DIAMETER: Difference between failover and failback in the diameter protocol ?

Question

Failover and Fallback procedures we know very well.

Suppose initial message was supposed to send to primary peer, but peer went down and message has been forwarded to Secondary peer i.e. Failover. Now suppose if Primary Peer has come up and according to DIAMETER theory the message should go to primary peer. So the next message will be Update message. Which will have the same session id which was used with the initial message.

Now my doubt is how the primary peer will recognize the session-id of update message. Because it has no info for that session. The session was created with the secondary peer.

Answer 1

Failover and Fallback feature is not enable by default. We have to enable this feature and has to configure the Primary Peer and Secondary Peer for an Entity.

Failover: When a Primary Peer is not up (Primary Peer: Where the message was intended to reach or the actual destination) then the Pending messages will be forwarded to the Secondary Peer. This procedure is called Failover.

Fallback: After failover if the Primary Peer is again got up so the messages flow should again change towards the Primary peer. This procedure is called Fallback.

Note: It is only possible when the Destination Peer AVP is not present in the message.