30.1.0.0.1 Preference Assignment and Control

Each protocol agent stores an array of route preferences, rtpref_. There is one element per destination, indexed by the node handle. The default preference values used by each protocol are derived from a class variable, preference_, for that protocol. The current defaults are:

        Agent/rtProto set preference_ 200               # global default preference;
        Agent/rtProto/Direct\footnote{Direct is a special routing strategy that is used in conjunction with Dynamic routing.  We will describe this in greater detail as part of the route architecture description.} set preference_ 100
        Agent/rtProto/DV set preference_ 120

A simulation script can control routing by altering the preference for routes in one of three ways: alter the preference for a specific route learned a particular protocol agent, alter the preference for all routes learned by the agent, or alter the class variables for the agent before the agent is created.