1. Network Simulator-2 Sandeep singla 1998A2A7540

2. NS-2 A discrete event simulator Focused on modeling network protocols –Wired, wireless –TCP,UDP,unicast,multicast –Web,telnet,ftp –Routing protocols –Error modeling

3. Ns components Ns, the simulator itself Nam, Network animator –Visualize the ns output –GUI input the simple scenarios Preprocessing –Traffic and topology generator Post processing –Simple trace analysis,often in TCL

4. Languages Uses two languages –C++ for packet processing Fast to run,detailed,complete control –TCL for control Simulation setups,configuration,occasional events Fast to write and change

5. TCL The file has the extension.tcl. To start the first line is. –Set ns [new simulator]. –This will create a simulator object.

6. TCL Next a file is opened for dumping all the trace data to be used by nam (network animator). –Set nf [open out.Nam w]. – $Ns namtrace-all $nf.

7. TCL The next step is to add a finish procedure to close the trace file and start the nam. –Proc finish {} { Global ns nf $Ns flush-trace Close $nf Exec nam out.Nam & Exit 0 }

8. TCL The next step is to execute the finish procedure and then start the simulation. –$ns at 5.0 "finish" –$ns run

9. Adding Nodes and Links To create a network node –Set n0 [$ns node]

10. Adding Nodes and Links To create a link between two nodes –$Ns duplex-link $n0 $n1 1mb 10ms DropTail –Specifies bandwidth,delay,and queue type Drop tail,RED,CBQ,FQ,SFQ,DRR

11. Adding Nodes and Links To send data – Set udp0 [new agent/UDP] $Ns attach-agent $n0 $udp0 Set cbr0 [new application/traffic/CBR] Set null0 [new agent/null] $Ns attach-agent $n1 $null0 $Ns connect $udp0 $null0 $Ns at 0.5 "$cbr0 start" $Ns at 4.5 "$cbr0 stop"

12. Routing Alternatives Unicast –$ns rtproto – :static,session,DV,cost,multi-path Multicast –$ns multicast –$ns mrtproto – :DM,ST,BST,CtrMcast

13. What More Can Be Done.. Ns-2 offers a simulation of a variety of protocols ex: various routing protocols, various multicast and broadcast protocols. All the links can be monitored and graphs can be created of the traffic pattern using a tool that comes along with the ns-2 package- x graph.

14. What More Can Be Done.. Wireless networks can be simulated using ns-2 and various tools have been provided for this purpose. The various network failures scenarios can also be simulated, for example failure of a link or a node.