This section briefly describes the functionality of the dynamic source
routing protocol. As mentioned earlier the SRNode is different from
the MobileNode. The SRNode's entry
_ points to the DSR routing agent, thus forcing all packets received by the node to be handed down to the routing agent. This model is required for future implementation of piggy-backed routing information on data packets which otherwise would not flow through the routing agent.
The DSR agent checks every data packet for source-route information. It forwards the packet as per the routing information. Incase it doesnot find routing information in the packet, it provides the source route, if route is known, or caches the packet and sends out route queries if route to destination is not known. Routing queries, always triggered by a data packet with no route to its destination, are initially broadcast to all neighbours. Route-replies are send back either by intermediate nodes or the destination node, to the source, if it can find routing info for the destination in the route-query. It hands over all packets destined to itself to the port dmux. In SRNode the port number 255 points to a null agent since the packet has already been processed by the routing agent.
See ~ns/dsr directory and ~ns/tcl/mobility/dsr.tcl for implementation of DSR protocol.
Tom Henderson 2011-11-05