Repair Mechanisms

The agent will initiate a repair if it receives a request for a packet, and it does not have a request object pending_ for that packet. The default repair object belongs to the SRM/repair../ns-2/srm.tcl. Barring minor differences, the sequence of events and the instance procedures in this class are identical to those for SRM/request. Rather than outline every single procedure, we only outline the differences from those described earlier for a request object.

The repair object uses the repair parameters, D1_, D2_. A repair object does not repeatedly reschedule is timers; therefore, it does not use any of the backoff variables such as that used by a request object. The repair object ignores all requests for the same packet. The repair objet does not use the ignore_ variable that request objects use. The trace entries written by repair objects are marginally different; they are ``P NACK from requester'', ``P RTIMER at fireTime'', ``P SENDREP'', ``P REPAIR IGNORES holddown''.

Apart from these differences, the calling sequence for events in a repair object is similar to that of a request object.

Tom Henderson 2011-11-05