Visualizing Network Activities in NS with Reno simulation

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• The Network Animator (NAM) Tool
  
  • The Network Animator (nam) is a completely separate program that is distributed with the NS simulator
  • This program is named nam and it shows the progression of the packets through the network.
  • The nam program reads an input file (containing the packet transmission events) and draw the network events graphically.
• Running NAM
  
  • nam is a UNIX program and it is run as a command line.
  • Example:

    UNIX>> nam nam.input

    
    
    • nam.input is the file that contains network events
  • The key to making the animation input file is to tell NS to output network events into a file for nam to use. It's very simple...

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• Make NS output network event information for NAM
  
  • Do the following:
    
    1. Create an output file
    2. Activate the NAM trace feature in NS before running the simulation (this will tell NS to write NAM events outputs to the output file)
    3. Close output file at the end of the simulation run Then you can run nam with the output file (as input file for nam)
  • Here is an example of code in Tcl to achieve this:

    # (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)                                                
    
    • Prog file: click here
    Run the program using ns Reno1-nam.tcl; it will produce "out.nam" as output
    When it finishes, run: nam out.nam to see the packets flow.

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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...

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