Cluster head 1 2 6 Figure 6: 5 Bi-directional linked clusters. 25 Clusters are identified by their respective cluster heads, which means that the cluster head must change as infrequently as possible. Graduate Essay Nursing? The algorithm is therefore not a strict lowest ID clustering algorithm. A noncluster head never challenges the status of an existing cluster head. Only when two cluster-heads move next to hachiko, each other, will one of them lose the role as cluster head. In Figure 6 node 1 is cluster head for cluster 1 and node 2 is turner about the american frontier cluster head for hachiko book report, cluster 2. Routing Routing in CBRP is based on source routing and the route discovery is done, by flooding the network with Route Requests (RREQ). The clustering approach however means that fewer nodes are disturbed. This, because only the questions cluster heads are flooded.
If node X needs a route to node Y, node X will send out a RREQ, with a recorded source route listing only waits book report, itself initially. Any node forwarding this packet will add its own ID in this RREQ. Dahmen Dissertation? Each node forwards a RREQ only once and it never forwards it to node that already appears in hachiko waits book report the recorded route. In CBRP, a RREQ will always follow a route with the following pattern: Source-Cluster head-Gateway-Cluster head-Gateway- . -Destination A gateway node for a cluster is a node that knows that it has a bi-directional or a unidirectional link to a node in another cluster. Dahmen? In Figure 6, node 6 is waits report gateway node for cluster 1 and node 4 is gateway node for cluster 2. The source unicasts the RREQ to its cluster head. Each cluster-head unicasts the RREQ to each of its bidirectionally linked neighbor clusters, which has not already appeared in the recorded route through the on flower garden corresponding gateway. There does not necessarily have to be an actual bi-directional link to a bi-directional linked neighbor cluster. For instance, in Figure 6 cluster 1 has a unidirectional link to waits, cluster 2 through node 3 and essays career cluster 2 has a unidirectional link to cluster 1 through node 5, and the clusters are therefore bidirectional linked neighbor clusters. Book? This procedure continues until the target is found or another node can supply the route. When the RREQ reaches the target, the target may chose to memorize the dahmen reversed route to the source. It then copies the recorded route to book, a Route Reply packet and sends it back to the source.
3.9.2 Properties This protocol has a lot of and contrast, common features with the earlier discussed protocols. It has a route discovery and hachiko waits report route removal operation that has a lot in common with DSR and AODV. Graduate Questions Nursing? The clustering approach is probably a very good approach when dealing with large ad-hoc networks. The solution is hachiko report more scalable than the greener essay other protocols, because it uses the waits clustering approach that limits the number of messages that need to be sent. CBRP also has the advantage that it utilizes unidirectional links.
One remaining question is however how large each cluster should be. This parameter is critical to graduate, how the protocol will behave. 3.10 Comparison So far, the protocols have been analyzed theoretically. Table 2 summarizes and compares the report result from these theoretical/qualitative analyses and shows what properties the protocols have and do not have. As it can be seen from Table 2, none of the protocols support power conservation or Quality of Service. This is however work in progress and jackson turner will probably be added to hachiko waits book, the protocols. All protocols are distributed, thus none of the protocols is dependent on about, a centralized node and can therefore easily reconfigure in the event of topology changes.
26 Table 2: Comparison between ad-hoc routing protocols. DSDV AODV DSR ZRP Loop-free Yes Yes Yes Yes Multiple routes Distributed Reactive Unidirectional link support QoS Support Multicast Security Power conservation Periodic broadcasts No Yes No No No No No No Yes No Yes Yes No No Yes No No Yes Yes Yes Yes Yes No No No No No No Yes Partially No No No No No Yes Requires reliable or sequenced data No No No No TORA/ IMEP No, short lived loops Yes Yes Yes No No No No No Yes (IMEP) Yes CBRP Yes Yes Yes Yes Yes No No No No Yes No DSDV is the waits book report only proactive protocol in essays about this comparison. It is also the protocol that have most in common with traditional routing protocol in wired networks. The sequence numbers were added to ensure loop-free routes. Hachiko Waits Book? DSDV will probably be good enough in networks, which allows the protocol to converge in reasonable time. This however means that the film essay mobility cannot be too high. The authors of report, DSDV came to the same conclusions and andreas dissertation designed AODV, which is a reactive version of DSDV. They also added multicast capabilities, which will enhance the performance significantly when one node communicates with several nodes.
The reactive approach in AODV has many similarities with the reactive approach of DSR. They both have a route discovery mode that uses request messages to find new routes. Hachiko? The difference is film essay that DSR is report based on source routing and will learn more routes than AODV. Essay? DSR also has the advantage that it supports unidirectional links. DSR has however one major drawback and it is the source route that must be carried in each packet. Hachiko? This can be quite costly, especially when QoS is going to be used. ZRP and CBRP are two very interesting proposals that divide the network into several zones/clusters. This approach is probably a very good solution for large networks. Within the zones/clusters they have a more proactive scheme and between the zones/clusters they have a reactive scheme that have many similarities with the operation of AODV and about career goals DSR. Waits Book? They have for good, instance a route discovery phase that sends request through the network. The difference between ZRP and CBRP is book report how the network is garden divided.
In ZRP all zones are overlapping and in CBRP clusters can be both overlapping and disjoint. None of the presented protocols are adaptive, meaning that the protocols do not take any smart routing decisions when the traffic load in the network is taken into hachiko waits consideration. And Contrast? As a route selection criteria the proposed protocols use metrics such as shortest number of waits, hops and quickest response time to a request. This can lead to greener essay, the situation where all packets are routed through the same node even if there exist better routes where the traffic load is not as large. 27 4 Simulation Environment The simulator we have used to simulate the ad-hoc routing protocols in is the Network Simulator 2 (ns)  from Berkeley. Waits? To simulate the and contrast film essay mobile wireless radio environment we have used a mobility extension to ns that is hachiko waits report developed by compare the CMU Monarch project at Carnegie Mellon University. 4.1 Network Simulator Network simulator 2 is the result of an on-going effort of book report, research and development that is good administrated by researchers at Berkeley. It is waits a discrete event simulator targeted at networking research. It provides substantial support for greener essay, simulation of hachiko report, TCP, routing, and multicast protocols. Andreas Dahmen Dissertation? The simulator is written in C++ and a script language called OTcl2.
Ns uses an report Otcl interpreter towards the user. This means that the user writes an OTcl script that defines the network (number of nodes, links), the about traffic in the network (sources, destinations, type of traffic) and which protocols it will use. This script is waits report then used by essay ns during the simulations. The result of the simulations is an hachiko waits output trace file that can be used to place essay, do data processing (calculate delay, throughput etc) and to visualize the simulation with a program called Network Animator (NAM). See Appendix C for a screenshot of NAM. Waits Book? NAM is a very good visualization tool that visualizes the and contrast essay packets as they propagate through the hachiko report network. Graduate Essay? An overview of how a simulation is done in ns is shown in Figure 7. Otcl script Network Simulator 2 Output Data processing Network Animator Figure 7: Network simulator 2. The current version3 of the Network simulator does not support mobile wireless environments. The Network simulator alone is only intended for stationary networks with wired links. This caused us some problems in the beginning of this master thesis.
We needed mobility and therefore started to design and implement a mobility model that would extend the simulator. Hachiko Waits Report? We also started to implement the AODV protocol. Essay Garden? This implementation of AODV is compatible with NAM and therefore gives a good picture of how AODV behaves. It is very easy to follow for instance the route discovery procedure. About two months later, in hachiko report August 1998, two separate mobility extensions were released. These extensions had everything that we wanted from an extension, so we decided to compare film essay, use one of them. This however meant that the implementation of AODV that we made earlier no longer was compatible and hachiko waits book report had to be ported. 2 3 Object Tool Command Language Network simulator 2.1b3 28 4.2 Mobility extension There currently exist two mobility extensions to ns.
These are: N N Wireless mobility extension developed by the CMU Monarch projects . Mobility support, mobile IP and wireless channel support developed by C. Perkins at Sun Microsystems . The ns group at Berkeley has as intention to integrate both these extensions to ns. Goals? This work is however not complete yet. We have chosen to use the CMU Monarch extension, because this extension is targeted at ad-hoc networks. The version of the extension that we have worked with4 adds the following features5 to book, the Network simulator.
Node mobility Each mobile node is an jackson turner thesis about frontier independent entity that is responsible for hachiko, computing its own position and velocity as a function of time. Nodes move around according to a movement pattern specified at compare film, the beginning of the simulation. Realistic physical layers Propagation models are used to decide how far packets can travel in air. These models also consider propagation delays, capture effects and carrier sense . MAC 802.11 An implementation of the report IEEE 802.11 Media Access Protocol (MAC)  protocol was included in the extension. The MAC layer handles collision detection, fragmentation and acknowledgements. This protocol may also be used to detect transmission errors. 802.11 is a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol. It avoids collisions by graduate questions nursing checking the channel before using it. If the channel is free, it can start sending, if not, it must wait a random amount of time before checking again. Hachiko Waits? For each retry an exponential backoff algorithm will be used.
In a wireless environment it cannot be assumed that all stations hear each other. If a station senses the medium, as free, it does not necessarily mean that the medium is free around the receiver area. This problem is known as the hidden terminal problem and to overcome these problems the Collision Avoidance mechanism together with a positive acknowledgement scheme is used. The positive acknowledgement scheme means that the receiver sends an graduate acknowledgement when it receives a packet. The sender will try to retransmit this packet until it receives the acknowledgement or the number of retransmits exceeds the hachiko waits book maximum number of retransmits. 802.11 also support power saving and security. Power saving allows packets to be buffered even if the system is asleep. Security is provided by an algorithm called Wired Equivalent Privacy (WEP). It supports authentication and encryption. WEP is a Pseudo Random Number Generator (PRNG) and is based on RSAs RC4. One of the most important features of 802.11 is the jackson turner thesis frontier ad-hoc mode, which allows users to build up Wireless LANs without an infrastructure (without an access point).
Address Resolution Protocol The Address Resolution Protocol, ARP  is implemented. ARP translates IP-addresses to hardware MAC addresses. This takes place before the packets are sent down to report, the MAC layer. Ad-hockey Ad-hockey is an application that makes it possible to visualize the frederick jackson thesis the american frontier mobile nodes as they move around and send/receives packets. Ad-hockey can also be used as a scenario generator tool to create the hachiko waits report input files necessary for the simulations. This is done, by essay nursing positioning nodes in hachiko waits report a specified area.
Each node is then given a movement pattern consisting of movement directions at different waypoints, speed, pause times and communication patterns. Screenshots of ad-hockey can be seen in Appendix C. 4 Version 1.0.0-beta, released in the middle of August. At the end of November 1998, the dahmen dissertation CMU Monarch projects released version 1.1.0 of the extension. This new version contains some bug fixes and implementations of the AODV and TORA protocols. Waits Book Report? 5 29 Radio network interfaces This is a model of the hardware that actually transmits the greener essay packet onto the channel with a certain power and modulation scheme .
Transmission power The radius of the transmitter with an omni-directional antenna is about 250 meters in this extension. Antenna gain and receiver sensitivity Different antennas are available for simulations. Ad-hoc routing protocols Both DSR and DSDV have been implemented and added to this extension. Hachiko Book Report? 4.2.1 Shared media The extension is based on a shared media model (Ethernet in career goals the air). This means that all mobile nodes have one or more network interfaces that are connected to a channel (see Figure 8). A channel represents a particular radio frequency with a particular modulation and coding scheme. Hachiko? Channels are orthogonal, meaning that packets sent on essays about career, one channel do not interfere with the transmission and reception of packets on book, another channel. The basic operation is as follows, every packet that is sent / put on the channel is received / copied to all mobile nodes connected to the same channel.
When a mobile nodes receive a packet, it first determines if it possible for it to receive the packet. This is determined by the radio propagation model, based on the transmitter range, the distance that the packet has traveled and the amount of essays about career, bit errors. Mobile Node Mobile Node Mobile Node Channel Figure 8: Shared media model. 4.2.2 Mobile node Each mobile node (Figure 9) makes use of a routing agent for the purpose of hachiko report, calculating routes to other nodes in frederick jackson turner about the american the ad-hoc network. Packets are sent from the application and are received by the routing agent. The agent decides a path that the packet must travel in hachiko book report order to reach its destination and place stamps it with this information. It then sends the packet down to the link layer. The link layer level uses an Address Resolution Protocol (ARP) to decide the hardware addresses of neighboring nodes and map IP addresses to their correct interfaces. When this information is known, the packet is report sent down to the interface queue and awaits a signal from the essay on flower Multiple Access Control (MAC) protocol.
When the hachiko waits book MAC layer decides it is ok to compare and contrast essay, send it onto report the channel, it fetches the packet from the queue and hands it over to the network interface which in turn sends the packet onto the radio channel. This packet is andreas copied and is delivered to all network interfaces at the time at which the first bit of the waits book report packet would begin arriving at the interface in a physical system. Each network interface stamps the packet with the andreas dahmen receiving interfaces properties and then invokes the propagation model. The propagation model uses the transmit and receive stamps to determine the power with which the interface will receive the packet. The receiving network interfaces then use their properties to determine if they actually successfully received the hachiko waits packet, and sends it to the MAC layer if appropriate. If the MAC layer receives the packet error- and collision- free, it passes the packet to the mobiles entry point. About Career? From there it reaches a demultiplexer, which decides if the waits packet should be forwarded again, or if it has reached its destination node. If the destination node is reached, the packet is sent to a port demultiplexer, which decides to what application the packet should be delivered. Compare And Contrast Essay? If the packet should be forwarded again the routing agent will be called and the procedure will be repeated. 30 Entry point M U X Application Routing Agent Link Layer ARP Queue MAC Propagation model Network Interface Channel Figure 9: A mobile node.
4.3 Simulation overview A typical simulation with ns and the mobility extension is shown in hachiko waits Figure 10. Basically it consists of generating the following input files to ns: N N A scenario file that describes the movement pattern of the dahmen nodes. A communication file that describes the traffic in waits book the network. These files can be generated by greener drawing them by hand using the hachiko book visualization tool Ad-hockey (see 4.2) or by generating completely randomized movement and communication patterns with a script. These files are then used for the simulation and greener place essay as a result from this, a trace file is hachiko generated as output. Prior to the simulation, the parameters that are going to be traced during the simulation must be selected. The trace file can then be scanned and analyzed for the various parameters that we want to measure.
This can be used as data for plots with for greener place essay, instance Gnuplot. The trace file can also be used to visualize the simulation run with either Ad-hockey or Network animator. Book Report? 31 Scenario generation Scenario file Communication file Mobility extension Network Simulator 2 Output files Data processing Ad-hockey GnuPlot Figure 10: Network animator Simulation overview. 4.4 Modifications To be able to compare and contrast essay, use ns for book report, the simulations, we had to do some modifications. And Contrast Film? First of all, we did not have the routing protocols we wanted to simulate, so one of the first steps was to implement the protocols. 4.4.1 AODV We have implemented the book report AODV protocol (for more details, see appendix B). Graduate Essay? The implementation is done according to the AODV draft  released in hachiko waits August 1998. It must however be noted that a new version of the draft  was released in the end of compare and contrast essay, November 1998. The new draft contains some changes that would enhance the performance. Hachiko Waits Book Report? These changes that affect the unicast routing part is primarily: N N Reduced or complete elimination of hello messages. Essay Questions? Updates to important parameters to reflect recent simulation experiences.
To be able to test how the hello messages and link layer support affects the behavior of the protocol we have implemented three versions: N N N AODV with only IP-based hello messages AODV with only hachiko report, Link Layer notification of broken links AODV with both IP-based hello messages and greener Link layer notification of broken links The implementation of the different versions has some major differences that will affect the performance. Hachiko Book? First of all AODV with only MAC-layer support will not get the routes to the neighbors installed in the routing table, neither will it update the routes to the neighbor who forwarded a message to you. Both AODV versions that have hello messages will have this neighbor detection process that keeps track of the neighbors. Frederick Turner About? This means that the protocols with this feature will have more information in the 32 routing tables. Hachiko Waits Book? Without this support, buffering of the packets may be necessary while a request is sent out in search for film essay, a node that could be a neighbor. It must however be noted that the removal of hello messages somewhat changes the book behavior of the AODV protocol. The hello messages add overhead to the protocol, but also gives us some prior knowledge of link breakages. Removing the hello messages makes the protocol completely on-demand, broken links can only be detected when actually sending something on the broken link. The DSR implementation that was included in the mobility extension used a sendbuffer that buffered all packets that the application sent while the routing protocol searched for a route. To get a fair comparison of the protocols we implemented the on flower same feature for AODV. This buffer can hold 64 packets and packets are allowed to stay in the buffer for 8 seconds.
The parameters that can be adjusted for AODV and the values we have used is shown in Table 3. Some of these parameters are very important and affects the performance of the protocol in drastic ways. Report? The hello interval is maybe the most important parameter when dealing with AODV that uses hello messages. If the interval is too long, link breakages would not be detected fast enough, but if the place essay interval is to hachiko waits report, short, a great amount of extra control overhead would be added. Essays Goals? Most of the book parameters in Table 3 are obvious. The maximum rate for sending replies prevents a node to do a triggered route reply storm.
This means that AODV in each node is only allowed to send one triggered RREP per second for each broken route. This could for instance happen if a forwarding node receives a lot of data packets that the node no longer has a route for. In this case the greener essay node should only send a triggered RREP, as a response to the first data packet and if the node keeps receiving data packets after that, a triggered RREP is waits book report only allowed to be sent once per questions, second. Table 3: Constants used in hachiko report the AODV implementation. Parameter Hello interval Active route timeout Route reply lifetime Allowed hello loss Request retries Time between retransmitted requests Time to hold packets awaiting routes Maximum rate for sending replies for questions nursing, a route Value 1,5 s 300 s 300 s 2 3 3s 8s 1/s 4.4.2 DSR The DSR implementation that came with the extension uses promiscuous mode (i.e. eavesdropping), which means that the protocol learns information from hachiko, packets that it overhears. The question is how realistic this is in a real environment. In a real case scenario we will probably have some sort of andreas dahmen, encryption, probably IP-Sec that uses IP-Sec tunneling to transport messages. We have made some small change to waits, DSR that makes it possible to jackson turner about, turn the hachiko book eavesdropping feature on and off. Good About Career Goals? The parameters that are configurable for DSR are shown in Table 4. These values are the values specified in hachiko book the DSR draft and have not been changed. The nonpropagating timeout is the time a node waits for a reply for compare, a nonpropagating search. A nonpropagating search is a request that first goes to the neighbors.
If the hachiko book neighbors do not answer in this specified amount of essay on flower, a time, a new request that will be forwarded by the neighbors will be sent. The sendbuffer in the DSR can hold 64 packets and the packets are allowed to stay in waits report the buffer for 30 seconds Table 4: Constants used in the DSR implementation. Parameter Time between retransmitted requests Size of source route header carrying n addresses Timeout for nonpropagating search Time to hold packets awaiting routes Maximum rate for sending replies for a route 33 Value 500 ms 4n + 4 bytes 30 ms 30 s 1/s 4.4.3 DSDV The extension also included an implementation of the DSDV protocol. This implementation is actually two implementations that handle the triggered update a little different. In the first version only a new metric for a destination causes a triggered update to be sent. In the second version, a new sequence number for a destination causes a triggered update to good essays career, be sent. Hachiko Waits? We have modified DSDV so it always uses the version that triggers on new sequence numbers. This is the version that, we feel behaves according to turner thesis frontier, the specification of DSDV. The parameters for waits book report, DSDV are shown in Table 5 and are as specified in the DSDV paper .
Table 5: Constants used in the DSDV implementation. Parameter Periodic route update interval Periodic updates missed before link declared broken Route advertisement aggregation time Maximum packets buffered per node per destination Value 15 s 3 1s 5 4.4.4 Flooding We have implemented a simple flooding protocol that simply floods all user data packets to all nodes in the network. To have some sort cleverness in this flooding and avoiding data to bounce back and forth we use a sequence number in each packet. This sequence number is incremented for each new packet. Each node keeps track of (source IP, sequence number) for all destinations and does not process a packet if the packet has a sequence number smaller than the compare film essay stored sequence number. The idea was to do the simulations on the flooding protocol and compare the results with the waits report results for dahmen, the routing protocols. Hachiko Waits? After some initial simulations on flooding this plan was abandoned. The simulations took too long to complete.
The reason is dahmen that flooding generates too many packets (events in the simulator). 4.4.5 The simulator To the actual simulator (ns + extension) we have added some new features to allow us to hachiko waits, make the wanted measurements. Obstacles The visualization/scenario generator tool, Ad-hockey, allows the user to place obstacles (lines and boxes) into the scenario. The problem is that ns do not use these obstacles for any kind of computation. Graduate? Two nodes can communicate, even through a wall. We wanted to simulate the protocols in a few realistic scenarios, so we added these computations to ns. The calculations consisted of two parts. The first part was to store all obstacles in a database that we later could use when calculating the hachiko waits report intersection points and the second part was to extend the propagation model with the dahmen actual computations. Waits Book Report? The computations merely consisted of deciding if there existed an intersection point between the straight line from the sending node to good about career, the receiving node and hachiko book report any obstacle in the database.
If such an intersection point exists, the communication is simply cut of. No fading of the signal, reflections etc is taken into career consideration. Waits Book? The model is therefore very simple. The problem with these computations is that it adds a lot of overhead in the simulations. The simulations will take significantly longer time to complete. The extra computation must be done for all packets. In a large scenario with many nodes that are sending a lot of traffic this will increase the jackson turner thesis simulation time significantly. Version management To allow us to test different versions of one protocol simultaneous, we have added a version control to ns. This means that it is possible to give a version number to a protocol when the simulation starts. This version number is given to the specified protocol and it is then up to the programmer to hachiko report, use it.
We currently use this feature with both AODV and on flower DSR. The different versions are: N N N N N AODV 1 = AODV with only hello messages. AODV 2 = AODV with only MAC-layer feedback. AODV 3 = AODV with both hello messages and book MAC-layer feedback. DSR 1 = DSR with eavesdropping. DSR 2 = DSR without eavesdropping. 34 5 Simulation study The protocols that we have simulated are DSDV, AODV and essay questions DSR. DSDV is only used to get a comparison of hachiko waits report, how much better/worse the MANET protocols are than an ordinary proactive protocol. The simulations were conducted on an Intel PC with a Pentium-2 processor at 400 MHz, 128 Mbytes of RAM running FreeBSD6. 5.1 Measurements Before we go into the actual simulations, we will discuss which parameters  that are interesting to greener essay, measure when studying routing protocols in hachiko waits book an ad-hoc network.
There are two main performance measures that are substantially affected by on flower garden the routing algorithm, the average end-to-end throughput (quantity of service) and hachiko report the average end-to-end delay (quality of service). 5.1.1 Quantitative metrics The measurements that we have conducted can be seen from two angels: externally and essay internally. Hachiko? The external view is compare and contrast essay what the hachiko waits book application/user sees and the internal view is how the good routing protocol behaves. The external measurements are basically the end-to-end throughput and delay. The internal behavior can further be divided into routing accuracy and routing efficiency. N N Routing Efficiency: How much of the sent data is actually delivered to the destination? How much routing overhead is required to find routes? Routing Accuracy: How accurate, measured in waits book number of hops are the supplied routes compared to the optimal shortest path.
5.1.2 Parameters The metrics has to be measured against some parameter that describes the andreas dahmen characteristic behavior of an adhoc network and hachiko can be varied in a controlled way. The parameters that we have chosen to simulate with are: N N N Mobility, which probably is compare and contrast film essay one of the most important characteristics of an ad-hoc network. This will affect the hachiko waits report dynamic topology, links will go up and down. Offered network load. The load that we actually offer the greener network. This can be characterized by waits three parameters: packet size, number of essay, connections and the rate that we are sending the packets with. Book? Network size (number of good essays about goals, nodes, the size of the area that the nodes are moving within). Hachiko Waits? The network size basically determines the connectivity. Essay Garden? Fewer nodes in the same area mean fewer neighbors to send requests to, but also smaller probability for collisions.
5.1.3 Mobility Because mobility is an important metric when evaluating ad-hoc networks we need some definition of mobility. Book Report? There exist many definitions of mobility. The American Frontier? The CMU Monarch project  has for instance used the pause time in hachiko waits book the waypoints as a definition of mobility. If a node has a low pause time, it will almost constantly be moving, which would mean a high mobility. Good? If a node has a large pause time it will stand still most of the time and have a low mobility. We did not think that this mobility definition was good enough, because even if the pause time is book low and all nodes are constantly moving, they could all be moving with a very slow speed in about goals the same area. We have defined mobility a little differently. Our definition is based on the relative movement of the nodes. Book? This definition gives a very good picture of how the nodes are moving relatively to each other. The definition is as follows: 6 FreeBSD 2.2.6 35 If several nodes move for place essay, a certain time, then the mobility is the average change in distance between all nodes over that period of waits report, time.
This time is the simulation time T. Dahmen Dissertation? Mobility is a function of hachiko book report, both the speed and the movement pattern. It is calculated with a certain sampling rate. During the simulations, we have used 0.1 seconds as sampling rate. This is the default time when logging the movement in the simulations, so it was appropriate to use the same value when calculating the mobility. Table 6 shows all variables that are used in the equations for the mobility factor. Table 6: Variable name dist(nx, ny)t n i Ax(t) Mx T t Mob Mobility variables.
Description the distance between node x and place essay node y at report, time t number of good essays about, nodes Index Average distance for node x to all other nodes at time t Average mobility for node x relative to all other nodes during the entire simulation time Simulation time Granularity, simulation step Mobility for entire scenario First of all, the average distance from each node to all other nodes has to be calculated. This has to be done at times t = 0, t = 0+X, t = 0+2X, . Hachiko Report? t = simulation time. For the node x at time t the essay on flower formula is: n ¦ dist (n , n ) x Ax(t) = i i1 (5.1) n 1 After that, with the use of hachiko report, (5.1), the average mobility for that particular node has to be calculated. This is the average change in distance during a whole simulation. The mobility for node x is: T t ¦ A (t ) A (t 't ) x Mx = x t0 (5.2) T 't Finally, the mobility for the whole scenario is the good essays about career sum of the mobility for all nodes (5.2) divided with the report number of nodes: n ¦M Mob = i i1 (5.3) n The unit for the mobility factor (5.3) is m/s.
The mobility factor therefore gives a picture of the average speed of the distance change between the nodes. Figure 11 shows some basic examples of how this mobility factor will reflect the actual movement. If the nodes are standing still, this will of course lead to a mobility of 0, but this would also be the case when the nodes relative movement is zero, for example when the film essay nodes are moving in parallel with the same speed. Waits Book? It is only when the essay nodes have a movement relative to each other that the waits book mobility factor will be greater than zero. Good Goals? 36 Our mobility definition reflects how the mobility affects the dynamic topology, without considering obstacles or surroundings. Standing still 0.0 Parallel movement 0.0 Figure 11: Relative movement 0.0 Example of mobility. The reason for choosing mobility as a parameter in the simulations is first of hachiko waits, all that the mobility is one of the most important characteristics of an ad-hoc network. But also because mobility is a parameter that is and contrast film easy to grasp for people in general. Hachiko Waits? Everyone has a rather good picture of what it means if the mobility is increased.
We have tested the essays about mobility factor to see how it affects the dynamic topology. As it can be seen in Figure 12, the number of hachiko waits, link changes is directly proportional to the mobility factor. A link change basically means that a link changes state from either up/down to down/up. The plot is the essay average values for all simulations that we have done using 50 nodes and an environment size of 1000x1000 meters. 3500 3000 Avg nr of link changes 2500 2000 1500 1000 500 0 0 0.5 Figure 12: 1 1.5 2 Mobility 2.5 3 3.5 Relation between the hachiko waits report number of link changes and frederick turner thesis mobility. 37 4 5.2 Simulation setup In this chapter we will describe how the simulations were done. We have done 4 different types of simulations: N N N N Mobility simulations: We vary the mobility to see how it affects the different metrics that we are measuring. Offered load simulations: We vary the load that we offer the network, to see how the protocols behave when for waits report, instance the load is high. Essays Career? Network size simulations: We vary the number of nodes in the network. Realistic simulations: A few realistic scenarios were designed.
These simulations do not give a general view of the protocol, but instead tests certain characteristics of the protocols. Because we had different versions of both AODV and DSR we decided to first compare the different versions of the same protocol. Hachiko? After that we did a more general comparison where we used one version of essay questions, each protocol and hachiko waits compared them against DSDV. Greener Place Essay? The comparisons made are therefore: N N N Comparison of AODV with only hello messages, AODV with only link layer support and ADOV with both hello messages and link layer support. Comparison of hachiko waits, DSR with and without eavesdropping. Comparison of essay, DSDV, AODV with both hello messages and link layer support and waits book DSR without eavesdropping. The reason for choosing DSR without eavesdropping in the last comparison, is essay as mentioned earlier that this is more realistic. Security features like encryption will prohibit eavesdropping in the future. The choice of AODV with both link layer support and hello messages was made because first of all, link layer support is probably a necessity to achieve a performance that is good enough and secondly because the removal of hello messages somewhat changes the overall functionality of AODV. Removal of waits report, hello messages would of course save us from the overhead of the hello messages, but also makes the protocol completely on-demand. Film Essay? A broken link could only be detected when a packet needs to hachiko, be sent on the link.
In all simulations, except the realistic scenario simulations, we have used a randomized scenario. The randomized scenarios have different parameters that affect the essay movement patterns. The parameters that can be changed are: N N N N N Maximum speed: Every time a speed is going to be randomized it is randomized in the interval [0,maximum speed]. Number of book, nodes: This was constant during the simulations. We used 50 nodes for all simulation except the size simulation where we varied the dissertation number of nodes.
Environment size: Determines the size of the environment. We have used a size of 1000 x 1000 meters for all simulations except the realistic simulations where we have used 1500 x 900. Simulation time: The time for waits, which the simulations will be run at. We have used a simulation time of 250 seconds for all simulations except the realistic simulations where we used 900 seconds. Pause time: Pause time is the time for which a node stands still before randomizing a new destination and the speed that will be used to reach this destination.
We have used a pause time for 1 second in all simulations. The randomizing of scenarios works like this: first of all every node stands still for pause time seconds. After that each node selects a random destination, a waypoint somewhere in the environment space. Each node also randomizes a speed that will be used when moving to the waypoint. This speed is randomized uniformly in the interval 0 to greener, maximum speed. Every time a node reaches a waypoint, this procedure will be repeated. A factor that we have not taken into consideration with the scenarios is the fact that a real person is not likely to stand on the same place if the connection goes down. A real person is more likely to find a place where the reception is good enough. The system would be to hachiko book, complex if this factor were included also. We have assumed bi-directional links during all our simulations, i.e. the links work equally well in both directions.
It is questionable if unidirectional links are desirable when using the IEEE 802.11 MAC protocol, because bi-directional links are necessary if 802.11 acknowledgements are supposed to be used. 38 5.3 Mobility simulations 5.3.1 Setup The simulations where we varied the essay mobility where done by randomizing scenario files. This method is very hard to perform, because we cannot prior a scenario generation say that we want a mobility factor of exactly X. Instead we used the maximum speed parameter to control the scenario. The simulation parameters that have been used for the mobility simulations are shown in Table 7. Table 7: Parameters used during mobility simulations. Parameter Transmitter range Bandwidth Simulation time Number of hachiko book report, nodes Pause time Environment size Traffic type Packet rate Packet size Number of flows Value 250 m 2 Mbit 250 s 50 1s 1000x1000 m Constant Bit Rate 5 packets/s 64 byte 15 The scenario is nursing a very crucial part of the simulation. We have therefore collected 10 measurements for hachiko book report, each wanted mobility factor. The mobility factors that we simulated on are: 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5.
Because of the hard part of getting scenarios that are precise we have used an essay interval of r0.1 for the above mentioned mobility factors. The scenarios that where created where then analyzed in terms of unreachable hosts. Hachiko Book? We did not want to dissertation, investigate network partition at this stage, so all scenarios with extremely high degree of unreachable hosts where discarded. Hachiko Waits Book? By increasing the maximum speed in the scenario generation, the mobility will also increase. A mobility factor of 3.5 approximately corresponds to a maximum speed of 20 m/s. For the frederick thesis frontier randomized simulations we have varied the maximum speed in the interval 0 to 20 m/s. A speed of 20 m/s corresponds the speed of hachiko waits book report, a vehicle, which will lead to a high mobility. We used the same communication pattern for all mobility simulations. The traffic pattern consisted of 15 CBR sources that started at different times. Essay On Flower Garden? We did not use TCP for the simulations, because we did not want to investigate TCP, which uses flow control, retransmit features and so on. We wanted to get a general view of how the routing protocol behaves.
The communication pattern was randomly created. The parameters that was specified when randomizing the communication pattern were the number of wanted sources, the packet size, the rate at which they were sending and the simulation time. Hachiko Book Report? In these simulations, we wanted to essay garden, investigate how the mobility affected the protocols, so the hachiko report load that we offer is essay very low. We only use 15 CBR sources sending 64 bytes large packets with a rate of 5 packets/s. The bandwidth of the links are 2 Mbit. 39 5.3.2 Fraction of received packets 0.8 Fraction received packets 1 0.8 Fraction received packets 1 0.6 0.4 0.2 0.6 0.4 0.2 AODV-HELLO-MAC AODV-MAC AODV-HELLO DSR-eaves dropping DSR 0 0 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 1 Fraction received packets 0.8 0.6 0.4 0.2 AODV-HELLO-MAC DSR DSDV 0 0 0.5 1 1.5 2 Mobility (m/s) Figure 13: 2.5 3 3.5 Mobility simulations - fraction of received packets. Waits Report? How many of the sent data packets are actually received and why have the dropped packets been dropped?
Of the different AODV versions, it can been seen in andreas dissertation Figure 13 that both AODV versions that have MAClayer support are almost receiving all packets that are sent. AODV with both hello messages and MAC-layer support is hachiko waits slightly better than the version with only MAC-layer support. The reason for good about, this is the same as mentioned earlier, the hello messages gets some prior knowledge of link breakages. AODV with only hachiko report, hello messages is however dropping a very large portion of the packets when the mobility increases. This large fraction of dropped packets is dahmen dissertation of course not acceptable and the reason for these drops has to hachiko, do with the interval of the on flower garden hello messages. The interval between the hello messages and the number of hachiko report, allowed hello message losses are crucial for detection of link breakages. If the interval is essay on flower decreased, link breakages are detected earlier, but it would also mean that the control overhead in the network increases. The issue here is to waits, try to find optimal values for these parameters. The choice of these parameters is also very dependent on essays career, the behavior that is desired; a higher fraction of received packets, a high throughput, low delay or a low overhead. The fraction of received packets for hachiko book, the DSR versions is very large even for film, high mobility.
The DSR version without eavesdropping has a slightly smaller fraction of received packets. This difference is however so small that it is waits book negligible. DSR with eavesdropping gets better result for the simple reason that it has a little more information when calculating the routes. Andreas Dahmen Dissertation? A reason for the higher fraction received packets for DSR compared to AODV is that DSR allows packets to stay in the send buffer for as long as 30 seconds, AODV only 8 seconds (our implementation). It must however be noted that the AODV draft  does not specify how long a packet is allowed to stay in the sendbuffer. When comparing these results with the results for DSDV it can clearly be seen that a proactive approach is not acceptable at all when the mobility increases. Waits Book Report? The fraction received packets drastically goes down to 56-57 %. Essay Nursing? This value is however for a very large mobility factor (vehicles).
But the hachiko waits book fraction of received packets is not even 100 % when the mobility is 0, as for all other protocols. The reason for this is that packets are sent before the greener place essay routing tables have had enough time to report, converge and the packets are dropped. Graduate Essay Questions? 40 The main reasons for dropping packets are that the protocol is sending packets on a broken route that it thinks is valid and that packet in the buffers are dropped because of congestion and timeouts. Waits Book Report? At this low load we only have a small fraction of the packets that have been dropped because of essay, collision. Hachiko? It can also be seen that IP-based hello messages as only compare and contrast film essay, link breakage detection mechanism is not a good idea. The results are very poor, even DSDV have slightly better results. Link layer feedback of hachiko waits book report, link breakages informs the upper layer routing protocol is compare essay much quicker and it can therefore react immediately. 5.3.3 End-to-end delay AODV-HELLO-MAC AODV-MAC AODV-HELLO 0.14 0.12 Avg packet delay (seconds) 0.12 Avg packet delay (seconds) DSR-eaves dropping DSR 0.14 0.1 0.08 0.06 0.1 0.08 0.06 0.04 0.04 0.02 0.02 0 0 0 0.5 1 1.5 2 2.5 3 3.5 2.5 3 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 3.5 Mobility (m/s) AODV-HELLO-MAC DSR DSDV 0.14 Avg packet delay (seconds) 0.12 0.1 0.08 0.06 0.04 0.02 0 0 0.5 1 1.5 2 Mobility (m/s) Figure 14: Mobility simulations - delay. Waits Book Report? As seen in Figure 14, of the different AODV versions AODV with only hello messages has lowest delay on the data packets that are received. The reason for this is graduate essay not that it finds routes faster or that the routes are shorter or more optimal, instead AODV with only hello messages is the AODV version that gets significantly fewest packets through the network. The packets that it successfully gets through the network have approximately the same low delay as for the other AODV versions.
The difference is that the other AODV versions have a portion of packets that have a higher delay (has been in a buffer a long time and book still gets the packets through the essay on flower garden network). This affects the average delay, which becomes larger. In AODV with only hachiko waits book report, hello messages, packets in the buffers that have been there for a long time are dropped. Andreas Dissertation? The reason is that ADOV does not successfully find a new route for waits, those packets and because broken links are not detected fast enough, resulting in that a source can keep sending packets on a broken link believing that it is still working properly. Good About Career Goals? AODV with both hello messages and MAC layer support has a slightly lower delay than AODV with only MAC-layer support. The reason for this is that as mentioned earlier, AODV with only MAC-layer support makes the protocol completely on-demand, it only detects link breakages when actually trying to send packets. Packets that are sent after this breakage is detected will have a higher delay, because they are buffered during the time it takes to find a new route.
AODV with both hello messages and Mac-layer support on the other hand will get some prior knowledge of the link breakage and has a chance to find a new route before any new packets are sent. 41 Both DSR versions show a tendency to get higher delay when mobility is increased. The turning point comes at waits, a mobility factor of approximately 1.0. DSR without eavesdropping has a negligible higher delay compared to DSR with eavesdropping. DSDV is the protocol that seems to have lowest delay in these results. The results are however somewhat misleading because DSDV drops so many packets that it cannot said to be valid. The packets that are dropped in DSDV will successfully get through when using for instance DSR, but has a slightly higher delay, because of longer times in on flower garden buffers etc.
These higher delay packets will make the average delay higher for DSR. Hachiko? The same can be said for greener, AODV with only waits book report, hello messages. Essay Questions? The other two AODV versions have a slightly higher delay than the DSR versions. This has probably to waits, do with the source routing concept of DSR. Essay Questions Nursing? DSR gains so much information by the source routes that it will learn routes to many more destinations than a distance vector protocol like AODV.
This will mean that while DSR already has a route for a certain destination, AODV would have to send a specific request for that destination. The packets would in the meanwhile stay in a buffer until a valid route is found. This will take some time and report will therefore increase the average delay. In a packet based radio network without Quality of Service, the essays about goals delays of the packets will vary much. The packets that do not have a route will be buffered until a route is found. A critical parameter here is how long a packet should be allowed to stay in the buffer before it is thrown away. If the packets are allowed to be in the buffer for a long time, the following situation could happen: A packet is hachiko report sent, but there does not exist any route to that destination so the good about career goals packet is buffered and report a route request is sent. The destination node is on flower however unreachable so no route reply is hachiko waits book returned to the sending node.
After a long time, the destination node suddenly becomes reachable and the packet is sent. This packet will have a very large delay. Place? Should this situation be allowed to happen? Should the packet be dropped from the buffer at hachiko waits, a much earlier stage or do we want all packets to get through the greener place essay network, even though the hachiko waits book delay can be very large. In the compare case where we are using TCP, the waits retransmit operation will probably retransmit the packet at an earlier stage anyway, because no acknowledgement was received.
The allowed time for packets to stay in essay the sendbuffer in DSR is waits report 30 seconds and only 8 seconds for AODV. If a packet is dahmen received 30 seconds after it was sent, this will increase the average delay to some degree. 5.3.4 End-to-end throughput 2.4 2.2 2.2 Throughput (Kbit/s) 2.6 2.4 Throughput (Kbit/s) 2.6 2 1.8 1.6 1.4 2 1.8 1.6 1.4 1.2 1.2 AODV-HELLO-MAC AODV-MAC AODV-HELLO DSR-eaves dropping DSR 1 1 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 0 0.5 1 1.5 Mobility (m/s) 2.6 2.4 Throughput (Kbit/s) 2.2 2 1.8 1.6 1.4 1.2 AODV-HELLO-MAC DSR DSDV 1 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Figure 15: Mobility simulations - throughput. 42 2 2.5 3 3.5 Figure 15 shows the throughput curves for book report, the different protocols with a packet size of 64 bytes. It must however be mentioned that the curves in and contrast film this case are only interesting from a relative view, as a comparison between the protocols. We have not tried to maximize the throughput, we have only tried to determine the relative difference in book throughput for the different protocols with respect to the mobility factor and greener the specific load that we have used. The throughput curves for all protocols are very similar to the fraction received packet curves. This is logical because large packet drops will of course mean lower throughput. Both DSR versions and the AODV versions with link layer support have almost identical throughput. This throughput is also approximately constant, it decreases somewhat when mobility is as high as 2.5-3.5. AODV with only hello messages and waits book report DSDV have a throughput that drastically decreases when mobility increases.
AODV with only hello show a very poor result. The throughput curve drops almost immediately to half of what it is when mobility is 0. 5.3.5 Overhead 25000 1.8e+06 AODV-HELLO-MAC AODV-MAC AODV-HELLO 20000 1.4e+06 Control overhead (bytes) Control overhead (packets) AODV-HELLO-MAC AODV-MAC AODV-HELLO 1.6e+06 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 0 25000 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1.5 2.5 3 3.5 2.5 3 3.5 1.8e+06 DSR-eaves dropping DSR DSR-eaves dropping DSR 1.6e+06 1.4e+06 Control overhead (bytes) Control overhead (packets) 20000 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 Mobility (m/s) 25000 1.8e+06 AODV-HELLO-MAC DSR DSDV AODV-HELLO-MAC DSR DSDV 1.6e+06 20000 1.4e+06 Control overhead (bytes) Control overhead (packets) 2 Mobility (m/s) 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 Figure 16: 3 3.5 0 0.5 1 1.5 2 Mobility (m/s) Mobility simulations - overhead. Because the essay routing protocol need to send control information to achieve the task of hachiko book, finding routes, it is interesting to essay, see how much control information that is actually sent for hachiko report, each protocol. There exists some sort of tradeoff between the byte overhead and the number of control information packets sent. A large byte 43 overhead would of essay on flower garden, course mean a larger part of wasted bandwidth. Many small control information packets would however mean that the hachiko book radio medium on which packets are sent is acquired more frequently. This can be quite costly in terms of greener essay, power and book network utilization. Essay On Flower Garden? The values that we have plotted do not include any physical layer framing or MAC layer overhead. We have only hachiko waits, looked at the overhead at the IP-level. A completely fair comparison would also include the dahmen dissertation above mentioned overheads. We have chosen not to include these for the simple reason that the MAC layer can be different in a real life implementation.
We wanted to investigate the overhead generally, not the overhead that is waits dependent on compare film essay, particularly the IEEE 802.11 MAC protocol. The results are shown in Figure 16. The first column is overhead calculated in number of packets and the second column is the byte overhead. The number of control packets and byte overhead is a total for all simulations done where we have varied mobility. Of the different AODV versions, it can be seen that the waits curves for the AODV versions that have link layer support are similar in appearance. Compare Film? The difference of about 8000-9000 packets and 270000-290000 bytes that can be seen corresponds to the hello packets. The AODV version with only hello messages has a much more stable form of the curve. The small rise that is visible is the triggered route replies that are sent when a link goes down and the new requests that are sent to find a new route during route failures.
A route failure therefore triggers both triggered replies and new requests. This rise is much larger for the AODV versions with link layer support for hachiko waits report, the simple reason that it detects link failure much faster, which will lead to much more messages. DSR does not include the data packets in the number of control packet calculations, only the extra byte overhead from these packets is included. Worth noting when observing the DSR versions is that the DSR version that does not use eavesdropping has approximately the double amount of control overhead counted in greener essay number of report, messages and about 400000 bytes more of byte overhead than the DSR version with eavesdropping at the highest mobility 3.5. The somewhat strange behavior of the byte overhead for DSR can be explained as a sum of both the sent packets and the sent control messages.
As mobility increases, fewer packets will get through the andreas network. Hachiko Waits? Fewer packets mean less byte overhead in the source route of the graduate packets. Increased mobility also means more topology changes, which will increase the number of update messages. Hachiko Book? The byte overhead is therefore decreasing and at approximately mobility 1.5 the increase of control messages will cause the byte overhead to good, increase. The number of control messages in DSDV is fairly constant, even when the mobility is extremely high. This is the nature of a proactive protocol that is dependent on periodic broadcasts. The byte overhead on the other hand, will increase as mobility increases. The reason for this is that the amount of information sent in hachiko report each update message will be larger as the amount of link changes increases. 5.3.6 Optimal path One internal aspect of the routing protocol is the routing accuracy, e.g. how good the greener place actual routes are compared to the optimal routes. To illustrate this we have compared the actual hop count with the optimal shortest route for all received packets. We have then, for each protocol, calculated how large fraction the hachiko waits book received packets that have been routed through the optimal route, a route with hopcount that is one larger than the optimal, a route with hopcount that is film two larger than the optimal and so on.
The result is hachiko waits book report shown in Table 8. The results are the frederick thesis about total results for all simulations done with varying mobility. To better illustrate the waits book report difference between some of the protocols, we have also plotted the turner thesis about the american results for hachiko waits, one AODV version, one DSR version and compared it with the only proactive protocol DSDV. It can clearly be seen in greener place Figure 17 that DSDV is the protocol that has the highest degree of optimality, almost 90 % of the received packets have been routed with optimal hop count. The AODV and hachiko waits DSR versions are almost identical. AODV is slightly better. Film? This difference is waits report however so small that it can neglected. The difference between the different DSR versions is andreas dahmen quite large and can be explained with the waits book extra information that DSR with eavesdropping has when calculating routes. This extra information is apparently very informative when calculating shortest possible routes. AODV with only hello messages has best results of the different AODV versions. These due to essay, the similarities with a proactive protocol like DSDV that is highly dependent on periodic broadcasts.
Because of the periodic updates DSDV needs some time before it converges to a steady state. This happens when we have high movement with a lot of topology changes. Most of the packets that are sent during this time are dropped and the rest of them get a little higher hopcount. All packets that are sent after the routing tables have converged to a steady state do however most likely have the optimal shortest path. AODV with only hello messages have a similar behavior. Waits Report? Link breakages are dependent on the hello messages. This will mean that high movement and frequent topology changes will lead to many packet 44 drops during this time.
The packet that successfully gets through the network have done this during times when the network is on flower garden somewhat stabile 1 AODV-HELLO-MAC DSR DSDV Packets (%) 0.8 0.6 0.4 0.2 0 0 2 Figure 17: 4 6 Nr of hops from optimal 8 10 Mobility simulations - optimal path difference. Because both DSR versions and the AODV versions with link layer support gets significantly more packets through the network when the number of topology changes is hachiko large, they will have a little lower fraction of good career goals, packets that have a optimal route. In times of frequent movement it is waits easy to get a route that at first is graduate nursing optimal and hachiko book then the moment later is dissertation 1-2 hops longer than another route that become the optimal route. The protocols will keep sending packets on report, the route that at first was optimal. A good relative comparison is to look at the average hop count difference for all packets received. DSDV has the smallest average with a hopcount at only 0.13 hops from the optimal path. Table 8: Protocol AODV 1 AODV 2 AODV 3 DSR 1 DSR 2 DSDV 0 79.1% 55.9% 68.4% 81.1% 63.2% 88.7% Optimal path difference for frederick jackson turner thesis about the american, all protocols.
Number of hops from optimal path (% packets) 1 2 3 4 5 6 14.8% 3.68% 1.08% 0.30% 0.55% 0.06% 29.9% 9.04% 2.62% 1.09% 0.56% 0.20% 23.0% 5.37% 1.48% 0.84% 0.47% 0.14% 15.3% 2.73% 0.54% 0.13% 0.08% 0.01% 26.6% 7.21% 2.21% 0.56% 0.13% 0.05% 10.6% 0.59% 0.06% 0.00% 0.00% 0.00% 45 7 0.06% 0.38% 0.04% 0.02% 0.03% 0.00% Average 0.292170 0.682837 0.459423 0.234429 0.512004 0.126577 5.3.7 Summary mobility simulations The protocols that have link layer support for link breakage detection will be much more stable. The fraction of packets received for these protocols is almost constant at 95 % even when mobility increases. Hachiko Report? This result indicates that these kinds of protocols will get the andreas dahmen job done even when mobility increases. These protocols include both DSR versions and hachiko report the two AODV versions that have this link layer support. Protocols that are highly dependent on essay, periodic broadcast show a rather poor result, only little more than 50 % of the packet are received when mobility is increased. Because DSR is a source routing protocol it is always interesting to see how much overhead this kind of protocol will have. The byte overhead is larger than for instance the AODV version that uses both hello messages and link layer support for waits book, link breakage detection. Jackson Turner Thesis? The interesting thing with this is that the number of control messages is much smaller for DSR than any other protocol. Book? This is interesting because this means that an approach that uses a source routing based approach to find routes combined with a destination vector approach for sending data packets could be desirable. Andreas Dahmen Dissertation? 5.4 Offered load simulations We have used these protocols for waits book report, these simulations: N N N AODV with both hello messages and frederick turner thesis about MAC link layer support. Waits Report? DSR without eavesdropping DSDV We only used the more realistic version of both AODV and DSR, for the same reason as mentioned in the previous section.
5.4.1 Setup The offered load simulations where done by varying the andreas load that we offer the network. We had mainly three parameters to adjust the offered load: N N N Packet size Number of report, CBR flows Rate at which the flows are sending The mobility simulations that we have done used a packet size of 64 bytes, a rate of 5 packets/s and frederick thesis about the american 15 CBR flows. This is a fairly moderate offered load, so for the offered load simulations, we wanted to investigate how the protocols behave when the load was increased. We could increase the packet size or the number of CBR flows, but the book report parameter that best describes the load is the rate at which we are sending. By only increasing the rate for the CBR flows, the essay questions load for hachiko waits report, each flow will increase. This also gives some hints of how large the throughput can be. Place? We have used four different offered load cases: N N N N 5 packets / second (same as the mobility simulations) 10 packets / second 15 packets / second 20 packets / second The packet size was held constant at 64 bytes and the number of flows at 15.
We used the same randomized scenario files as in the mobility simulations. The same communication file was also used, with the exception that we changed the rate for the CBR sources. The parameters that we used during the offered load simulation are shown in Table 9. 46 Table 9: Parameters used during offered load simulations. Hachiko? Parameter Transmitter range Bandwidth Simulation time Number of nodes Pause time Environment size Traffic type Packet rate Packet size Number of flows Value 250 m 2 Mbit 250 s 50 1s 1000x1000 m Constant Bit Rate 5 packets/s 64 byte 15 5.4.2 Fraction of received packets 0.8 Fraction received packets 1 0.8 Fraction received packets 1 0.6 0.4 0.2 0.6 0.4 0.2 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1 Fraction received packets 0.8 0.6 0.4 0.2 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 0 0 0.5 Figure 18: Offered load simulations - fraction of received packets. At only greener place essay, 5 packets/s both AODV and DSR are rather constant, the fraction of waits book, received packets is only decreasing slightly when mobility increases (Figure 18). At 10 packet/s we can see that the fraction received packets is decreasing much faster when the mobility factor is greater than 2. At 15 packets/s and 20 packets/s both AODV and DSR are dropping a large fraction of the packets. At the highest mobility and a rate of 20 packets/s, only 50-60 % of the andreas dahmen dissertation sent packets are received. The reason is more collisions in the air and hachiko report congestion in compare buffers.
The results for AODV and DSR are fairly similar at a packet rate of 5 packets/s and 10 packets/s. At data rates of 15 packets/s and 20 packets/s, AODV shows a better result than DSR. At these rates the protocols are however dropping a large fraction of the packets, even at book report, a mobility factor of 0. DSR will have a much larger byte overhead than AODV at higher data rates (Figure 21). The reason for this is the source route in each data packet. This also increases the load on film essay, the network and causes more packets to be dropped; thus AODV will get more packets through the network.
47 DSDV is dropping a large fraction of the packets already at the lowest data rate 5 packets/s. Hachiko Book Report? It must however be noted that the increase in dropped packets is not as large for DSDV as for AODV and DSR. At the highest data rate, DSDV is almost as good as DSR. Essay? 5.4.3 End-to-end delay 0.7 0.7 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 0.6 0.5 Avg packet delay (seconds) Avg packet delay (seconds) 0.6 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 0.4 0.3 0.5 0.4 0.3 0.2 0.2 0.1 0.1 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Mobility (m/s) 0.7 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s Avg packet delay (seconds) 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Figure 19: Offered load simulations - average delay. The delay is also affected by hachiko report high rate of CBR packets (Figure 19). The buffers becomes full much quicker, so the packets have to stay in the buffers a much longer period of greener place essay, time before they are sent. This can clearly be seen at the highest rate 20 packets/s. The high degree of packet drops, even at mobility 0 makes the delay high already from the start.
DSR has a much lower delay compared to AODV. The difference between AODV and DSR is most apparent at rate 10 packets/s. DSDV has the lowest delay of them all. This is however an effect from the large fraction of book report, packet drops that DSDV has, compared to DSR and AODV. The increase in turner thesis about the american frontier delay for DSDV also comes from the increased time that the packets must stay in the buffers. The high delay at report, a mobility factor of 0-1 and a data rate of 20 packets/s that can be seen for all protocols is a result of the extremely high data rate and and contrast film essay the low mobility. The high data rate will fill up the hachiko book buffers very quickly. The low mobility will mean that already found routes are valid for a much longer time period. This means that found routes can be used for more packets.
Even the packets that have stayed in the buffer for a long time have a chance to get through. When mobility increases, more routes will become invalid and new requests are necessary. While the requests are propagating the garden network in search for a new route, buffers will get full and packets are dropped. These packets are the packets that have stayed in the buffers for the longest time and therefore the delay will decrease. The increase in mobility actually results in a load balancing of the traffic between the nodes; hot spots are “removed” due to hachiko book report, mobility. For DSDV, the average delay at highest data rate will actually be lower than at the rate of 15 packets/s. This is a little strange but has probably something to do with the fact that DSDV only uses a buffer that only has room for frederick turner thesis about frontier, 5 packets per hachiko waits book report, flow.
At the rate of 15 packets/s and 20 packets/s, when mobility starts to get so high that the topology changes frequently, only greener place, 40-60 % of the packets gets through the network. These 48 topology changes means that the hachiko waits book report protocol needs more time to converge before the packets can be sent. Thesis The American Frontier? The buffers will therefore be congested almost all the time so the packets that actually get through have approximately the hachiko book report same the delay. Film Essay? 5.4.4 End-to-end throughput 8 8 6 Throughput (Kbit/s) 7 6 Throughput (Kbit/s) 7 5 4 3 5 4 3 2 2 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 1 0 0 0 0.5 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 1 1 1.5 2 Mobility (m/s) 2.5 1.5 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 8 7 Throughput (Kbit/s) 6 5 4 3 2 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 1 0 0 0.5 1 2 3 3.5 Mobility (m/s) Figure 20: Offered load simulations - average throughput. At low CBR rates the throughput of hachiko book report, DSR and AODV is unaffected of the mobility (Figure 20), it stays constant at 2,5 Kbit/s. At higher CBR rates, the throughput will decrease when the mobility increases. This can already be seen at CBR rate 10 packet/s.
The decrease at CBR rate 10 packets/s is however very small. At rate 15 packets/s and andreas dahmen dissertation 20 packets/s the hachiko book throughput decreases very much for all protocols. This is however an effect from the large fraction of film, dropped packets. The result for AODV is hachiko waits slightly better than for DSR. It must however be noted that the jackson turner the american offered load definition that we use only includes the rate at hachiko waits report, which we are sending packets with; no control packets are included in this definition. The same applies for graduate nursing, the throughput, only the data packets are included in the calculations of throughput. DSR have a much larger byte overhead than AODV at higher data rates (Figure 21). Hachiko Waits Report? This also increases the load on the network and causes more packets to be dropped; thus AODV will have a better throughput at higher data rate.
DSDV drops a large fraction of the packets already at a rate of 5 packets/s. This can be seen in the small decrease in the throughput at essays career, rate 5 packets/s. The throughput decreases more and more as the report rate increases. 5.4.5 Overhead In Figure 21, the difference between distance vector and source routing can clearly be seen. Jackson Thesis The American Frontier? The byte overhead for DSR is much larger than AODV even at hachiko waits book report, low data rates and the difference becomes larger when the CBR rate increases. At CBR rate 20 packets/s, the byte overhead for DSR is more than the double than for AODV. The reason for graduate nursing, the larger byte overhead for DSR is of course the waits book source route in garden each packet. Hachiko Waits Book? The 49 number of control messages is though smaller for jackson frontier, DSR. This is the hachiko other characteristic for andreas dissertation, source routing, it learns all routes in the source route and therefore does not need to send as many route requests. The reason for the increase in number of hachiko book, control packets is the compare film MAC-layer support. The increase in rate means that the MAC-layer will detects link failures much faster.
This means that the triggered RREPs are sent much earlier also causing the source node to send out hachiko a new request much earlier. All link failures are detected earlier with increased rate; thus there will be time for more RREQs, RREPs and questions nursing triggered RREPs. 4e+06 35000 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 30000 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 3.5e+06 3e+06 Control overhead (bytes) Control overhead (packets) 25000 20000 15000 10000 2.5e+06 2e+06 1.5e+06 1e+06 5000 500000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 0 3.5 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 35000 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 30000 4e+06 3e+06 Control overhead (bytes) 25000 Control overhead (packets) DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 3.5e+06 20000 15000 2.5e+06 2e+06 1.5e+06 10000 1e+06 5000 500000 0 0 0.5 1 1.5 2 2.5 3 0 3.5 0 0.5 1 Mobility (m/s) 1.5 2 2.5 3 3.5 Mobility (m/s) 4e+06 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 35000 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 30000 3.5e+06 3e+06 Control overhead (bytes) Control overhead (packets) 25000 20000 15000 10000 2.5e+06 2e+06 1.5e+06 1e+06 5000 500000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 Figure 21: 3 0 3.5 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Offered load simulations - overhead. The amount of control information in DSDV is not affected to any great extent by the data rate for the CBR packets. By looking at Figure 21 it looks like the number of control packets is exactly the same for hachiko waits, all data rates, but there is graduate essay questions actually a small difference. The number of control packets is actually a little smaller when the rate is 20 packets/s. This difference is about 80 packets.
The reason for this difference is that the high data rate causes more collisions, which means that some of the update messages are dropped. Hachiko Waits Report? These lost update messages will not be received by any node, and cannot therefore trigger new update messages. This means that when the next update message actually is received a much larger update message has to be sent, thus we can see a slight increase of byte overhead when the rate increases. But when the graduate mobility increases more and more packets will be dropped. At the highest data rate, many of the update messages are dropped, 50 even the packets with a little more information. This causes the byte overhead for DSDV at higher data rates not to report, increase to the same extent as for DSDV with lower data rates. 5.4.6 Optimal path Figure 22 illustrates the difference in hopcount from the optimal hopcount at a CBR rate of 20 packets/s. It is the result for all simulations done at this rate. If we compare this figure with Figure 17, which illustrates the hopcount difference for andreas dahmen dissertation, the CBR rate 5 packets/s, we can clearly see that they are almost identical.
The rate does not affect the number of hops that the packets actually need to travel from source to destination. 1 AODV 20 pkt/s DSR 20 pkt/s DSDV 20 pkt/s Packets (%) 0.8 0.6 0.4 0.2 0 0 2 Figure 22: 4 6 Nr of hops from optimal 8 10 Offered load simulations – optimal path. 5.4.7 Summary offered load simulations The performance of the protocols differs slightly during different network loads. Hachiko Waits Report? The most apparent difference is the byte overhead. While DSDV has a rather unaffected overhead, it increases both for AODV and DSR during higher loads.
A higher sending rate causes the protocol to detect broken links faster, thus reacting faster. This leads to on flower garden, a slight increase in waits control packets, which also affects the film essay byte overhead. Hachiko Waits? The most apparent is the increase in DSRs overhead as we increase the essay garden send rate. Since each data packet contains a source route, the book byte overhead increases dramatically. The increased send rate also set demands on the send buffer of the routing protocol.
Congestion occurs and packets are dropped. The faster a routing protocol can find a route, the less time the packets have to spend in buffers, meaning a smaller probability of packet drops. 51 5.5 Network size simulations We did simulations on some of the protocols and dahmen dissertation varied the number of nodes that participated in the network. Hachiko Waits Book? We decreased the number of nodes to 35 and 25 nodes. Place? The decrease in number of nodes basically meant that the connectivity also decreased; each node had fewer neighbors.
The results from waits book report, these simulations did not give any new information regarding the performance of the protocols. The relative difference between the protocols was the same. Decreased connectivity meant of course that we did not get as many packets through the network as in the mobility simulations, but it must however be noted that the dependency between the scenarios and results are much larger in the network size simulations. The worst results for each protocol happened when the graduate mobility was 0. This may sound strange, but the reason for the bad result when the nodes is standing still is the randomized scenarios. If a randomized scenario has poor connectivity, this connectivity will be same during the whole simulation if the nodes are standing still. The nodes are not moving and cannot therefore affect the connectivity. Hachiko Book? In a scenario with moving nodes however, the connectivity will vary during the whole simulation. So even if a node is unreachable from the beginning, there is still a chance that it will be reachable some time later. 5.6 Realistic scenarios 5.6.1 Setup The randomized simulations we have done, gives a very good general picture of how the protocols behaves in respect to certain parameters, such as mobility, size and network load. This kind of simulations also has some problems: N N N It is hard to identify situations in essay which the protocols fail or have problems It has no connection to report, a real life situation. About? It may favor complex protocols, while in real life scenarios simpler protocols can find the routes almost as effectively.
It is therefore also very interesting to see how the protocols behave in a more realistic scenario. We have therefore done simulations on some scenarios believed to be realistic. The realistic scenarios do not give a full picture of hachiko report, how the protocols behave generally. Instead they give some sense of weak points in the protocols. The three basic types of frederick, scenarios that we have done simulations on book report, are: N N N Conference type, with low movement factor.
Event coverage type, with fairly large movement factor. Could for instance be reporters trying to interview politicians. Disaster area, with some relatively slow nodes and some very fast nodes (mounted on a car or a helicopter). Greener Place Essay? The environment size is 1500 x 900 meters for all realistic scenarios. This size is scaled according to the range of the transmitters. In a real life conference scenario, the environment size would be significantly smaller and so would also the transmitter range.
The same thing would apply for the speed of the book report people moving around. The speed is also scaled to about goals, 10 m/s. Hachiko Book Report? All parameters used during the compare film realistic simulations are shown in Table 10. Book Report? 52 Table 10: Parameters used during realistic simulations. Career Goals? Parameter Transmitter range Bandwidth Simulation time Number of nodes Environment size Traffic type Packet rate Packet size Speed of a human Speed of a mobile node mounted on a vehicle Value 250 m 2 Mbit 900 s 50 1500x900 m Constant Bit Rate 4 packets/s 512 byte 1 m/s 20 m/s 5.6.2 Conference This scenario simulates 50 people that are attending a conference, seminar session or some similar activity. It involves communication between some of the people. Parameters specific for the conference scenario are shown in Table 11 Table 11: Parameters used during conference scenario.
Parameter Number of CBR sources Number of hachiko waits book, receivers Number of essay, flows Value 2 6 6 The scenario is characterized by: N N N N N Low mobility factor, 10 % of the nodes are moving during any period of time. Links are long lasting and involves many hops. Book? The traffic is concentrated to a few nodes, typically only the speaker. Compare And Contrast Essay? Few obstacles which are far apart. Typically only one large obstacle, a wall with doors and waits book report windows that can be used for communication. Relatively large interference from frederick jackson about, other nodes, due to the concentration of transmitting nodes. This can in some cases lead to local congestion. The scenario basically tests the protocols: N N N Ability to respond to local changes for long links. Ability to waits report, cope with large concentration of traffic.
Message overhead with low mobility factor. Figure 23 shows how the scenario was designed and created with ad-hockey. The scenario is graduate essay questions nursing divided into waits book report three zones that have their certain characteristics. N N N Zone 1 - Speaker zone: The speaker moves back and forth. Compare Essay? This changes the closest neighbor in the audience.
Zone 2 - Audience zone: Static audience that is sitting still most of the hachiko waits book time. Very seldom does a node go outside to return a certain amount of time later. This will probably result in a link breakage of a longlasting link. Zone 3 - Outsider zone: Outsiders behind a wall that are trying to establish a connection between the frederick turner thesis about speaker and each other. 53 Transmitter range Zone 1 Zone 2 Zone 3 = Node = Obstacle = Movement Figure 23: Conference scenario. Hachiko Waits Book? The results for this scenario are shown in andreas dahmen Table 12 and Table 13.
It must however be noted that we do not distinguish the hachiko report results for nodes that are in zone 2 or zone 3. Questions Nursing? The calculated mobility factor for this scenario is very low. All protocols except DSDV and the AODV version that only uses hello messages show quite good performance, delivering between 92-99% of the packets with an average throughput between 14.8 – 15.7 Kbit/s. Hachiko Waits Book? DSDV delivers only jackson turner the american, 75.6% of the packets with an average throughput of 12.1 Kbit/s and hachiko book the AODV version with only hello messages delivers 89.3 % of the essay packets, with a throughput of 14.3 Kbit/s. This shows that an ad-hoc routing protocol must quickly adapt to link changes even for long lasting routes as in this case where mobility is very low. Table 12: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 0.0439350 75.6% 12.1 Kbit/s 21510 0.052 s 5250 16260 44054 6406036 5.32 Conference simulation results. DSR - 1 0.0439350 97.1% 15.55 Kbit/s 21510 0.210 s 614 20896 3129 3689865 5.73 DSR - 2 0.0439350 98.0% 15.7 Kbit/s 21510 0.23 s 422 21088 4109 4093220 5.79 54 AODV - 1 0.0439350 89.3% 14.30 Kbit/s 21510 0.26 s 2298 19212 43881 1660020 6.62 AODV - 2 0.0439350 92.3% 14.79 Kbit/s 21510 0.29 s 1644 19866 14537 610884 6.53 AODV - 3 0.0439350 94.0% 15.00 Kbit/s 21510 0.39 s 1376 20134 54677 2112716 6.45 Both versions of DSR have the lowest packet overhead in this scenario, while all versions of AODV show the lowest byte overhead. The large byte overhead for DSR has to waits, do with the fairly large amount of traffic and compare and contrast essay that the routes have an average hopcount that is as large as 5-6 hops.
As can be seen in Table 13. Book Report? DSDV fails to deliver 3599 packets because of route failures. Thesis? This is due to the slow response time when links go down and the time it takes to find new routes. A lot of packets will be sent using a route that the protocol thinks is valid, while in hachiko book report fact the route is andreas dissertation broken and the packets are dropped. Also a lot of waits book report, packets are dropped in andreas dissertation the interface queue. AODV using only hello messages show the waits book same tendency, dropping 1364 packets because of the same reasons. It is essay however fewer packets than for DSDV. This has to book, do with the time between the compare and contrast film essay HELLO messages. The less time between the messages, the faster can the protocol react to broken links and avoid dropping the waits packets. In general, most of the packets are dropped in the sendbuffer. Retransmission of these dropped packets could of course be handled by upper layer protocols, such as TCP.
Table 13: Cause for drop Sendbuffer Route failures ARP Interface queue End of dahmen dissertation, simulation DSDV 3599 74 1567 10 Packet drops in conference scenario. DSR – 1 519 30 34 18 13 DSR – 2 303 98 4 0 17 AODV –1 894 1348 22 4 30 AODV – 2 1364 201 21 10 48 AODV -3 1096 202 14 0 64 5.6.3 Event coverage This scenario simulates a group of 50 highly mobile people that are changing position quite frequently. Hachiko Waits Book Report? It could for instance represent a group of reporters that are covering a political event, music concert or a sport contest. In real life it would be nearly impossible to establish a wired network between the greener essay reporters, but they must be in constant communication with each other, enabling a fast reaction. Parameters that are specific for the event coverage scenario are shown in Table 14. Table 14: Parameters used during event coverage scenario. Parameter Number of waits report, CBR sources Number of receivers Number of dissertation, flows Value 9 45 45 The scenario is characterized by: N N N N N Rather high mobility factor. Typically 50 % of the nodes are constantly changing their position during any time of period.
Every now and then the waits nodes tend to cluster. Links involve a few hops and relatively short-lasting. Traffic is spread all over the place. Essay? Many obstacles. Nodes can usually only communicate with a few nodes. This will lead to a low interference from the other nodes, except for waits, the moments of clustering. 55 The scenario tests the protocols: N N Ability to respond to fast link changes and fluctuating traffic. Message overhead with constant topology updates. Figure 24 shows how the essay nursing scenario was designed. 50 % of the nodes are moving randomly with a constant speed of 1 m/s. Every now and then a temporary cluster contain approximately 10 nodes will form.
These clusters remain static for waits book, a certain amount of time. Graduate Essay? Temporary clusters = Node = Obstacle Figure 24: = Movement Event coverage scenario. The results for the event coverage scenario are shown in Table 15 and Table 16. As Table 15 shows, the hachiko book report two protocols that has the lowest fraction of packets received are DSDV and the AODV version that entirely relies on feedback from link-layer. Place Essay? These protocols only have a fraction of packets received that lies around 91-92 %. For all other protocols/versions this value is at least 94 %. Report? The mobility factor for the scenario is 0.72, which is dahmen quite low even though considering we have about 50 % of the nodes in hachiko report movement. The nodes are however only moving with a speed of 1 m/s. Good? DSDV has the highest overhead of all the protocols, counted in waits book report both number of control packets and bytes. DSR both with and without eavesdropping have a very low overhead. It must however be noted that the traffic load in this scenario is jackson turner thesis about the american frontier very low and most of the communication is taking place in hachiko waits book report a very small area, thus leading to a very low average hopcount of approximately 1.5 for all protocols. In this scenario, AODV with only hello message shows better results than AODV with only link-layer support and the reason is that the hello messages makes it possible to keep track of neighbors. Nursing? Most of the communication is taking place within clusters, so to know the neighbors will probably mean that we will not have to hachiko waits, make as many requests.
The topology of the network is changing quite frequently. This causes a protocol like DSDV to have a very large overhead. Andreas Dahmen? The communication however, take mostly place within the clusters. This makes the job for the on-demand-based protocols much easier. The hopcount from report, source to andreas dahmen, destination is very small so the hachiko waits protocols will find a route very quickly. The protocols which are entirely on-demand will have a slightly 56 higher delay and the protocols that uses some sort of periodic messages (DSDV and the ADOV version that use hello messages) will have lower delay.
Table 15: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 0.721611 91.4% 14.75 Kbit/s 4500 0.075 s 385 4115 42415 10578764 1.46 hops Event coverage simulation results. DSR – 1 0.721611 97.5% 15.68 Kbit/s 4500 0.138 s 111 4389 1056 141196 1.53 hops DSR – 2 0.721611 97.7% 15.71 Kbit/s 4500 0.140 s 102 4398 1354 158420 1.57 hops AODV – 1 0.721611 94.5% 15.33 Kbit/s 4500 0.024 s 245 4255 31342 1137752 1.55 hops AODV – 2 0.721611 92.2% 14.89 Kbit/s 4500 0.214 s 352 4148 2722 117904 1.75 hops AODV – 3 0.721611 95.1% 15.36 Kbit/s 4500 0.015 s 219 4281 31443 1142180 1,55 hops Table 16 shows that most of the graduate nursing packets are dropped due to route failures and in those cases where there exists a sendbuffer, congestion/time-out in hachiko waits report the sendbuffer. AODV that only greener place essay, uses link-layer support (AODV 2) has most of the dropped packets due to failed ARP requests and DSDV drops most of its packets at the interface queue. Table 16: Cause for drop Sendbuffer Route failures ARP Interface queue End of waits book report, simulation DSDV Packet drops in event coverage scenario. DSR - 2 81 19 1 AODV - 1 100 83 61 1 102 48 235 DSR – 1 81 21 9 9 AODV - 2 131 32 178 10 1 AODV - 3 100 15 104 5.6.4 Disaster area This scenario represents some sort of disaster area in good essays about goals a region that lacks any sort of book report, telecommunication infrastructure. On Flower Garden? It could for instance represent a natural disaster or a large rescue operation. Every rescue team member could have a personal communicator with ad-hoc network capability. These personal communicators are capable of communicating with each other and with relay nodes that are mounted on a vehicle, like a helicopter, car or boat.
The parameters that are specific for hachiko, the disaster area scenario are shown in Table 17. Table 17: Parameters used during disaster area scenario. Parameter Number of CBR sources Number of receivers Number of flows 57 Value 38 87 87 The scenario is characterized by: N N N N N N A node movement, where approximately 95 % of the nodes are moving slightly, while the remaining 5 % are changing their position very often. Network partitioning now and jackson turner then. Long and short lasting links that only are a few hops.
Traffic that is report spread all over the nodes. Essay? Many obstacles. Low interference from the other nodes. The scenario tests the protocol: N N Ability to work with both slow and fast changing network topologies. Book Report? Ability to good career goals, cope with network partitioning. Figure 25 shows how the scenario was designed. There are two highly mobile nodes moving at the speed 20 m/s back and book forth. There are also three separate subnetworks that can connect to each other through the relays mounted on the highly mobile nodes. Within each subnetwork, the movement is on flower garden randomized at waits report, speed 1 m/s.
Subnetwork 2 Subnetwork 1 Vehicle 1 = Node Subnetwork 3 = Obstacle Figure 25: Vehicle 2 = Movement Disaster area scenario. The results for the disaster area scenario are shown in Table 18 and Table 19. Greener Place Essay? The calculated mobility factor for report, this scenario is quite high. Many of the nodes are moving slightly (people), and some nodes are moving very fast (vehicles). The protocols that show the best results in this scenario are the purely reactive approaches, that is AODV using both hello messages and MAC support and DSR with eavesdropping. They have a delivery ratio between 54–58 % of the packets with an average throughput of greener essay, 14.1 – 14.8 Kbit/s. DSDV has the worst performance, delivering only 29,5% of the packets with an average throughput of 12.42 Kbit/s. A delivery ratio of only 58 % for the best protocol may sound like a terrible ratio, but because of network partitioning, it is hard for any protocol to successfully deliver more packets than that. 58 DSDV show the lowest delay, but this is due to the low delivery ratio. All versions of AODV keep an average delay between 0.89 – 1.05 seconds, while the DSR versions lie between 1.19 – 1.25 seconds. Both DSR versions keep a low packet overhead compared to the other protocols.
The byte overhead is however twice as large for DSR compared to AODV. As expected, DSDV uses the hachiko book report shortest paths with an nursing average of 3.42 hops. The other protocols has an waits book report average hopcount of 5.0-5.2 hops. Table 18: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 1.154619 29.5% 12.42 Kbit/s 29616 0.196 s 20867 8749 41402 6497476 3.42 hops Disaster area simulation results. DSR – 1 1.154619 58.0% 14.79 Kbit/s 29616 1.252 s 12440 17176 27048 4880992 5.01 hops DSR – 2 1.154619 54.50% 14.43 Kbit/s 29616 1.187s 13464 16152 30692 5137148 5.16 hops AODV – 1 1.154619 48.0% 13.07 Kbit/s 29616 0.888 s 15382 14234 61557 2426164 5.23 hops AODV – 2 1.154619 52.2% 13.49 Kbit/s 29616 1.052 s 14161 15455 50686 2426164 5.24 hops AODV – 3 1.154619 54.0% 14.09 Kbit/s 29616 0.988 s 13635 15981 77311 3096228 5.26 hops DSDV drops a lot of packets because of route failures. In this scenario, DSDV also drops a large amount of packets in questions the interface queue.
One large cause for drops in waits book report the other protocols, lies in graduate questions the sendbuffer. If routes are not found within time, packets in the buffer are dropped because of timeouts or congestion. Another large cause for packet drops is route failures. This scenario is very interesting and should be investigated further, especially for the AODV protocol. We discovered when running the simulations that AODV tend to form short lived routing loops. Since the hachiko waits book report author claim that this protocol should be loop free at all times, one possible cause for this might be invalid use of the sequence numbers or the fact that sequence numbers are unsynchronized during network partitioning. Very few packets were dropped because of this (less than 5). Another interesting thing with this scenario is andreas that all main nodes send traffic both ways to each other.
This causes AODV to respond to hachiko report, requests with temporary routes set up by other requests. Since it is good about goals unclear from the draft whether the temporary routes should be regarded as a normal route in the routing table or not, we decided to try both in this scenario. By only hachiko, allowing RREPs to use the temporary routes, and by not allowing a node to respond to place essay, a RREQ with a temporary route, the routing loops could be avoided. However, the performance of the protocol decreased. We therefore used simulations where we considered the waits book report temporary routes as a normal route.
Table 19: Cause for drop Sendbuffer Route failures ARP Interface queue End of simulation DSDV 15853 479 4528 7 DSR – 1 10033 1990 35 3 1 Packet drops in disaster area. DSR - 2 10277 2960 64 159 9 59 AODV – 1 9836 5047 292 34 2 AODV - 2 10693 3046 241 20 1 AODV - 3 10941 2470 64 44 116 5.6.5 Summary realistic scenarios The realistic scenarios show how the protocols behave in certain situations. For this purpose, three scenarios were designed and simulated with different versions of the protocols DSDV, DSR and AODV. DSR show the best performance results overall. If source routing is undesirable, another good candidate is AODV with only compare and contrast film essay, MAC layer support.
It has a slightly higher packet overhead, but an overall good delivery ratio. Book? 5.7 Observations The protocols that we have worked with most are AODV and DSR, thus we have observed some important differences for greener, these protocols, that in hachiko book some way affect the performance of the protocols. Greener Place Essay? 5.7.1 Ability to find routes AODV To illustrate AODVs ability to waits report, find routes, we use a simple scenario (see Figure 26). Compare And Contrast Film? The scenario consists of four nodes A, B, C and D connected to each other. A C D B Figure 26: Simple example scenario. Node A needs a route to node D. No data has been sent earlier, thus the hachiko report only routes known to the AODV protocol are the different neighbors in the scenario. This is essay on flower garden because AODV uses hello messages to keep track of the neighbors of a node. A RREQ is generated by node A and broadcasted to its neighbors. The RREQ propagates through the network until it reaches node C. Book Report? Since node C has a route to node D it can comply with the RREQ and generate a RREP.
During the propagation of the RREQ, a reverse path is set up to node A. Essay? The RREP is unicasted back to A. It uses the waits temporarily backward route set up by the RREQ. Greener? During the propagation of the reply, a forward route is waits book set up to node D by all intermediate nodes, resulting in the routing table shown in Table 20, thus all temporary routes are updated to active routes. Table 20: Node A Destination Nexthop B B D B Routing tables for AODV after a route discovery process. Node B Destination A C D Nexthop A C C Node C Destination B D A Nexthop B D B Node D Destination C Nexthop C After the route discovery process, only B and on flower garden C have routes to hachiko waits book report, all other nodes in and contrast film essay the scenario. Node A does not know that there is report a route to node C, nor does node D know of the dissertation route to hachiko book, A and B. Thus AODV has to andreas dahmen, go through the route discovery process several times to discover all the routes. This leads to more control traffic and higher delays.
On the other hand, it saves memory by not having to keep information about routes that might not be used. 60 DSR The ability to find routes differs slightly between the DSR and AODV protocol. DSR can make use of the source route carried in each packet header to report, discover routes to nodes by which the packet has traveled through. Good Goals? If new routes are found, DSR can take advantage of this without having to go through a new route discovery phase, thus reducing the number of control packets and book report decreasing the delay. The memory usage of a node is instead increased by having to compare film essay, store more routes.
We consider the same scenario as for the AODV protocol (Figure 26). Node A needs a route to node D. Waits? No data has been sent earlier, thus DSR has no knowledge of any routes. Since no routes are known, the RREQ propagates until it reaches node D. During the propagation of the RREQ, every node in its path learn a route back to all the nodes by on flower garden which the RREQ has passed through. The RREP is waits unicasted back to A, using the routes learned during the propagation of the good career goals RREQ. As the RREP propagates, each node also learns the waits book routes to andreas dahmen dissertation, all nodes for waits book, which the andreas dahmen RREP has passed through, resulting in the routing tables shown in Table 21. After the route discovery phase, each node has a route to every other node in this example. Table 21: Node A Destinatio n B C D Path B B-C B-C-D Routing caches for DSR, after a route discovery process. Hachiko Book Report? Node B Destinatio n A C D Path A C C-D Node C Destinatio n A B D Path B-A B D Node D Destinatio n A B C Path C-B-A C-B C 5.7.2 Temporary backward routes When a RREQ propagates in search for a route in AODV, a temporary backward route is set up towards the good about career goals requesting node.
A RREP might use this backward route. This route is normally set to expire after 3 seconds if it is report not used. It is not clear from the draft if this route may be used by application data as well. Using this route for data affects the place behavior of the protocol in some way and book report it is not described how the protocol should handle this. One of the andreas dahmen dissertation problems with this temporary route is with the way it is set up. When the RREQ propagates, we do not know who will be using the backward route, so no active neighbors can be put into the active neighbor list. If during this time, a link failure or an expired route entry somewhere breaks the route, the rest of the nodes in the route are not informed of this and hachiko waits book report therefore have redundant routes in their tables.
When the route is used again, the application data will come to greener, a node in the route that does not have a valid entry for hachiko waits book, the destination and dissertation will therefore be dropped while a triggered RREP tries to inform the nodes in the route that it is broken. This problem will become more apparent in a network with a higher load. Another problem is the short lifetime if temporary routes are installed into the routing table. Lets say node A sets up a temporary route to D. Node A can then respond with the temporary route to another request searching for a route to D. Waits? Since the temporary route has a short lifetime, it might expire before the actual data has a chance to use it. This results in unnecessary control overhead and packet drops. To deal with this, the routing agent could chose to only allow RREP to use the temporary route. Turner Frontier? Also a check of the waits report expire time before responding with a RREP could be used to assure that the route wont timeout shortly after the node has responded with the greener place essay information.
A question about hachiko, this was directed to the author of the protocol with the response that this check should not be done, instead the good goals protocol should rely on the sequence numbers to provide the freshness of a route. We implemented a version of the AODV protocol that used the temporary route for all packets since it showed a slightly better performance result then if not allowing data packets to use the temporary route. The implementation done in Gothenburg used the hachiko waits report temporary route only for route replies. So we have a small difference in our implementations. 61 5.7.3 Buffers The use of graduate nursing, send buffers in the routing protocol also affects the performance of the routing protocol; especially the size of the buffers and the time a packet is allowed to hachiko, stay there before it is dropped. The send buffer buffers data packets while the routing protocol requests a route to the destination. In our simulations, AODV used a buffer capable of holding 64 packets and allowing them to about the american frontier, stay in the buffer for maximum 8 seconds. Allowing the packets to stay in hachiko waits book the buffer for good, longer period of hachiko book, times will of course increase the amount of successfully routed packets, but also increase the average delay. Also the frederick turner about frontier choice of queuing discipline will affect the measured performance.
If the buffer is full, there must be some smart algorithm to decide which packets should be dropped. Hachiko Report? The routing protocol could decide not to buffer any packets at all and good essays career depend on higher layer protocols such as TCP to retransmit lost packets. Hachiko? This would however affect the measured performance in the simulations and give unfair results for the protocol. 5.8 Discussion If we compare the compare essay work that we have done against the work that was done by waits book the CMU Monarch project , many similarities can be seen. Their conclusion was that both DSR and AODV performs well at all mobility rates and movement speeds.
We have come to the same conclusion, but we feel however that their definition of mobility (pause time) does not represent the dynamic topology to the same extent as our mobility factor that is based on the actual relative movement pattern. The only node speeds that they have tested are 1 m/s and 20 m/s, which are not showing the complete range. Our mobility factor has a speed range from 0 m/s up to 20 m/s and shows how the protocols behave in questions the complete range. Hachiko Waits Report? They have also only shown the result for one DSR version and one AODV version. The DSR version that they show the results for is using eavesdropping, which we regard as being unrealistic, because of the security issuses discussed earlier. The AODV version that they have used is not using hello messages, which changes the behavior of AODV. About Career? We have tested different versions and hachiko shown that DSR with eavesdropping has a slightly better performance than DSR without eavesdropping. We have also shown that AODV with MAC-layer support and essay hello messages has better performance than AODV with only MAC-layer support. Our results also show that it is necessary to use some support from the MAC-layer to achieve a performance that is good even at high mobility factors. Hachiko Report? The CMU Monarch project, have used the number of sources as a definition of the load that is offered the network. Their simulations with the essay nursing different number of sources are almost identical to each other.
The only protocols that showed a significantly difference was TORA, that only delivered 40 % of the packets with the lowest pause time and highest number of sources. Our definition of load was based on the rate that the sources are sending packets with. Even DSR that had the best results in the CMU paper fails to deliver a large fraction of the waits book packets when the rate is increased. The increase of the rate also very clearly shows how much the overhead for DSR increases compared to for instance AODV. Compare And Contrast Film Essay? 5.9 Classification Why is there any need for classification of routing protocols? If one routing protocol is hachiko superior than the other routing protocols for instance in very high mobile environments, why not always use that routing protocol? If it handles high mobile environments, it should also be good at low mobile environments. In real life, many parameters affect the behavior of the routing protocol.
It is also important to recognize the need that is required in essay questions a particular scenario. In one scenario, there is maybe more need for high throughput than there is for low delay. In another scenario there is maybe more need for low delay etc. This is becoming more and more important now, in book particular when active networks  is becoming an interesting issue in essay on flower networking. Active networking means that you add user controllable capabilities to hachiko waits report, the network. The network is no longer viewed a passive mover of bits, but rather as a more general computation engine. This makes it possible for instance to adjust the greener routing protocol depending on the scenario. You could basically send the routing protocol and let it install itself into the nodes. 62 5.9.1 Mobile networks As the simulation results show, the mobility of the network greatly affects the performance of the protocols. It is crucial that the protocol ability to detect broken routes is fast enough and that they also react to book, these changes.
DSDV Since DSDV is dependent of its periodic updates, its ability to deal with a dynamic topology is very poor. Good Career Goals? It has a poor ability to fast detect broken links and hachiko report takes time to converge. This protocol should really be avoided for use in ad-hoc networks where it is crucial to deal with frequent changing topology. This protocol could however be an option for networks that are static during long periods of essay questions, times. AODV The original AODV protocol using only HELLO messages as link breakage detection shows poor results as mobility increases. This protocol needs better link breakage detection. Hachiko Report? Using lower layers such as MAC to detect transmission errors can achieve this. If this is used, the protocol actually shows a very good performance. This protocol is film essay a definite choice for highly mobile networks. Report? DSR This protocol is highly optimized and also shows good results in the simulations.
The protocol could definitely be used in highly mobile networks as well as static networks. 5.9.2 Size of networks When talking about the size of a network, it is garden not only the number of nodes in the network that is of interest. The area that the nodes are spread out over is also interesting. This basically decides the waits report connectivity of the and contrast film essay network. Waits? A large area with many nodes may mean longer routes then for a smaller area with the same number of nodes.
At the same time, many nodes close to each other means a higher collision probability. DSDV This protocol does not scale well. Its use of periodic broadcasts limits the protocol to small networks. Andreas Dissertation? If the hachiko waits book protocol would be used in large networks, the converge time to a steady state would increase when routes go up and down. The reason is that updates must propagate from one end of the network to the other. AODV This protocol scales well, and could be used in both small and medium sized networks. The combination of on-demand and distance vector makes this protocol suitable for large networks as well. The information that each node must store for each wanted destination is rather small compared to for instance DSR that has to store whole source routes. In large networks however, the garden propagation of requests to all nodes is a waste of resources. A better solution is probably to divide the network into clusters or zones, like for instance ZRP and CBRP have done. Book Report? DSR This protocol has some limitations when it comes to the size of the network.
A larger network often means longer routes and longer routes means that the source overhead in each packet grows. The current implementation limits each packet to carry a source route of maximal 16 hops. This can of course be adjusted, but one should keep in mind the large overhead this causes. One could imagine a network with 20 nodes connected in graduate essay a straight line. Then this implementation would not manage to route to all nodes. Waits Report? We therefore recommend this protocol for small and medium sized networks.
63 5.9.3 Network scenarios Conference For low mobility scenarios, like the conference scenario that we did simulations on, DSR is the best protocol to use if the essay garden hopcount is small (fewer than 5 hops). The reasons are high delivery rate, low delay and low message overhead in terms of packets and hachiko waits book byte overhead. If the number of good essays, hops increases and get as many as 10 hops, each packet must carry a very large byte overhead, which can be very costly, when the load increases. Waits? Another good candidate for this scenario when the number of frederick thesis the american frontier, hopcount increases is one of the AODV versions that use MAC-layer support. AODV has also a very high delivery ratio, but the number of control packets is somewhat larger.
Event coverage In average mobile scenarios, like the event coverage scenario, where nodes tends to waits book, cluster and almost all communication is within the clusters, DSR is by all means the best protocol. It has a very large delivery ratio and the overhead is very small, even counted in bytes, because of the few hops required to about career, reach the destination. Hachiko Book Report? The AODV versions show a very good result also, but the greener overhead is larger. So for these type sort of networks DSR it the best protocol. Hachiko Waits? Disaster In networks that become partitioned, DSR with eavesdropping show the best results in this scenario. It has a high delivery ratio, high throughput, a delay around 1.2 seconds and andreas dahmen dissertation low packet overhead.
It also uses only 5 hops in average to reach a destination. This protocol is therefore recommended in this type of scenario. Eavesdropping might however be undesirable because of security issues. One other candidate for this scenario is AODV with MAC support. Hachiko Waits Book Report? It has almost as high delivery ratio as DSR and also a lower delay. The packet overhead is twice as high but the byte overhead is and contrast smaller. Hachiko Book? 5.10 Improvements The simulations have shown that DSR with and without eavesdropping and on flower garden the AODV versions that use linklayer support has the overall best result in waits report almost all simulations. DSR has as mentioned earlier the advantage that it learns more information for each request it sends out. If a request goes from S to greener place essay, D and the reply from D to S, S will learn the route to all intermediate routes between S and hachiko waits D. This means that it is not necessary to send out as many requests as for example AODV.
The source routing approach is therefore very good in frontier the route discovery and hachiko book route maintenance cases. However, source routing is not desirable to use for data packets. First of all, it adds a lot of overhead. Secondly it is not as traditional as for instance distance vector or link-state that are widely used in wired networks. Compare? Our proposal is therefore to implement a protocol that is a combination of source routing and distance vector. Source routing should be used in book report route discovery and route maintenance phases. These phases would also include that the essay on flower garden routing tables where set up accordingly during the propagation of the requests and replies. Report? When the essay on flower garden data packets are forwarded a distance vector algorithm should be used. The packets are simply forwarded to hachiko report, the nexthop according to andreas dissertation, the routing table. This in hachiko waits report combination with that the protocol stores several routes for each destination would probably mean a protocol with a performance that is essay nursing even better than the book report protocols that have been simulated in this master thesis.
64 6 Implementation study The implementation study that was conducted at Ericsson Mobile Data Design in garden Gothenburg  has implemented the AODV protocol. Hachiko Waits Report? The goal was to deliver a working routing protocol as specified in the original AODV draft . 6.1 Design Main Event Queue Route Table Send Hello Send Request Check Neighb Check sender Remove route Neighbors / Senders Lookup Add Delete Update Need route? Add Delete Update time Is member? Host unreachable Lookup failed Message Request buffer Send request Send reply Send hello Receive msg Add Delete Is member? Rreq Rrep Hello Route add Route del User space /dev/route Iotcl() Icmp.c UDP FIB Kernel Table Kernel route.c Other daemons Figure 27: Overview of film essay, AODV daemon. Hachiko Waits Report? The implementation that has been done should only be considered as a prototype to confirm the usefulness of AODV. It is implemented as a daemon in user space. The advantage with this is garden that debugging and testing is much easier to do.
A final implementation should be made in hachiko book kernel space with more optimized design. Dissertation? Thus abandon the modular design and optimize the code to hachiko book report, go really fast. Figure 27 shows the design of the user space daemon and turner about frontier how it interacts with the kernel code. The different modules will be explained in the following chapters. 6.1.1 Main Main ties together all other modules of the user space daemon. It is also in main that the AODV specific code lies. 65 6.1.2 Event queue Queue for events that are supposed to be performed at hachiko book, certain times. These events include: N N N N Periodic hello messages Send / retransmit route requests Timeouts of route entries Hello timeout 6.1.3 Route table This module is an interface against the submodules Daemon Table and Kernel Table. It takes care of these two, so when you want to lookup or change a route from Main, you only dahmen dissertation, have to do one call to this module instead of two to waits, the both submodules.
The entries in Daemon Table module have all the fields that is required for AODV, sequence number, list of active neighbors and so on. The operations supported are Lookup, Add and Delete. The Kernel Table is not a table in the sense Daemon Table is, instead this submodule just communicates with the kernel, sending messages about adding and deleting entries and receives netlink need-route messages. Good Career? 6.1.4 Neighbors / senders Keeps track of the neighbors of a node. A neighbor is a host that sends/receives hello messages that is directly received/sent by another node. Book Report? This demands that the links are bi-directional. At first it was thought that the WaveLAN cards would take care of this, but it was not the case. The signal strength and graduate the range was different between the hosts. To be able to guarantee bi-directional link, the waits concept Sender was added. A host is classified as a sender if it can be heard by at least one other node. When sending hello messages a node sends the graduate questions list of current Senders and if the receiver of the hachiko waits book report Hello messages is in this list, it is good essays about career goals a Neighbor and hachiko waits book report can start act as one 6.1.5 Request buffer This buffer prevents the network of essay on flower, being flooded by multiple request for the same address.
This buffer stores already processed requests. Hachiko Waits Book? 6.1.6 Message Handles the different types of graduate nursing, messages that the daemon can send and report receive. These messages are: N N N Hello Route Request Route Reply. 6.2 Setup The computers used for this implementation study was: N N 2 stationary computers with Lucent WaveLAN ISA cards. Place Essay? 3 laptops with Lucent WaveLAN PCMCIA cards.
The implementation started first with the waits 2 stationary computers running FreeBSD7. Andreas Dahmen Dissertation? The choice of FreeBSD was primarily made because FreeBSD offers the best documentation of book report, its kernel source. It was later discovered when the laptops arrived that FreeBSD was incompatible with the Lucent WaveLAN PCMIA cards in frederick the american the laptops. Linux8 however has support for both variants of the LucentWaveLAN cards and Linux was therefore chosen as development operating system. Book? It is not very hard to dahmen dissertation, port the code to FreeBSD in the future if so desired. 7 8 FreeBSD 2.2.6 Linux Red Hat 5.1 66 6.3 Testing The purpose of testing the book report implementation is to verify that the andreas implementation works correctly and to see if the waits book performance is suitable for real life applications. 6.3.1 Correctness To verify that the implementation of AODV behaved correctly, computers were placed in different scenarios to test the different parts of the protocol. The following tests where made: N N N N N N N Bi-directional links and andreas neighbors: Tests that two nodes can send hello messages to each other and registry the counterpart as a neighbor. Unidirectional links and neighbors: It tests the same as above, but with the difference that we only hachiko, have an uni-directional link, so only one of the nodes can hear the other and garden registry him as a neighbor. Neighbor link down: Tests that neighbors moving away from each other causes the link between them to go down. Zero hop route requests: Tests that a request to a neighbor that also is the requested destination generates a reply that is correctly received.
This is not the normal operation of the protocol, but could happen if two nodes are in range but have not accepted each other as neighbors. Single hop route request: Tests the situation where node S searches the route to D and we have one node B in between. S broadcasts a request that is caught by B, which knows the report route to D and sends a reply back to S. Multihop route request: Almost the same situation as the single hop route request. The difference is that we have two nodes between the essay on flower requesting source and hachiko waits book report the destination. The route request must therefore be forwarded one hop before a reply can be generated.
Triggered route reply: Tests that the jackson thesis about the american triggered route reply is generated whenever a route goes down. 6.3.2 Performance No actual performance tests were done. The results for so few nodes would be misleading. Instead tests with real applications like Netscape and hachiko book report Telnet were done. The problems that occurred with these tests were related to the on-demand nature of essays goals, AODV. Telnet for instance returns host-unreachable when trying to telnet to a computer on the first attempt. The second attempt however is successful. The reason is hachiko report that when Telnet makes its first attempt, no route to the destination exists.
This will result in an error message from the kernel to Telnet, at the same time as a new request is andreas dissertation sent to the neighbors. This request will eventually find a route to the destination and hachiko book report it is good career goals installed in the routing table. When Telnet makes a second attempt connect to the same host, a route will already exist in the routing table and telnet will successfully reach the destination host. Hachiko Book Report? The solution to this problem is simply to dissertation, take care of the waits book error messages that the kernel sends to the application. The error message should be buffered and essay questions if a route is not found in a certain amount of time, the error message should be sent to the application, but if a route is actually found the error message can be discarded. 6.4 Problems / Limitations Problems that occurred during the implementation include: N N N FreeBSD incompatibilities: As mentioned before, lack of hachiko waits, functional drivers to FreeBSD forced the implementation study to be done under Linux. Address: The current prototype requires that each node participating in the network have a predefined unique IP-address. There is a great need for a dynamic assigned IP-address architecture, which assigns nodes IP-addresses as they enter the network. Graduate Essay Nursing? IPv6 holds such functionality. This prototype is however done for IPv4 so no consideration has been done to implement such functionality. Three-way handshake: To guarantee bi-directional links, a three way handshake was necessary for the hello messages before two nodes can be certain of the other nodes existence.
The handshake uses piggybacking. It concatenates a list of all nodes it receives hello messages from to the hello messages it sends. When a node receives a hello message and finds its own address in the concatenated list it will add the sending node to its own list of neighbors which it has bi-directional links to. Three hello 67 N messages instead of one wastes bandwidth, but could also in a worst case scenario mean that it could take as long as two full hello intervals before two nodes in range of each other accepts the bi-directional links. Hachiko Report? Temporary routes: When a request is broadcasted from graduate questions, a node, it will propagate through the network and at the same time install a temporary route back to hachiko waits report, the source.
The problem with this temporary route is first of all that the request is unaware of and contrast, if the route ever will be used and secondly who will use it. This means that it does not know the active neighbors that are using this entry and can therefore not inform these neighbors if a link should go down on waits book report, this route. The solution that was implemented differs somewhat of what was done in the simulation study. The solution is to good career goals, store the temporary routes separately and only install them in the routing table when the hachiko waits route reply is essay propagating back through the network. 6.5 Improvements Possible features that could be added to this prototype: N N N N Link layer hellos: The addition of link layer feedback from 802.11 would significantly increase the hachiko waits book performance as the simulation study has shown. Redundant routes: Store all routes to a destination, not only the one we are currently using. If a route goes down due to a link failure, the next stored route would be tried before a new request is to be sent. This saves a lot of frederick turner about the american frontier, overhead a and hachiko makes the delay somewhat smaller. Dynamic IP-addresses: As mention under limitations, dynamic address assignment is dahmen a requirement for these kind of networks.
Multicast: Multicast groups within a ad-hoc network could be added. The latest AODV draft has support for this. 6.6 Implementation conclusions The implementation of the AODV protocol has shown that it is possible to book, get these protocols to turner thesis about the american, work in real-life. It must however be noted that real-life in this case only hachiko book, consisted of five computers. Good Essays Goals? The AODV prototype has also given some insight into the problems that arise when trying to run real applications on an ad-hoc network. Waits Book Report? Applications like Netscape and Telnet get host unreachable in the first attempt. Jackson Turner Thesis? The second attempt finds the route successfully. This has to do with the hachiko waits on-demand feature of the AODV protocol.
68 7 Conclusions 7.1 Results The simulations have shown that there certainly is good about goals a need for a special ad-hoc routing protocol when the mobility increases. It is however necessary to have some sort of feedback from the link-layer protocol like IEEE MAC 802.11 when links go up and down or for neighbor discovery. To only be dependent on periodic messages at hachiko waits, the IP-level will result in good a very high degree of packet losses even when mobility increases a little. The simulations have also shown that more conventional types of protocols like DSDV have a drastic decrease in performance when mobility increases and are therefore not suitable for mobile ad-hoc networks. AODV and waits DSR have overall exhibited a good performance also when mobility is high.
DSR is however based on source routing, which means that the byte overhead in each packet can affect the total byte overhead in the network quite drastically when the offered load to the network and the size of the network increases. In these situations, a hop-by-hop based routing protocol like AODV is turner thesis the american more desirable. One advantage with the source routing approach is however that in its route discovery operation it learns more routes. Source routing is hachiko waits book however not desirable in ordinary forwarding of data packets because of the large byte overhead. A combination of AODV and DSR could therefore be a solution with even better performance than AODV and DSR. Another key aspect when evaluating these protocols is to test them in realistic scenarios. Graduate Questions? We have tested them in three types of scenarios. Hachiko Report? DSR had the andreas dahmen dissertation best performance, but the large byte overhead caused by the source route in book each packet makes AODV a good alternate candidate.
It has almost as good performance. The implementation study conducted at ERV in Gothenburg has shown that it is possible to get a real ad-hoc network up and running. The main problems that did occur were related to the testing of the protocol with real applications. When a route was needed by andreas dahmen dissertation the application and book report the route did not exist in the routing table, the andreas dahmen kernel informed the applications of hachiko book, a connection error before giving the routing protocol enough time to find a route. 7.2 Further studies Ad-hoc networking is a rather hot concept in computer communications.
This means that there is much research going on and many issues that remains to be solved. Due to limited time, we have only focused on andreas dahmen dissertation, the routing protocols. Hachiko Waits? However there are many issues that could be subject to further studies. First of greener place essay, all, the simulator environment could be improved. These are just some of the waits improvements that could be made: N N More routing protocols, for instance TORA, ZRP and CBRP. Measurement of computing complexity.
Secondly, there are many issues related to ad-hoc networks that could be subject to andreas dissertation, further studies: N N N Simulations which take unidirectional links into consideration. Some sort of analysis of whether many small control messages are more costly to send in terms of hachiko waits book, resources than fewer large control messages. Security: A very important issue that has to be considered is the security in an ad-hoc network. Routing protocols are prime targets for impersonation attacks. Because ad-hoc networks are formed without centralized control, security must be handled in a distributed fashion.
This will probably mean that IP- 69 N N N N N N Sec  authentication headers will be deployed, as well as the necessary key management to distribute keys to questions nursing, the members of the waits book report ad-hoc network. Quality of and contrast film essay, Service (QoS): What needs are there for Quality of Service in an ad-hoc network? This is related to what the networks actually will be used for. Hand-over of real-time traffic between nodes. How should real-time traffic smoothly be handed over to another node when a route goes down? Should flooding be used before a route is found? Multicast: We have only looked at unicast routing. Multicast routing is waits report also an interesting issue that has to be considered.
Connecting ad-hoc networks to jackson turner thesis about frontier, the Internet through access points: How do you connect an ad-hoc network to the Internet? It is not possible to just add the hachiko access point as default in on flower garden the routing tables. Hachiko? This would mean that nodes without a route to a certain destination would be routed to greener place, the Internet. Hachiko Waits Report? Mobile IP: Integration of mobile IP into ad-hoc networks. Addressing of hosts: How should the andreas dahmen hosts in an ad-hoc network be addressed? What happens if one adhoc network is partitioned in to waits book, two separate networks or two ad-hoc networks are merged into about goals one new larger ad-hoc network? IP Index Router IP Router (IP) Index Index Figure 28: Router (RID) IP IP Different router identification approaches. Hachiko? From left to right: 3a, 3b, 3c. There are basically three types of identifiers to consider (Figure 28): 1) Interface identifiers: Interfaces are present on both routers and hosts.
In the Internet addressing architecture, interfaces are identified by IP addresses. 2) Host identifiers: Can either be a permanent identifier or a temporary identifier. 3) Router identifiers: Is unspecified and generally depends on the routing policy. There are three approaches to about career, MANET router identification and addressing currently being considered: a) Single IP address (AODV): Identifies a MANET node (both the router and the host) with a single IP address. Waits Book? This approach leaves several issues open: N How to support sets or subnets of hosts attached to a MANET router?
N How to support the use of multiple wireless interfaces? b) Single IP address with interface indexes (DSR): Identifies a MANET router with a single IP address and each interface with a single-byte interface index. This makes it possible to enable simultaneous support for multiple wireless technologies, with the IP address acting as router identifier. Good Essays Career? The problem with this scheme is that it is waits report not IP in the classical sense where interfaces are identified by IP addresses. The use of a non-standard addressing architecture will likely complicate interoperability. c) Router identifier and IP interface addresses (IMEP): Identifies a MANET router with a router Identifier (RID) and garden identifies each interface with an IP address. Waits Book Report? This approach can support sets or subsets of attached hosts and simultaneous use of about career, multiple wireless technologies.
Approach a) and book b) seem tailored to support a mobile host that acts like a router. Approach c) is dahmen dissertation intended to hachiko waits book report, support a mobile router platform to career goals, which one or more host-like devices may be permanently or temporally affiliated. These approaches say nothing about how IP addresses are assigned to interfaces (on hosts or routers), or what the RID is and how it is book report assigned. This is a separate problem, although one which is frederick jackson thesis about related to routing. 70 8 References  Dimitri Bertsekas and book report Robert Gallager, “Data Networks - 2nd ed”. Prentice Hall, New Jersey, ISBN 013-200916-1.  Bommaiah, McAuley and Talpade. AMRoute, “Adhoc Multicast Routing Protocol”, Internet draft, drafttalpade-manet-amroute-00.txt, August 1998. And Contrast Film Essay? Work in hachiko waits book progress.  Josh Broch, David A. Maltz, David B. Johnson, Yih-Chun Hu and Jorjeta Jetcheva, “A performance Comparison of Multi-hop Wireless Ad Hoc Network Routing Protocols”. Mobicom'98, Dallas Texas, 25–30 October, 1998.  Josh Broch, David B. Frederick About Frontier? Johnsson, David A. Hachiko Report? Maltz, “The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks”. Internet Draft, draft-ietf-manet-dsr-00.txt, March 1998. Essays Career Goals? Work in progress.  Scott Corson and Joseph Macker, “ Mobile Ad Hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations”.
Internet-Draft, draft-ietf-manet-issues-01.txt, March 1998. Work in progress.  M.Scott Corson, S. Papademetriou, Philip Papadopolous, Vincent D. Hachiko Waits Book? Park and Amir Qayyum, “An Internet MANET Encapsulation Protocol (IMEP) Specification”. Essay? Internet draft, draft-ietf-manet-imepspec01.txt, August 1998. Waits Book Report? Work in progress.  Kevin Fall and essay garden Kannan Varadhan, “ns notes and documentation”. The VINT project, UC Berkeley, LBL, USC/ISI, and Xerox PARC, May 1998. Work in progress.  Zygmunt J. Haas and Marc R. Pearlman, “The Zone Routing Protocol (ZRP) for Ad Hoc Networks”, Internet draft, draft-ietf-manet-zone-zrp-01.txt, August 1998.
Work in progress. Waits Book Report?  IEEE Computer Society LAN MAN Standards Committee, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, IEEE Std 802.11-1997. Good About Goals? The Institute of report, Electrical and Electronics Engineers, New York.  Philippe Jacquet, Paul Muhlethaler and Amir Qayyum, “Optimized Link State Routing Protocol”. Internet draft, draft-ietf-manet-olsr-00.txt, November 1998. Work in progress.  Mingliang Jiang, Jinyang Li and Yong Chiang Tay, “Cluster Based Routing Protocol (CBRP) Functional specification”. Internet draft, draft-ietf-manet-cbrp-spec-00.txt, August 1998. Work in progress.  David B. Johnson and David A.Maltz, “Dynamic source routing in ad hoc wireless networks”. In Mobile Computing, edited by Tomasz Imielinski and Hank Korth, chapter 5, pages 153-181. Kluwer Academic Publishers.  David B. Johnson and David A. Maltz, “Protocols for adaptive wireless and mobile computing”. In IEEE Personal Communications, 3(1), February 1996.  Stephen Kent and greener place Randall Atkinson, “Security Architecture for the Internet Protocol”, Internet draft, draft-ietf-ipsec-arch-sec-07.txt, July 1998.
Work in progress.  Mobile Ad-hoc Networks (MANET). URL: http://www.ietf.org/html.charters/manet-charter.html. (1998-11-29). Report? Work in dissertation progress. 71  Vincent D. Park and M. Scott Corson, “Temporally-Ordered Routing Algorithm (TORA) Version 1: Functional specification”. Internet draft, draft-ietf-manet-tora-spec-01.txt, August 1998. Hachiko Waits? Work in dissertation progress.  Vincent D. Park and M. Scott Corson, “A performance comparison of the Temporally-Ordered Routing Algorithm and Ideal Link-state routing”. In Proceedings of IEEE Symposium on Computers and Communication ’98, June 1998.  Charles E. Perkins, “Mobility support, Mobile IP and Wireless Channel Support for hachiko book, ns-2”, presentation slides. URL: http://www.svrloc.org/ charliep/mobins2/, (1998-11-29). Work in progress. Greener Essay?  Charles E. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Internet draft, draft-ietfmanet-aodv-01.txt, August 1998.
Work in progress.  Charles E. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Internet draft, draft-ietfmanet-aodv-02.txt, November 1998. Work in progress.  Charles E. Perkins, “Mobile Ad Hoc Networking Terminology”. Internet draft, draft-ietf-manet-term00.txt, October 1997. Work in progress.  Charles E. Perkins and Pravin Bhagwat, “Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers”. In Proceedings of the SIGCOM '94 Conference on Communications Architecture, protocols and report Applications, pages234-244, August 1994. A revised version of the paper is graduate essay nursing available from http://www.cs.umd.edu/projects/mcml/papers/Sigcomm94.ps. Hachiko Waits Book Report? (1998-11-29)  Larry L. Peterson and greener Bruce S. Davie, “Computer Networks - A Systems Approach”. San Francisco, Morgan Kaufmann Publishers Inc. ISBN 1-55860-368-9.  Plummer, D., An Ethernet Address Resolution Protocol - or - Converting Network Protocol Addresses to book, 48.bit Ethernet Address for Transmission on Ethernet Hardware, RFC-826, MIT, November 1982.  Theodore S. Rappaport, “Wireless Communications: Principles and Practice”. New Jersey, Prentice Hall. Garden? ISBN 0-13-375536-3.  Raghupathy Sivakumar, Prasun Sinha and Vaduvur Bharghavan, “Core Extraction Distributed Ad hoc Routing (CEDAR) Specification”, Internet draft, draft-ietf-manet-cedar-spec-00.txt, October 1998.
Work in progress. Book Report?  Martha Steenstrup, “Routing in communication networks”. New Jersey, Prentice Hall. ISBN 0-13010752-2.  Jerry Svedlund and frederick about the american Johan Kopman, “Routing protocols in wireless ad-hoc networks - An implementation study”. Uppsala: Uppsala University. Master thesis.  D. L. Tennenhouse and hachiko waits D. Wetherall, “Towards an active network architecture”. In Multimedia Computing and Networking 96, San Jose, CA, Jan 1996. Compare?  The CMU Monarch Project. “The CMU Monarch Projects Wireless and hachiko waits Mobility Extensions to compare and contrast, ns”. URL: http://www.monarch.cs.cmu.edu/. Hachiko Book? (1998-11-29).
Work in progress. 72 Appendix A -Terminology This appendix contains some terminology  that is related to garden, ad-hoc networks. Hachiko Waits Book Report? A.1 General terms Bandwidth: Total link capacity of a link to carry information (typically bits). Channel: The physical medium is divided into andreas dahmen dissertation logical channel, allowing possibly shared uses of the medium. Channels may be made available by subdividing the medium into distinct time slots, distinct spectral bands, or decorrelated coding sequences. Convergence: The process of approaching a state of equilibrium in which all nodes in hachiko the network agree on a consistent state about the topology of the network.
Flooding: The process of delivering data or control messages to graduate questions, every node within the any data network. Host: Any node that is waits not a router. Interface: A nodes attachment to a link. Link: A communication facility or medium over which nodes can communicate at the link layer. Greener Place Essay? Loop free: A path taken by a packet never transits the same intermediate node twice before arrival at waits, the destination. MAC-layer address: An address (sometimes called the link address) associated with the link interface of a node on a physical link. Next hop: A neighbor, which has been designated to forward packets along the way to a particular destination. Neighbor: A node that is within transmitter range from another node on the same channel. Node: A device that implements IP.
Node ID: Unique identifier that identifies a particular node. Router: A node that forwards IP packets not explicitly addressed to itself. Andreas Dissertation? In case of report, ad-hoc networks, all nodes are at graduate essay, least unicast routers. Routing table: The table where the routing protocols keep routing information for various destinations. This information can include nexthop and the number of hops to the destination. Scalability: A protocol is scalable if it is applicable to large as well as small populations. Source route: A route from the source to the destination made available by the source. Throughput: The amount of data from a source to a destination processed by the protocol for which throughput is to be measured for instance, IP, TCP, or the MAC protocol. 73 A.2 Ad-hoc related terms Ad-hoc: For this special or temporary purpose or a special case without generic support. AODV: Ad-Hoc On-Demand Distance Vector.
Routing protocol for wireless ad-hoc networks. Waits Report? Asymmetric: A link with transmission characteristics that are different of the transmitter and receiver. For instance, the range of essay, one transmitter may be much higher than the range of another transmitter on the same medium. The transmission between the two hosts will therefore not work equally well in both directions. Hachiko Waits? See also symmetric. Beacon: Control message issued by a node informing other nodes in its neighborhood of jackson turner about the american, its continuing presence. Bi-directional: see symmetric. CBRP: Cluster Based Routing Protocol. Hachiko Report? Routing protocol for wireless ad-hoc networks.
Cluster: A group of nodes typically in range of each other, where one of the nodes is elected as the essay on flower cluster head. The cluster head ID identifies the cluster. Each node in the network knows its corresponding cluster head(s) and therefore knows which cluster(s) it belongs to. Hachiko Waits? DSDV: Dynamic Sequenced Distance Vector. Routing protocol for wireless Ad Hoc networks. DSR: Dynamic Source Routing. Routing protocol for turner thesis about the american frontier, wireless Ad Hoc networks. Hachiko Waits? Proactive: Tries to graduate nursing, maintain the hachiko routing map for the whole network all the time.
See also reactive. Compare And Contrast Film? Reactive: Calculates route only upon receiving a specific request. See also proactive RREQ: Routing Request. A message used by AODV for the purpose of discovering new routes to a destination node. RREP: Route Reply. Hachiko Book? A message used by AODV to reply to route requests. Good About Goals? Symmetric: Transmission between two hosts works equally well in both directions.
See also asymmetric. TORA: Temporally Ordered Routing Algorithm. Waits Report? Routing protocol for wireless ad-hoc networks. Unidirectional: see asymmetric. ZRP: Zone Routing Protocol. Routing protocol for questions nursing, wireless ad-hoc networks. 74 Appendix B - AODV implementation for ns This appendix contains a little more details about the hachiko waits book implementation of AODV that we did for ns. The implementation of jackson turner thesis, AODV is done according to the draft  released in August 1998. B.1 Message formats AODV have four different messages that it uses for route discovery and route maintenance.
All messages are sent using UDP. B.1.1 Route Request – RREQ The format of the route request message is shown in Figure 29. 0 1 2 31 01234567890123456789012345678901 Type Reserved Hop count Broadcast ID Destination IP address Destination Sequence Number Source IP address Source Sequence Number Figure 29: N N N N N N N N Route request format. Waits Book Report? Type: Type of message. Reserved: Reserved for compare and contrast film, future use. Waits Book Report? Currently sent as 0 and ignored on reception. Hop count: Number of hops from the source IP address to the node handling the request. Jackson Thesis? Broadcast ID: A sequence number identifying the particular request uniquely when taken in conjunction with the source nodes IP address.
Destination IP address: IP address of the destination for which a route is hachiko book report required. Destination sequence number: The last sequence number received in the past by essay questions nursing the source for any route towards the destination. Source IP address: IP address of the node that originated the request. Source sequence number: Current sequence number for book, route information generated by on flower garden the source of the waits book route request. Essays About Career? 75 B.1.2 Route Reply - RREP The format of the route reply message is shown in Figure 30. 0 1 2 31 01234567890123456789012345678901 Type L Reserved Hop count Destination IP address Destination Sequence Number Lifetime Figure 30: N N N N N N N Route reply format. Waits Report? Type: Type of message. L: If the frederick jackson about frontier L-bit is set the book message is essays goals a hello message and contains a list of the nodes neighbors. Reserved: Reserved for future use. Hachiko Waits Report? Currently sent as 0 and ignored on reception. Good? Hop count: Number of hops from the source IP address to the destination IP address.
Destination IP address: IP address of the hachiko waits book destination for which a route is supplied. Destination sequence number: The destination sequence number associated to on flower garden, the route. Lifetime: Time for which nodes receiving the Reply consider the waits book report route to be valid. B.1.3 Hello Hello messages are a special case of Route reply messages. The difference is that a hello message always supplies the questions route to itself. This means that the hop count field is hachiko waits report set to 0, the destination address set to the nodes IP address and the destination sequence number set to the nodes latest sequence number.
B.1.4 Link failure Link failure messages are also special Route reply messages, but in this case the destination reflects the route that has broken. The broken route is assigned an infinite hop count and a sequence number that is increased with one. 76 B.2 Design Figure 31 shows how AODV was designed when implemented for ns. Dahmen? AODV OTcl C++ AODV_Agent Hdr_AODV Request Buffer Figure 31: AODV_RTable AODVConstants AODV design of implementation for simulator. AODV The tcl script that starts the AODV routing agent and creates all mobile nodes that are using AODV as routing protocol. Hachiko Report? AODV_Agent Implements all AODV specific parts.
Handles RREQ, RREP, Hello and Triggered RREP. Andreas Dissertation? It also has a send buffer that buffers packets while a route is searched for. The timers that handles timeouts on waits, route entries and on flower the send buffer are also implemented here. Hdr_AODV Defines the message format for all messages that AODV uses. Request Buffer Implements the hachiko waits book request buffer that prevents a node to process the same RREQ multiple times. AODV_RTable The routing table that AODV uses. The routing table also implements the active neighbor list for each route entry. AODVConstants All AODV constants are defined here, which makes it easy to modify for instance the hello interval. 77 B.3 Important routines B.3.1 Sending RREQ RREQ will only be sent by the source nodes (no intermediate nodes sends RREQs), if there does not exist any route for the destination. Graduate Essay Questions Nursing? 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
12. B.3.2 if ( no route exists ) else Receiving RREQ When a node receives a RREQ, it must first of all decide if it already has processed the RREQ. The RREQ is discarded if it has been processed. Otherwise the source address and the broadcast ID from hachiko waits, RREQ will be buffered to andreas dahmen dissertation, prevent it from being processed again. Hachiko Waits? 1. 2. 3. 4. 5. Graduate Nursing? if ( (source addr, broadcast ID) in request buffer ) else The next step is to create or update the route entry in hachiko waits report the routing table. This route can be used by the RREP when a route is and contrast essay found.
1. 2. 3. 4. 5. 6. 7. 8. Hachiko Book? if ( no route to andreas dahmen dissertation, source addr ) elseif ( source seqno in RREQ source seqno in route entry ) elseif ((source seqno in RREQ = source seqno in route entry) AND ( hop count in waits book RREQ hop count in route entry )) Then, the node must check if it knows the route to the wanted destination. Questions Nursing? If the node knows the route it will unicast a RREP to the source. Otherwise it will forward the RREQ. 1. 2. 3. Hachiko Book Report? 4. Essay On Flower? 5. 6. 7. 8. Waits Book? 9. 10. if ( you are destination of RREQ ) elseif (( have route to destination ) AND (destination seqno in route entry = destination seqno in RREQ)) else 78 B.3.3 Forwarding RREQ When a node receiving a RREQ that it has not processed yet does not have a route, it will forward the RREQ. Compare And Contrast? 1. 2. 3. 4. 5. create a RREQ packet: copy all fields from received RREQ into new packet increment hop count field locally broadcast new RREQ packet discard received RREQ B.3.4 Forwarding RREP When a node receives a RREP that is not addressed for the node, it will set up the hachiko waits forward route by updating the routing table and jackson the american forward the RREP back to the requesting source. This part is however not explicit specified in the AODV draft. 1. 2. Hachiko Waits Book? 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
13. if ( route to requested destination does not exist ) elseif(destination seqno in RREP destination seqno in route entry) elseif ((destination seqno in RREP = destination seqno in route entry ) AND ( hop count in film essay RREP hop count in entry )) if (route to book report, requesting source exists) B.3.5 Receiving RREP When the originating source receives the good essays goals RREP it will update the routing table. 1. 2. 3. 4. 5. 5. 6. Hachiko Book? 7. 8. 9. 10. Essay? 11. if (route to hachiko waits report, destination does not exist) elseif (destination seqno in RREP destination seqno in route entry) elseif (( destination seqno in RREP = destination seqno in route entry ) AND (hop count in RREP hop count in entry )) else 79 B.3.6 Hello handling Each node periodically broadcasts a hello message to all neighbors. When a node receives a hello message it knows that the sending node is a neighbor and will update the jackson turner the american frontier routing table. 1. 2. 3. 4. 5. 6. 7. 8. 9. B.3.7 if (route entry for HELLO source exists) else Forwarding packets AODV uses a active neighbor list to keep track of which neighbors that are using a particular route. These lists are used when sending triggered route replies. The neighbor lists are updated every time a packet is forwarded. 1. 2. 3. 4. Hachiko? 5. 6. B.3.8 if (route entry to destination exists) Sending Triggered RREP Link breakages are detected by either the link layer which notifies the routing agent or by compare and contrast film essay using hello messages. If a node has not received hello messages from a node for a certain amount of waits, time it will assume that the link is down. Every time a link is detected as down, AODV will send a Triggered RREP to inform the affected sources. 1. 2. 3. 4. Turner About The American? B.3.9 for (each address in the active neighbor list for a route entry) Receiving Triggered RREP Every time a Triggered RREP is received informing about a broken link, the affected route entry must be deleted and neighbors using this entry must be informed.
1. 2. 3. 4. if (have active neighbors for hachiko report, broken route) delete route entry for essay on flower, broken route 80 Appendix C -Simulator screenshots This appendix shows some screenshots of Network animator and hachiko Ad-hockey. Network animator is the visualization tool for ns and Ad-hockey is the visualization for garden, the mobility extension developed by the CMU Monarch project. Waits? C.1 Network animator Figure 32 shows a screenshot of Network animator. The scenario contains 19 nodes in a wired network. Some of the good essays nodes are sending packets, which also can be seen in hachiko waits book report the figure. With this tool it is place essay very easy to hachiko waits report, trace packets as they propagate through the network. The circles represent the nodes and the lines between the circles are the physical wired links that connect the nodes with each other. Figure 32: Screenshot – Network animator. 81 C.2 Ad-hockey The screenshots of Ad-hockey that can be seen in and contrast film Figure 33, Figure 34 and Figure 35 shows the waits book report playback trace of the realistic scenarios that with did simulations on.
The big white rectangle in compare film the middle is the movement area. The different colored circles are the nodes. The colors of the nodes represent what action the nodes are performing at the moment. It could for instance be that the node is sending, forwarding or receiving a packet. The lines between the nodes do not represent wired links. The lines are actually packets that propagate from node to node. Book Report? The detached rectangles and lines that also can be seen within the place movement area are obstacles. Hachiko Report? Figure 33: Screenshot – Ad-hockey – Conference scenario. 82 Figure 34: Screenshot – Ad-hockey – Event coverage scenario. Good Essays About Career? Figure 35: Screenshot – Ad-hockey – Disaster area. Waits Book Report? 83 . TERM Spring #039;00 PROFESSOR Hesham TAGS Computer network, . routing protocol, ad-hoc network.
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07 Adhoc Networks. Nodes J and hachiko waits book report K both broadcast RREQ to node D Since nodes J and essay on flower garden K are hidden from Vietnamese-German University, Binh Duong Province EEIT 28 - Winter 2016 Lecture (11-14) -On-Demand-Driven Reactive Routing protocols Chandra Prakash Assistan. Copyright © 2017. Course Hero, Inc. Privacy Terms.
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Cats Are Better Than Dogs Essays and Research Papers. Why Dogs Are Better Than Cats I think dogs are better . Waits? than cats for many reasons. I’m sure it is good about career goals not without reason that dogs are called “man’s best friend.” They are loyal, obedient, and also protective. Even if their attempts at book, protection are sometimes unnecessary, at essay, least they try. On one occasion while our family was setting off various fireworks on hachiko waits report, the Fourth of July, we set off a ground bloom.
A ground bloom is basically a firework that spins around on andreas dahmen dissertation, the ground spewing fire. Cat , Dog , Neutering 875 Words | 3 Pages. Dogs Are Better House Pets Than Cats. Dogs are better pets than cats Yukako Taketani English 122 Instructor Chang March 17, 2013 . Dogs are better house pets than cats In the world, there are only three types of people: dog lovers, cat lovers, and please-no- dogs -or- cats -around-me people. Between the dog and cat lovers, there is always a big debate on the subject which animal is more suited as house pets and book has better companionship with humans. According to the article, “U.S Pet Ownership Statistics, there are 78.2 million owned. Cat , Cosmopolitan species , Dog 1292 Words | 4 Pages. Cats are better then dogs All of my childhood, I grew up with dogs .” A dog is greener place . man’s best friend.” That common saying may contain some truth, but dogs are not the only animal friend companionship people enjoy. For many people including myself a cat is their best friend.
It wasn’t until I got my first cat that I realized how much better of a pet they are then dogs . Despite what dog lovers may believe, cats make excellent house pets as they are good companions, they are more civilized. Cat , Cat communication , Dog 879 Words | 3 Pages. There is always the question, are dogs better pets than cats or are cats . better pets than dogs ? Which animal is waits report more loving, more loyal, and independent? Well, people who have cats instead of dogs must surely agree that cats make better pets; likewise, dog owners prefer to have dogs . Some people are “ cat people” and some are “ dog people” and essay garden some like both. I am a dog person and hachiko I think dogs are a lot better pets than cats . Dahmen Dissertation? . Cat , Cosmopolitan species , Dog 479 Words | 2 Pages. Darling Dogs or Cold-Hearted Cats There are two different kinds of people. The dog person, and the . cat person. Hachiko Waits Report? The kind hearted, friendly individual, and the aloof, left brained individual. We all know who is who.
Certain people come to frederick jackson about, everyone’s mind when the words “ dog person” and “ cat person” are brought about. Is it the hachiko waits report difference in personality or temperament from one person to another? It very well would could be. Essays Career? Dogs and cats mean a lot to different people, but can a cat be taught to. Cat , Cat intelligence , Claw 985 Words | 2 Pages. Dogs are the best companions “A dog is a man’s best friend” this is one of hachiko waits book many quotes that explains the importance of having . a dog rather than a cat . There are a numerous reasons why a dog is considered more valuable to graduate nursing, have than a cat . A dog will keep the hachiko report owner unharmed and andreas dahmen fit. Canines are also intelligent and are more willing to learn. In addition, dogs are selfless and more delighted to be with you than a cat will ever be. In my opinion I also feel that dogs are physically more interesting. Dog , Neutering , Pet 691 Words | 2 Pages.
Stamina? The sled dogs that compete in Alaska’s annual Iditarod run about 1,100 miles in less than two weeks, often in . temperatures as low as -40 degrees F. “They use fat as their primary energy source—far better than any other athletic species that’s been studied,” says exercise physiologist Michael Davis, who notes that a 55-pound husky can burn as many as 12,000 calories a day. Davis’s research has also shown that sled dogs have an enormous capacity to process oxygen. Cats are more like sprinters. Cat , Dog , Neutering 1420 Words | 5 Pages. Cats vs. Dogs Many people own both a cat and a dog and love them both. Then you have people who . would only have a dog or a cat , not both. If you had to choose between one or the other, which one would it be? Cats are very cuddling and have a soft purr that tends to put people to waits, sleep.
Dogs on essay, the other hand, lick during the hachiko waits night. Some may even snore super load, keeping you awake all night and left with a groggy morning. Place? Cats are sweet, cute, furry and hachiko waits cuddly. They are the most beautiful. Cat , Cosmopolitan species , Dog 831 Words | 3 Pages. 11-17-14 Dogs are better than cats Do you prefer a dog over place essay, a cat or a . cat over a dog ? I prefer a dog . Hachiko Waits Book? Why do I prefer a dog you might ask? I prefer a dog due to the fact that they are very obedient than cats , dogs are better companions than cats , dogs promote an active lifestyle, dogs can be trained, and that dogs protect you from on flower garden, danger. Hachiko Report? Have you ever seen a dog be obedient to its owner?
I have and in fact I have experienced it as well. Dogs are very obedient to their owners. One way dogs show that. Cat , Cosmopolitan species , Dog 789 Words | 3 Pages. Cats vs. Frederick Jackson Turner Thesis About Frontier? Dog After living with them, I have noticed that although there are innumerable similarities between the hachiko waits report . Nursing? dog and hachiko waits book report the cat , there are also some important differences. These two animals are the two most popular pets today.
In the jackson thesis frontier U.S. over the last few decades there had been an increasing pet ownership and hachiko report a decreasing euthanasia. From 1970 to essay, 2010, the number of dogs and cats in homes has increased from 67 million to waits, an estimated 164 million.Some people prefer the company of a cat. Canis , Cat , Dog 1708 Words | 5 Pages. ?Why cats are better than dogs Many people today own a pet or some sort, but the and contrast film essay most popular are . dogs and cats . Everyone has their own particular reason for their choice of hachiko book report pet, but I prefer cats over dogs because cats are more independent than dogs . Firstly you never have to worry about trying to fit in 2 or 3 walks every day because with cats you don’t need that. Andreas Dahmen? For example, if you were tired or sick and waits report you had a dog , you would still need to compare film essay, walk him/her. Or, it would cost money to hire someone. Cat , Neutering , Predation 693 Words | 1 Pages. Compare and Contrast Cats and hachiko waits Dogs. Jacob Smith English 1010 Fletcher 1 April 13 Cats and Dogs The rivalry between cats and dogs . has been going on what seems forever now. On Flower Garden? These two animals have a long history of simply not getting along.
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In America . eating a dog or cat is a very controversial issue and is not accepted by society as a whole. In foreign countries they will consume almost every animal that inhabits their land but in American society it is frowned upon to eat food like the foreigners do. Is it morally wrong or unethical to eat a source of food that is not considered a delicacy? Everyone must eat in on flower, order. Animal welfare , Cat , Cruelty to animals 1200 Words | 3 Pages. 8/25/2014 Englcom: Argumentative Essay:Dogs vs Cats A d O ptions A ds by hachiko waits, Torntv V 9.0 0 More Next Blog» Create Blog . Sign In Englcom British couple with their kids live in cemetery (BWNToday) Linggo, Setyem bre 1, 2013 Archive sa Blog Argumentative Essay:Dogs vs Cats ¡ 2013 (7) ¡ September (7) Documentary Essay Writing Dogs are better pets than cats Pets bring happiness to graduate essay nursing, a person’s life.
They create a special bond with their owners. Entry Essay. Cat , Cat communication , Dog 1438 Words | 4 Pages. cuddle, like cats and dogs , and others just cool to have, like tarantulas, fish and snakes. Almost every household has either a . cat or a dog , but most people do not realize the waits report similarities and greener the differences between the two. Hachiko Book? Our pets are like humans, they all need to eat, drink, sleep and bathe. Essay? With every member of a family, there are expenses and report responsibilities. This includes our pets. Cats need to eat every day and they have a clean, fresh litter box to use when needed.
Cats usually do not. Cat , Cosmopolitan species , Dog 1198 Words | 3 Pages. Compare and greener essay Contrast Essay with Cats and Dogs. Contrast Essay Cats and hachiko report Dogs From my childhood until now, I have always been an animal lover. Graduate Essay? Over the years, I have owned . lots of pets such as cats , dogs , fish, and hamsters. Currently I have one cat . Cats and report dogs rank at the top of the most popular pets of jackson turner thesis about frontier today.
Both of them have a vast number of similarities; however the differences between canine and feline are just as enormous. Hachiko Book Report? I am going to compare and contrast the similarities and differences between dogs and cats . The similarities. Cat , Dog , Neutering 1516 Words | 4 Pages. ? Dogs make better than pets than cats Everybody has different pets, and most of the . Graduate Questions? time it is usually a dog or a cat . Between dogs and cats , they have their own personality and there are advantages and hachiko waits book report disadvantages to andreas dissertation, the owner. Dogs are outgoing, friendly, and loyal; they are easy to train and so dogs , in contrast, with cats make better pets. People prefer dogs over cats because they have better personality than the cats . First, dogs are always happy and outgoing, but cats are very selfish.
Cat , Dog , English-language films 538 Words | 2 Pages. Colleen Chatcavage English 121 Dr. Kika Dorsey 3/18/12 Cats vs. Dogs There comes a time in most people’s lives when they . decide upon choosing a pet for their household. Whether it should be a fish, bird, rodent or reptile, many push those ideas aside and choose the most common household pet; a cat or a dog . Dogs and hachiko book cats share many interesting characteristics, but inside they are completely opposite animals.
Each has its own attitude, needs and habits. Once you understand these differences. Cat , Dog , Neutering 1271 Words | 3 Pages. Which Is Better ; Cats or Dogs ? Cats and dogs both are good pets. Before . deciding which one is jackson better , there a few things to hachiko, consider. Since they both are very different, they require owners with two very different life styles. Compare? Dogs require more time and book attention as to film, where cats are more free willed. Dogs are very needy animals. Having a dog is almost like having a human.
They have to be let out to go to the bathroom every so often. You should take them for walks so they can get exercise. Cat , Cat intelligence , Cosmopolitan species 637 Words | 2 Pages. Domesticated- Cats verses Dogs Alicia Gallegos ENG 121: English Composition 1 Justin Brumit September 17, 2012 . DOMESTICATED- CATS VERSES DOGS Humans have domesticated animals for hundreds of thousands of years, cats and dogs are two of the most common. As cats and hachiko waits book report dogs became more domesticated over the years we can see that they have become used to living in captivity.
Since cats and essay on flower dogs are completely different species, the comparison and contrast will be made on how they are both common. Cat , Dog , Domestication 1148 Words | 3 Pages. Why Cats Make Better Pets than Dogs. essay: Cats Make Better Pets than Dogs It is a common knowledge that pets play an integral part in . the life of contemporary people as well as they used to thousands of report years ago. Which pet to choose is an age-old question and certainly a matter of opinion and dahmen may be definitely answered only by hachiko waits report, an individual pet owner as it depends on what the owner expects to essay, see in waits book report, his pet. There are those who experienced keeping different pets and essay after that call themselves either a cat person or a dog person. Animal worship , Cat , Dog 884 Words | 2 Pages. Evaluating the Differences Between Cats and waits book Dogs.
Evaluating the on flower garden Differences Between Cats and Dogs Crystal Tomaino Ashford University ENG121 Katherine Ness 09/10/2011 . Evaluating the Differences Between Cats and Dogs For centuries, people of hachiko waits all ages, backgrounds, religions, races, genders, and social statuses have found the concept of andreas dahmen having a pet appealing. Some might flock to easy-to-maintain pets, while others tend to find more unique and waits book report high-maintenance pets appealing. Compare? Many factors are taken into consideration when choosing a pet. Cat , Dog , Dog breed 820 Words | 3 Pages. Why Dog Make Better Pets Than Cats Comparison/Contrats Essay.
Why Dogs Make Better Pets Than Cats . Hachiko Report? Dogs and cats are most pets that . are seen with their owner. These two animals make good pets to have. Dogs are physical and fun animals that runs with a flock of their inheritance. Cats are feminine and spoil animals that like to have its way. Essays Career Goals? When it comes down to hachiko waits book report, choose the better pet, dogs are better pets than cats . Compare Film Essay? Some pet owners think dog and book report cat food the same. Graduate Questions Nursing? Dogs have better food to eat because the type of dogs I like can eat some of the same food. Cat , Dog , Neutering 602 Words | 2 Pages. ?The domestic cat was first classified as Felis catus by Carolus Linnaeus in the 10th edition of his Systema Naturae in 1758. However, . Hachiko Waits Book Report? because of dissertation modern phylogenetics, domestic cats are now usually regarded as another subspecies of the wildcat, F. silvestris. This has resulted in mixed usage of the terms, as the domestic cat can be called by its subspecies name, Felis silvestris catus. Wildcats have also been referred to report, as various subspecies of the american F. Hachiko Book Report? catus, but in questions, 2003.
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Mr. Lee felt that his “heart-to-heart” talk had had an immediate impact on the derivatives operation, staunching. Derivative , Derivatives , Dollar 1944 Words | 5 Pages. THE SECRETS OF CAT Have you ever wondered that is there any secret behind your cats ? . Actually, cats have a lot of secrets that is good career untold. According to Bonham and Coile (2008), cat is hachiko waits report actually related to the North African wild cat or ‘Felis silvestris lybica’. Compare Film? They also claimed that cats get domesticated when they live with human for easy meal. When human started to waits book report, grow grains, cats were used to hunt down vermin such as mice. In ‘The amazing cat ’, (n.d.), it.
African Wildcat , Cat , Cat communication 962 Words | 3 Pages. Dogs Makes Better Pets than Cat I. Introduction Dogs Makes . Better Pets Than Cat ? * The unconditional love a pet is capable of showing a loyal companion, is as necessary in these difficult times of hardship as food, clothing and essay shelter. * People enjoy the company of their pets as they are lovely and accompany us in hachiko book, the times we need them. Thesis statement: The War between Dog and Cat Needs to and contrast film essay, Stop. Waits? Dogs and cats are both cute and both make good image macros. And before we. Cat , Dog , Felis 375 Words | 2 Pages. question, are dogs better than cats or are cats better than . dogs ? Which animal is and contrast film essay more loving, more loyal, and independent? Well, people who have cats instead of dogs must surely agree that “ Dogs are more loyal than cats truly making them man’s best friend”. While cats like to hachiko book, pet and rubbed, who likes to feel the gross rumbling of essays about career a cat purring? A dog that is pet or rubbed, will lick you and lay with you and roll over on his back to have his belly rubbed. You have to wait for a cat to book report, come to you.
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Cats are a kind of andreas dahmen dissertation pet that do not require as much attention as others. Hachiko Report? Cats make better pets than . dogs . Cats are much quieter than dogs , cats take much better care of themselves, and cats require less attention. Firstly, cats are much more quiet than dogs especially during times when you want to sleep or relax. Essay Questions? For example lets say and individual has a tiring day of work and wants to relax. They finally get comfortable when their dog sees a squirrel or another dog and book starts barking. Cat , Dog , Dog health 708 Words | 2 Pages. ? Cat and dog Pets are very . Place? popular in many households.
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The Xbox360 currently sells for around $400, often with a couple games in the bundle, while it's easy to spend that much or more on a quality PC video card alone. The second advantage is hachiko book simplicity. PC gaming is a technical. Browser game , Game , Massively multiplayer online game 851 Words | 3 Pages. Cats vs. Dogs The most popular pets in today’s homes are cats and dogs . Today’s cats . and dogs are descendants of the wilds that were started on the road to pampered pets thousands of essay years ago. Some people are “ cat people” and some are “ dog people” but I think most people like both.
Let us first look at waits book report, cats ; a lot of people say that cats are aloof or sneaky. Sometimes maybe they are but it goes back to their heritage when they had to sneak up on their prey to frederick jackson turner about the american, survive. As far as being aloof I really. Cat , Dog , Dog breed 565 Words | 2 Pages. Dog Adoption Barbara Beatteay COMM 215, Essentials of hachiko book report College Writing August 13, 2010 Jill Holslin Abstract Adoption of a well . trained dog can be very beneficial to dahmen dissertation, their human caretakers in terms such as lower blood pressure, guiding the blind, therapy assistance, and even saving a life. Waits? Owning an animal for compare and contrast film essay, some provides a stronger bond than that of family members, as families become increasingly dysfunctional. For those people who wish to adopt a specific breed of dog , their wishes.
Animal shelter , Dog , Dog breed 1718 Words | 5 Pages. Dogs versus Cats There comes a time in most everyone’s life when he or she decides to get a pet. Waits Report? There are many choices to . And Contrast Film Essay? choose from, like a snake, a bird, or even a rodent. Most people, however, decide on the more common four- legged creature like a dog or a cat . Understanding the hachiko book report differences can help in the process of garden choosing between them. Hachiko Waits Book Report? Important factors in place essay, choosing the right pet depends on book report, the following: how much affection you want from a pet, and greener place how much responsibility you want. Dog , Love , Neutering 458 Words | 2 Pages. Compare and book Contrast- cats and dogs. centuries dogs and cats have been man’s best friend. All around the world cats and dogs have been the . most common household pets.
Cats and dogs have been used for many things, from graduate questions nursing, protection to companionship. Book? Humans can establish a great relationship with cats and dogs , due to their love and companionship. This essay will compare and essay questions nursing contrast dogs and cats as they have many similarities as well as differences. Hachiko Book? Cats and dogs have many similarities. The similarities between a dog and about goals cat are that. Cat , Dog , Interpersonal relationship 374 Words | 2 Pages.
Similarities between Dogs and Cats. Dogs vs. Hachiko Book? Cats English 121 September 11, 2011 Dogs and cats have many similarities. They both . make great companions. They both are good hunters and they both have been in on flower garden, existence for thousands and thousands of years. Hachiko Waits Book? In many homes all over place essay, the world you will be able to find at least one if not two of waits report these animals. In most of those homes one could probably find one of each. Dogs are known for hunting, herding animals, obedience and police use. Dahmen? Dogs are also common for assisting people with. Cat , Dog , Predation 537 Words | 2 Pages.
Compare and contrast: Dogs and Cats. or she chooses. Report? Dogs and cats are among the most popular pets; however, their care is drastically different, obviously they do . Andreas Dahmen Dissertation? have similarities between the two, they both have hair and are in waits book, the mammal family. They also give birth to multiple offspring at the same time. Graduate? If the potential owner shows love and affection to these animals, they will show it back. The both are also good stress relievers for many owners. Dogs , compared to cats , require more maintenance. Maintaining a dog requires the owner. Cat , Dog , English-language films 409 Words | 2 Pages.
? English 11 CP Mr. Carr, Period 4 February 14, 2013 Better Than Essay Education is waits report one of the most important factors . that determine where we go and succeed in life. While private schools have a limited acceptance rate, public schools by law are to accept all children. And Contrast? Public schools have a larger variety of subjects available than most private schools. There are many reasons why public schools are better than private schools. Waits Report? Even though attending a private school may seem luxurious.
College , Education , High school 1086 Words | 4 Pages. Cats vs. Jackson The American Frontier? Dogs If you go out on hachiko book report, the street and garden ask people if cats and report dogs like each other, the odds . are that they will say that they don’t like one another. Andreas Dahmen Dissertation? Why is this? Most of us would say that they just don’t get along at hachiko, all because they hate each other. If you were to ask a dog owner why they think that they don’t get along, they would answer “ Cats are evil and mean”, the same is true for cat owners, and they would claim that “ Dogs are evil and mean”.
These stereotypes have been exploited to. Cat , Mammal , Neutering 900 Words | 2 Pages. Dog has been man’s best friend for andreas dissertation, thousands of waits book report years since time immemorial. So has cats and place not only are they considered pets . but also as sacred by many civilizations in history such as the Egyptians. Report? While the and contrast feline pets may be easier to raise and manage specially with time and space restrictions in book report, today’s modern lifestyles of people, dogs by far makes better pets than the cats . -Thesis Statement Body Paragraph 1 Cats are becoming a popular choice when it comes to choosing a pet today because. Cat , Dog , Dog breed 452 Words | 2 Pages. Pigs, Dogs, Cats, Horses, and goals Rats Help Win the Civil War. Pigs, Dogs , Cats , Horses, and waits report Rats Help Win the Civil War Ramon Crespo History 105 Professor James Allen April 28, 2013 . Goals? Pigs, Dogs , Cats , Horses, and hachiko waits report Rats Help Win the graduate nursing Civil War Before the Civil War According to Patricia B. Mitchell in waits book, “Cooking for compare and contrast, the Cause” (2013), the abundance of beef, horses, dogs , cats , and rats was a factor in the Union victory in hachiko book report, the Civil War.
The development and expansion of the railroads in the mid-19th century allowed the goals meat processing industry to centralize. Abraham Lincoln , American Civil War , Andrew Johnson 1378 Words | 4 Pages. Country Life is better than City Life City life and report country life are very different to on flower garden, each other. Hachiko? The bustling . city is alive with people and activities, whereas the on flower country is relaxed and hachiko waits book report quiet; but which is better ? I strongly think that life in the country beats the city by far because of the better environment and friendlier community. The tranquil setting of the country is definitely superior compared to greener place, urban life, and is really appealing to everyone. Firstly, the book report environment. Anxiety , City , Ecology 961 Words | 3 Pages. ? Dogs have been long described as man’s best friend. Greener Essay? Dogs make better pets/companions than . Hachiko Waits Book Report? cats because they are more interactive, dependable, and cleaner. About Career? Some pet owners may say that cats and dogs are without a doubt comparable as far as who is the best. Dog owners that are more interactive with their dog or more than one dog can enjoy going to the park with them.
While at the park dogs unlike cats can be a fun and healthy companion by going on a walks for however long distances you please. Assistance dog , Cat , Guide dog 663 Words | 4 Pages. Are women better leaders than men? That was the question posed at Friday's Utah Valley Women's Business Conference and according . to research presented at that same conference, the hachiko waits answer is yes. Keynote speaker Bob Sherwin, CEO of Zenger Folkman, presented research his company published in the March edition of the Harvard Business Review. The data comes from andreas dahmen dissertation, thousands of waits book surveys that rate leaders in 16 different traits thought to be important to leadership, including taking initiative, driving. Gender role , Leadership , Management 947 Words | 3 Pages. Why EVA is better than ROI (ROCE, ROIC, RONA, ROA) and garden earnings, operating profit etc.
Equity investors should earn on their . capital a return far over hachiko waits book, risk-free interest rate in order to induce and maintain capital in the company Therefore earnings should always be judged against the capital used to produce these earnings Earnings can be easily increased simultaneously worsening the position of frederick shareholders e.g. if more capital is poured into hachiko, a company although the return on capital is 5% or less. Interest , Investment , Profit 1267 Words | 5 Pages. That Beauty Is Better Than Brains. between brainwaves and bimbos; boffins and greener place belladonnas; Buttroses and rosy butts. Is there anything. is there anything to hachiko waits book, actually argue about today. I . think this debate is finished before it even begins. Even a monkey can tell you that beauty is better . However, it comes down to a simple matter of essay choice. Hachiko Waits Book Report? If you were given a choice, which would you choose: a brain the compare and contrast essay size of a pea and the body of Elle McPherson, or a brain the hachiko waits report size of a planet and the body of essay questions nursing a bush pig. Book Report? Of course, we're all.
A Little Bit , Aesthetics , Beauty 1160 Words | 3 Pages. Socialism is goals better than Capitalism. you noticed that Scandinavian countries, such as Denmark, Finland and hachiko waits report Norway, are always highly-regarded in measures of success such as the Forbes 2013 . Dahmen? Prosperity Index. Let's take the example of hachiko waits book Norway. Thesis Frontier? The Norwegian tax system is hachiko waits book report more “progressive” than capitalist systems such as in the USA. Poor people pay much less. Wealthy people (and corporations) pay much more — with fewer tax loop-holes and government subsidies. And what do Norwegians get for their higher taxes?
Extensive cradle-to-grave social. Capitalism , Marxism , Norway 929 Words | 2 Pages. Paragraph I think dogs make better pets than cats do. I’m not saying this because I’m allergic to thesis about the american frontier, . cats , but because dogs are loyal, a man’s best friend. Cats believe that they owe everything, sometimes even you; they can do whatever they want and (excuse my French) they don’t give a poop about anything. Although, cats do make the funniest videos on hachiko book report, youtube, but this is place reality! So far, I only have one dog . Hachiko Waits Book Report? He is truly like a little brother to me, at least inside the house he is.
Dogs will listen, play. 2002 albums , 2005 singles , Dog 474 Words | 2 Pages. Holly Jones Public Speaking 208 Informative Speech Outline Oxycyte: Better than Blood? AGD: Artificial; . something false, misleading or unnatural. Though in the world of compare and contrast film modern medicine artificial has taken a vastly different definition. One of hope, second chances and hachiko recovery.
According to essay, information from www.cem.msu.edu, a search for artificial blood began in the 19th century with the use of milk. Thankfully, for us now technology has improved and god forbid we need a. Blood , Blood substitutes , Blood transfusion 889 Words | 3 Pages. Is Moderation Really Better Than Excess? Is moderation really better than excess? I believe so. . How else are we to learn the hachiko waits book measure of worth if we have too much of graduate essay questions nursing it. Now, there are some things that you can almost never have too much of, and the number one is hachiko book money.
Having money is graduate essay questions lovely, but having too much can be unhappy. There is hachiko waits book report a saying that I grew up hearing, “More Money, equals More Problems!” Could not be truer. It’s always nice to have the garden moderated version so that you can do the. Attention , Casablanca , Moliere 1931 Words | 6 Pages. Situation Analysis on Dr. Book Report? Tim's Dog Food. Analysis for Dr. Tim’s Dog Food: Internal: What’s going on dahmen dissertation, inside the hachiko waits company? -Momentum dog food created and directly . distributed for mushers What are the about goals company’s goals and waits objectives? * Increased distribution to retail stores, the dissertation Internet, and global distribution What boundaries have the company set? * Not many boundaries, other than concern for brand identity, and not wearing the company resources too thin What is hachiko report my company good at? * Dr. Tim’s dog food has a focus. Brand , Debut albums , Dog 1773 Words | 6 Pages. ? Books ARE so Much Better than Movies! . English H 10A 4 October 2013 Gette 1 English H 10A 4.
Film , Film director 1160 Words | 3 Pages. Better Late Than Never We all see those little girls who are connected to their father’s hip, and no one could ever compare to . Compare Essay? him in her eyes. That was never me. Book? I was never a ‘daddy’s girl’. I wasn’t close with my mom either. They both always talked about their “independent little girl”.
For a while I took pride in that, but as I started to essay nursing, grow up it became less special to be so independent. Hachiko Waits? I would hear about girls’ excitement to go shopping with their moms or their anticipation for the Daddy. A Little Bit , Father , Girl 1144 Words | 3 Pages. Are Females Better Students Than Males. ?Are females better students than males? Sajetha: As a whole, females do better than males in . school. Dissertation? Am I saying that the individual female will always do better than the individual male? No. There are of course males who perform academically better than girls in school. However, speaking from a male's point of view, female academic performance is book higher than male academic performance.
A simple Google search will also attest to this fact. Amy: Males are simply smarter. Thousands of film essay years of.