RFC 2092 (rfc2092) - Page 2 of 6

Protocol Analysis for Triggered RIP

RFC 2092            Triggered RIP Protocol Analysis         January 1997


   o  Point-to-point links supporting PPP link quality monitoring or
      echo request to determine link failure.

   A triggered RIP implementation runs standard RIP on Local Area
   Networks  (LANs) allowing them to interoperate transparently with
   implementations adhering to the original specifications.

3. Key Features

   The proposal shares the same basic algorithms as RIP or RIP-2 when
   running on LANs; Packet formats, broadcast frequency, triggered
   update operation and  database timeouts are all unmodified.

   The new features operate on WANs which use switched circuits on
   demand to achieve intermittent connectivity; Or on permanent WAN
   connections where there is a desire to keep routing packet overhead
   to a minimum.  Instead of using periodic 'broadcasts', information is
   only sent as triggered updates.  The proposal makes use of features
   of the underlying connection oriented service to provide feedback on
   connectivity.

3.1 Triggered Updates

   Updates are only sent on the WAN when an event changes the routing
   database.  Each update is retransmitted until acknowledged.
   Information received in an update is not timed out.

   The packet format of a RIP response is modified (with a different
   unique command field) to include sequence number information.  An
   acknowledgement packet is also defined.

3.2 Circuit Manager

   The circuit manager running below the IP network layer is responsible
   for establishing a circuit to the next hop router whenever there is
   data (or a routing update) to transfer.  After a period of inactivity
   the circuit will be closed by the circuit manager.

   If the circuit manager fails to make a connection a circuit down
   indication is sent to the routing application.  The circuit manager
   will then attempt at (increasing) intervals to establish a
   connection.   When successful a circuit up indication is sent to the
   routing application.








Sherry & Meyer               Informational