Network Simulator2

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

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Adding Nodes and Links

• To create a network node
• Set n0 ns node

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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 lttypegt
• lttypegtstatic,session,DV,cost,multi-path
• Multicast
• ns multicast
• ns mrtproto lttypegt
• lttypegtDM,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.