Saturday, 25 August 2012

Routing in NS2

The default routing protocol of NS2 is static routing. This means that there would be no change in topology throughout the simulation. In this case, NS2 configures the routing information once when the simulation start with the OTcl statement “$ns run”. The process proceeds as follows:

Step 1: [OTcl] Simulator::run
Step 2: [OTcl] Routelogic::configure
Step 3: [OTcl] Agent/rtProto/Static::init-all
Step 4: [OTcl] Simulator::compute-routes
Step 5: [OTcl] Simulator::computer-flat-route
Step 6: [OTcl] RouteLogic::compute
Step 7: [OTcl] Simulator::populate-flat-classifier

Step 6: The OTcl class RouteLogic is bound to the C++ class with the same name (see file ns-2.35/routing/,h). The OTcl command compute simply executes the funciton compute_routes(…) in the C++ domain. From this point, you have look closely of what NS2 does and apply necessary changes to fit your needs.

Step 7: See how NS2 populate the routing information to all the Nodes. You will need to look into this step to see how routing information are delivered to all related Nodes.