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NS Programming

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• How to program simulation using NS2 ?
  • NS2 programs are programs written in the Object Tcl programming language

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• What is Tcl and OTcl ?
  • Tcl ("tickle") stands for "Tool Command Language" and is a scripting language created by John Ousterhout.

    Here is a page of Tcl in Wikipedia: click here

• Network Simulator NS and OTcl
  • The network simulator NS is actually an OTcl programming language interpreter with a built-in library of network simulation objects

    It is very useful to know how to program in OTcl to use NS.

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• Where is NS2 installed ?
  • The network simulator NS2 is installed on Emory's MathCS system.

  • Set up environment variables:

    If you are using ksh, you can gain access to the NS program by executing this command: /home/cs455000/bin/add-kshrc This shell script will add a path to your .kshrc file. If you are using bash, you need to run: /home/cs455000/bin/add-bashrc

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  • The /home/cs455000/bin directory will be added to your PATH variable when you run the add-kshrc or add-bashrc scripts.

  • You need to log out and log back in to activate the new path (or execute . ~/.kshrc (for ksh) or source ~/.profile (for bash))

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• How to run NS2
  • If you have added the correct path to your environment variable (using the above procedure, you should be able to run NS using the command line:

    ns2

  • You can also run NS directly using the command:
    /home/cs455000/bin/ns2

  • You will see a prompt:
    %

    and you can enter Object TCL programming commands.

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  • When you write simulation programs, you would NOT use NS interactively.

    You would first write an NS script (= program) using an editor

    Then you run the NS script using:

    ns NS-script-file