BU CS 580S - AODV comparing to DSR as Example

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1 Design Routing Protocol Performance Comparison in NS2: AODV comparing to DSR as Example Yinfei Pan Department of Computer Science SUNY Binghamton Vestal Parkway East, Vestal, NY 13850 Abstract There are already many projects try to tell us how to use NS-2 easily, while not as that difficult as its official manual says. However, how to easily use NS-2 to do performance evaluation is still lacking. Usually, a trace file which comes out from one time NS-2 simulation is larger than 600MB, to analysis this huge file definitely will cost great time. Till now, there are many evaluation methods, but use them is very time cost and may not exactly what the simple version we want. This paper is to let people who use NS-2 can easily do the work of network post simulation. Thus make it easier and faster in making NS-2 more practical. Furthermore, this paper apply this performance evaluation method on the comparison of two on-demand source routing protocols AODV and DSR, and shows DSR is somewhat suitable for sensor work applications 1. Introduction Ns-2 is an object-oriented simulator developed as part of the VINT project at the University of California in Berkeley. The project is funded by DARPA in collaboration with XEROX Palo Alto Research Center (PARC) and Lawrence Berkeley National Laboratory (LBNL). Ns-2 is extensively used by the networking research community. It provides substantial support for simulation of TCP, routing, multicast protocols over wired and wireless (local and satellite) networks, etc. The simulator is event-driven and runs in a non-realtime fashion. It consists of C++ core methods and uses Tcl and Object Tcl shell as interface allowing the input file (simulation script) to describe the model to simulate. Users can define arbitrary network topologies composed of nodes, routers, links and shared media. A rich set of protocol objects can then be attached to nodes, usually as agents. It had already become the ”de facto” standard in networking research.[1, 2] Although NS is fairly to use once you get to know the simulator, it is quite difficult for a first time user, because there are few user-friendly manuals. Even though there is lots documentation written by the developers who has in depth explanation of simulator, it is written with the depth of a skilled NS user. There already are many user friendly tutorials to make how to use ns-2 easily [3, 4]. They give a new user some basic idea of how the simulator works, how to setup simulation networks, where to look for further information about network components in simulator codes, how to create new network components, and so on. They are mainly focus on simple examples and brief explanations. Although all the usage of the simulator or possible network simulation setups may not be covered in those projects, the projects also help a new user to get quick started. However, with this good tutorials material available today, there still lack documents to ease the analysis work of post-simulation. Since ns-2 is an academic project, the main purpose is for evaluating the existing network’s performance or the performance of network with new design of component [6, 7]. Thus, to make progress on this problem, this paper is to let people who use ns-2 can easily do the work of network post simulation analysis, which will further make ns-2 more practical on doing scalable simulation. In the rest of this paper, section 2 will discuss how to conduct a wireless simulation in ns-2; section 3 will describe about the trace file format of ns-2, and then section 4 will do analysis on two sample routing protocols, AODV and DSR, and also show how our performance evaluation mode can work on the analysis of them. 2. Wireless simulation in NS-2 2.1. Software structure and mechanism of NS-22 The key to get to know ns-2 is it is a discrete event network simulator. In ns-2 network physical activities are translated to events, events are queued and processed in the order of their scheduled occurrences. And the simulation time progresses with the events processed. And also the simulation “time” may not be the real life time as we “inputted”. But, why is ns-2 that useful, what kind of work can be done by ns-2, it can model essential network components, traffic models and applications. Typically, it can configure transport layer protocols, routing protocols, interface queues, and also link layer mechanisms. We can easily see that this software tool in fact could provide us a whole view of the network construction, meanwhile, it also maintain the flexibility for us to decide. Thus, just this one software can help us simulate nearly all parts of the network [1-5]. This definitely will save us great amount of cost invested on net work constructing. The following Figure 1 shows a layered structure which ns-2 can simulate for us. After the simulation finish, the way ns-2 used to present the most details information on that much network layer is that it provides us a huge trace file recording all the events line by line in it. So, now we see why event driven mechanism is used in ns-2, since it really could maintain the things ever happened as records. And we can trace these records to evaluate the performance of special stuffs in our network, such as routing protocol, Mac layer load, and so on. As Figure 2 shows, for the data flow of one time simulation in ns-2, the user input an OTcl source file, the OTcl script do the work of initiates an event scheduler, sets up the network topology using the network objects and the plumbing functions in the library, and tells traffic sources when to start and stop transmitting packets through the event scheduler. And then, this OTcl script file will be passed to ns-2, in this view, we can treat ns-2 as Object-oriented Tcl (OTcl) script interpreter that has a simulation event scheduler and network component object libraries, and network setup module libraries. And then the detail network construction and traffic simulation will be actually done in ns-2. After a simulation is finished, NS produces one or more text-based output files that contain detailed simulation data, and the data can be used for simulation analysis [3, 5]. From the NS-2 developer view, Figure 3 shows the layered architecture of ns. The event schedulers and most of the network components are implemented in C++ and available to Tcl Script, thus the lowest level of NS-2


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