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Visualizing Network Activities in NS with NAM

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• The Network Animator (NAM) Tool
  • The Network Animator (nam) Tool:

    NAM = a tool provided with the NS2 software to display the packets sent in a NS2 simulation

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• Running NAM
  • Syntax:

    UNIX>> nam nam.input

    nam.input is the file that is generate by the NS simulation

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• Generating NAM data in an NS simulation
  • Recipe to generate NAM data in a NS simulation:

    Open an output file Activate the NAM tracing the NS simulator object At the end of the simulation: Close the output file

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  • Tcl code to output NAM data:

    # (0) Creat a NS simulator object set ns [new Simulator] # (1) Create the trace file set namfile [open out.nam w] # (2) Tell NS to write NAM network events to this trace file $ns namtrace-all $namfile # (3) Close output file at the end of the simulation run proc finish {} { global ns namfile $ns flush-trace ;# flush trace files close $namfile ;# close trace file exec nam out.nam & ;# OPTIONAL: run NAM from inside the NS simulation exit 0 }

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  • Example Program: (Reno code with NAM)                                                

    cd /home/cs455000/demo/NS2/progs ns Reno1+nam.ns

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• Making a better animation
  • The output does not look very good...
    • The nodes and links are placed very awkwardly
    • All packets (from all flows) are colored black

  • We can change some parameters in the animation from inside NS !

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• Placing Nodes to make NAM animations look good
  • We can manipulate the placement of nodes through the $ns duplex-link-op (or $ns simplex-link-op) method on an existing link (to suggest a "direction"):
    • left, right
    • up, down
    • left-up, left-down
    • right-up, right-down

  • Examples:

    $ns duplex-link-op $n0 $n1 orient left	Make link n0-n1 orient to left
    $ns duplex-link-op $n0 $n1 orient left-down	Make link n0-n1 orient to left-down
    $ns duplex-link-op $n0 $n1 orient left-up	Make link n0-n1 orient to left-up
    $ns duplex-link-op $n0 $n1 orient right	Make link n0-n1 orient to right
    $ns duplex-link-op $n0 $n1 orient right-down	Make link n0-n1 orient to right-down
    $ns duplex-link-op $n0 $n1 orient right-up	Make link n0-n1 orient to right-up

  • NOTE: if things do not look good, you can press a "re-layout" button in NAM to make NAM re-arrange the nodes....

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  • Example Program: (Reno code with NAM - positioned nicely)                        
    • Prog file: click here

    Run the program using ns Reno1-nam-2.tcl; it will produce "out.nam" as output

    When it finishes, run: nam out.nam to see a nicer network animation

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• Coloring Packets from different sources
  • Each TCP (or UDP) agent has a built-in flow id variable named fid_

  • Each packet from a flow will have this given fid_ value.

  • You can assign a value to the fid_ of a TCP/UDP agent using the set command:

    $tcp1 set fid_ 234

  • You can "color" packets from a given TCP/UDP agent by assigning a color to a certain flow id value.

    For example, if you want packets that has fid_ = 234 colored blue, then use:

    $ns color 234 blue

    This set the color of the packets of flow 234 to blue. When NAM is run, these packets will be colored blue.

  • The different colors can highlight which packets are being dropped...

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  • Example Program: (Reno code with NAM - positioned nicely)                        
    • Prog file: click here

    Run the program using ns Reno1-nam-3.tcl; it will produce "out.nam" as output

    When it finishes, run: nam out.nam to see blue packets...