17.1.5.1 DSDV

In this routing protocol routing messages are exchanged between neighbouring mobilenodes (i.e mobilenodes that are within range of one another). Routing updates may be triggered or routine. Updates are triggered in case a routing information from one of t he neighbours forces a change in the routing table. A packet for which the route to its destination is not known is cached while routing queries are sent out. The pkts are cached until route-replies are received from the destination. There is a maximum buffer size for caching the pkts waiting for routing information beyond which pkts are dropped.

All packets destined for the mobilenode are routed directly by the address dmux to its port dmux. The port dmux hands the packets to the respective destination agents. A port number of 255 is used to attach routing agent in mobilenodes. The mobilenodes al so use a default-target in their classifier (or address demux). In the event a target is not found for the destination in the classifier (which happens when the destination of the packet is not the mobilenode itself), the pkts are handed to the default-ta rget which is the routing agent. The routing agent assigns the next hop for the packet and sends it down to the link layer.

The routing protocol is mainly implemented in C++. See ~ns/dsdv directory and ~ns/tcl/mobility/dsdv.tcl for all procedures related to DSDV protocol implementation.