Network Simulator ns2

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Network Simulator ns2

• An introduction

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Computer based objects

• Ns2 uses C objects
• Objects possess
• Attributes
• - state variables
• Function or procedures
• - required to manipulate variables
• User creates instances of objects
• Features passed via inheritance

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Components of ns2

• To run ns2 enter
• ns2 ns-simple.tcl
• Network animator - nam
• Output file out.nam (typical)
• To run animator
• nam out.nam

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Setting up ns2 - 1

• To create a simulator object
• set ns new Simulator
• Define colors for data flows
• Used in nam - comment
• Blue Red Green Orange
• Grey Cyan Black Pink
• ns color 1 Blue

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Setting up ns2 - 2

• Open the NAM trace fileset nf open out.nam
  wns namtrace-all nf
• File variable nf
• Open nf for writing
• User defines name of output file - out.nam

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Setting up ns2 - 3

• Define a 'finish' procedure
• proc finish global ns nf ns
  flush-trace Close the NAM trace file
  close nf Execute NAM on the trace
  file exec nam out.nam exit 0

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Setting up ns2 - 4

• Create four nodesset n0 ns nodeset n1 ns
  nodeset n2 ns nodeset n3 ns nodeset n4
  ns node

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Setting up ns2 - 4

• Create links between the nodes
• ns duplex-link n0 n2 2Mb 10ms DropTail
• ns duplex-link n1 n2 2Mb 10ms DropTail
• ns duplex-link n2 n3 1.7Mb 20ms DropTail

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Setting up ns2 5

• Give node position (for NAM)
• ns duplex-link-op n0 n2 orient right-down
• ns duplex-link-op n1 n2 orient right-up
• ns duplex-link-op n2 n3 orient right

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Setting up ns2 6

• Set Queue Size of link (n2-n3) to 20
• ns queue-limit n2 n3 20
• ns queue-limit n3 n6 20

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Screenshot 1
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Setting up ns2 7

• Monitor the queue for link (n2-n3). (for NAM)
• ns duplex-link-op n2 n3 queuePos 0.5

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Setting up ns2 8

• Setup a TCP connectionset tcp new
  Agent/TCPtcp set class_ 2ns attach-agent n0
  tcpset sink new Agent/TCPSink

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Setting up ns2 9

• ns attach-agent n3 sinkns connect tcp
  sinktcp set fid_ 1
• Flow id fid sets colour

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Setting up ns2 10

• Setup a FTP over TCP connectionset ftp new
  Application/FTPftp attach-agent tcpftp set
  type_ FTP

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Setting up ns2 11

• Setup a UDP connectionset udp new
  Agent/UDPns attach-agent n1 udpset null
  new Agent/Null

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Setting up ns2 12

• ns attach-agent n3 nullns connect udp
  nulludp set fid_ 2

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Setting up ns2 13

• Constant bit rate CBR
• Setup a CBR over UDP connectionset cbr new
  Application/Traffic/CBRcbr attach-agent
  udpcbr set type_ CBRcbr set packet_size_
  1000cbr set rate_ 1mbcbr set random_ false

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Schedule events

• Schedule events for the CBR and FTP agentsns
  at 0.1 "cbr start"ns at 2.0 "ftp start"ns
  at 3.0 "ftp stop"ns at 5.0 "cbr stop"

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Run simulation

• Define time to detach agents
• Define time to call finish
• Print some parameters
• Run the simulationns run

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Screenshot