DMN1 : COMMUNICATION PROTOCOL SIMULATION. Faculty of Engineering Multimedia University

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1 DMN1 : COMMUNICATION PROTOCOL SIMULATION Faculty of Engineering Multimedia University DMN1 Marking Scheme No Component Criteria Not answered 0 marks Poor 2 marks Acceptable 4 (max) marks 1 Viva Students able to understand some questions related to the experiments 2 Report Report follow scientific format 3 Report The experiment is conducted thoroughly and result is well analyzed 4 Report The report provide good reasons and justifications to support the conclusion Total marks = 16 Lab 1 contributes 5% to the course work mark. 1.0 OBJECTIVES To understand and simulate network traffic using NS2 network simulator. To investigate and observe TCP and UDP protocols implemented in the transport layer. To study and analyse the different applications run over different transport layer protocols. 2.0 LIST OF EQUIPMENT AND SOFTWARE Computer running ns-allinone (latest release is 2.31) is a package which contains required components and some optional components used in running NS-2. The package contains an "install" script to automatically configure, compile and install these components. Currently the package contains: Tcl release (Main component) Tk release ( Main component) Otcl release 1.13 ( Main component) TclCL release 1.19 ( Main component) Ns release 2.31 (Main component) Nam (Animation purpose) Gnuplot (Plotting purpose) External storage (thumb drive brought by student) to save the simulation output. Download codes before come for lab experiment at the course page in MMLS. 3.0 LAB EXPECTATIONS Work on pre-experimental preparation. Answer pre-experimental questions. Work on the lab experiments. Record results and make analysis from the results experiment. Answer post-experimental questions. ETM4116 1

2 4.0 INTRODUCTION NS or the network simulator (also popularly called ns-2, in reference to its current generation) is a discrete event network simulator. NS-2 is popularly used in the simulation of routing and multicast protocols, among others, and is heavily used in ad-hoc networking research. NS-2 supports an array of popular network protocols, offering simulation results for wired and wireless networks alike. It can be also used as limited-functionality network emulator. It is popular in academia for its extensibility (due to its open source model) and plentiful online documentation. NS-2 is licensed for use under version 2 of the GNU General Public License. NS-2 consists of these modelling network components: Traffic models and applications o Web, FTP, telnet, audio, sensor networks Transport protocols o TCP (Reno, SACK, etc), UDP, multicast Routing and queuing o static routing, DV routing, multicast, ad-hoc routing o queuing disciplines: drop-tail, RED, FQ Link layer o wired, wireless, satellite It also provides useful infrastructure for tracing, visualization, error models, etc. Programmers can modify and create their own modules. For tracing proposes, user can extract the raw data from data file (example out.tr) From there raw data, graph for analysis can be executed as shown below: ETM4116 2

3 5.0 PRE-EXPERIMENTAL QUESTIONS 5.1 Name three other simulation tools commonly used for network simulation. 5.2 What is the difference between a.tcl file extension with a.nam file extension. 5.3 Explain the working of a sliding window flow control protocol. 6.0 EXPERIMENTS START RUNNING KNOPPIX For these experiments, we will be using Knoppix with embedded NS-2. Knoppix is complete Linux distribution that can run for a single CD. Usually this kind of distribution is called a live CD where it can load Linux system without installing it on a hard drive. The distribution used for this experiment come with NS-2 embedded in it. Hence, student can run the NS-2 without having to install it on the hard drive. Please get a Knoppix CD from the lab technician. Note: please insert your thumb drive onto the USB slots before run the Knoppix. Start using Knoppix After Knoppix uploaded, type the command below to run the KDE environment: startx Bring up the Console, and setup path for nam and xgraph line by line (press Enter after each line): sh-3.00# PATH= $PATH:/usr/local/ns-allinone-2.29/nam-1.11 sh-3.00# export PATH sh-3.00# PATH= $PATH:/usr/local/ns-allinone-2.29/xgraph-12.1 sh-3.00# export PATH To check either the paths are already set, type the commands below one by one. It should return the path to the required applications: sh-3.00# which ns sh-3.00# which nam sh-3.00# which xgraph To set your working path, type sh-3.00# cd Desktop From now on, save all the documents and files on your desktop. Eject and shutdown Knoppix At the end of session, after logout from the KDE environment, press the below keys simultaneously to eject the CD: Ctrl+Alt+Del ETM4116 3

4 6.1 EXPERIMENT Experiment1: Simple UDP Simulation Open the file name experiment1.tcl. Observe the code to understand a simple script for UDP simulation. Question 1: What is the name of the nam file created and what is the purpose of this nam file? Run experiment1a.tcl sh-3.00# ns experiment1.tcl Observation 1: Observe and note down your observation. Question 2: Can you name the application that is running in this experiment. Question 3: The UDP connection is running a CBR traffic. What is CBR stand for and give one application example that use CBR traffic? Question 4: Why are there packets drop in node0? Observation 2: Try changing the link bandwidth from 1Mbps to 1MBps. What is the different from from the previous execution? Explain your observation. Observation 3: Change the queuing policy Droptail at line 28 to FQ. Write your observation. (FQ stands for stochastic fair queuing.) Experiment2: TCP Simulation with Sliding Windows Protocol Run the experiment1b.tcl with the arguments below: ns experiment2.tcl <cong_window> <link_delay> sh-3.00# ns experiment2.tcl ms Observation 4: Observe the differences as compare to Experiment1. Observation 5: What do you observe every time the packet transmitted exceeded the link bandwidth capacity? Observation 6: What happen when you change the value of <cong_window> to 10, 50, 500 and 1000? Explain your observation Experiment3: TCP versus UDP Run the file experiment3.tcl with the link capacity as an argument: sh-3.00# ns experiment3.tcl 1MB Observation 7: Write down your observation. Question 5: What colour represent the TCP connection? How did you come to this conclusion? Observation 8: Try changing the argument values for example 1Mb. What do you observe? ETM4116 4

5 6.1.4 Experiment4: Sending FTP and CBR from different sources Manipulate the code given in experiment3.tcl to make it sending and receiving from different sources but sharing the same command link as shown in Figure 1. Give your new file name as experiment4.tcl. FTP Sender 1Mbps Link Capacity 1Mbps FTP Receiver CBR Sender 0.5Mbps Switch Switch 0.5Mbps CBR Receiver Figure 1 Show the instructor the successful animation. Observation 9: Comment on your observation. Plotting with XGRAPH We are going to use xgraph, a simple graph plotting tool, to help in our analysis. Xgraph read files that consist of 2 columns of data one column provides the x-axis data and the other column provides the y-axis data. To extract certain columns from NS2 trace file (e.g. outexperiment4.tr), we may use the following command: sh-3.00# awk {print $2, $12} trace.tr > plot.tr The above command will select data from column 2 and column 12 from file trace.tr and save it into new file plot.tr : To start plotting: sh-3.00# xgraph plot1.tr Question 6: What is awk? 7.0 POST-EXPERIMENTAL ANALYSIS AND DISCUSSIONS 7.1 How do you run the nam animator from command line? 7.2 What happen to the packets when the packets were dropped during transmission? 7.3 By using awk, write a script to extract the throughput performance of the FTP and CBR connections in Experiment 4. Comment on the throughput performance observed. 7.4 What can you conclude from these experiments? 8.0 REFERENCES [1] The Network Simulator - NS-2 (no date). Home page. [Online]. University of Michigan. [2007, June 11]. [2] NS Manual (no date). Home page. [Online]. University of Michigan. [2007, June 11]. [3] NS by Example (no date). Home page. [Online]. University of Michigan. [2007, June 11]. [4] Fred Halsall, Computer Networking and the Internet, 5th Edition, Addison Wesley; 2005 ETM4116 5

6 Appendix I How to Start Create an event scheduler set ns [new Simulator] Open a file for trace data set nf [open out.nam w] $ns namtrace-all $nf A procedure to close file and start NAM proc finish {} { global ns nf $ns flush-trace close $nf exec nam out.nam & exit 0 } Schedule the procedure $ns at 5.0 "finish" Start simulation $ns run Topology Node set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] Link $ns duplex-link $n0 $n1 1Mb 5ms DropTail $ns duplex-link $n1 $n2 400Kb 10ms DropTail Agent/Application Create a UDP agent and attach it to node n0 set udp [new Agent/UDP] $ns attach-agent $n0 $udp Create a CBR traffic source and attach it to udp0 set cbr [new Application/Traffic/CBR] $cbr attach-agent $udp Create a null agent to be traffic sink set null [new Agent/Null] $ns attach-agent $n2 $null Connect them $ns connect $udp $null Schedule the event $ns at 0.5 "$cbr start" $ns at 4.5 "$cbr stop" Create a FTP traffic source and attach it to udp0 set ftp [new Application/FTP] $ftp attach-agent $tcp Create a TCPSink agent to be traffic sink set sink [new Agent/TCPSink] $ns attach-agent $n2 $sink Connect them $ns connect $tcp $sink Schedule the event $ns at 0.5 "$ftp start" $ns at 4.5 "$ftp stop" Traces Traces in NS-2 format $ns trace-all [open tr.out w] <event> <time> <from> <to> <pkt> <size> -- <fid> <src> <dst> <seq> <attr> cbr cbr r cbr d cbr Traces in NAM format $ns namtrace-all [open tr.nam w] Turn on tracing on specific links $ns trace-queue $n0 $n1 $ns namtrace-queue $n0 $n1 Event and Queuing Schedule events $ns at <time> <event> <event>: any legitimate ns/tcl commands Links and queuing $ns duplex-link $n0 $n1 <bandwidth> <delay> <queue_type> <queue_type>: DropTail, RED, CBQ, FQ, SFQ, DRR Routing Unicast $ns rtproto <type> <type>: Static, Session, DV, cost, multi-path Multicast $ns multicast (right after [new Simulator]) or set ns [new Simulator multicast on] $ns mrtproto <type> <type>: CtrMcast, DM, ST, BST (centralized,dense mode, shared tree) Create a TCP agent and attach it to node n0 set tcp [new Agent/TCP] $ns attach-agent $n0 $tcp ETM4116 6

7 Traffic on top of UDP UDP set udp [new Agent/UDP] set null [new Agent/Null] $ns attach-agent $n0 $udp $ns attach-agent $n1 $null $ns connect $udp $null CBR set src [new Application/Traffic/CBR] Exponential or Pareto set src [new Application/Traffic/Exponential] set src [new Application/Traffic/Pareto] Traffic on Top of TCP TCP set tcp [new Agent/TCP] set tcpsink [new Agent/TCPSink] $ns attach-agent $n0 $tcp $ns attach-agent $n1 $tcpsink $ns connect $tcp $tcpsink FTP set ftp [new Application/FTP] $ftp attach-agent $tcp Telnet set telnet [new Application/Telnet] $telnet attach-agent $tcp ETM4116 7