In theory, 100 should not be used with non-INVITE requests because they will always get responses promptly. In practice, in a lot of situations, non-INVITE requests will not get prompt responses, and there will be retransmissions that are not useful because the recipient of the retransmission has received the request already.
In our system, we've arranged that when an element receives an INVITE request, it sends a 100 response, and when an element receives the *second* copy of a non-INVITE request, it sends a 100 response. When an element receives a 100 response, it quenches any re-sending of the request. This has worked well in all situations for us. The one absolute rule is that an element may send a 100 response ONLY if it is transaction-stateful and has taken responsibility for processing or re-sending the request toward its destination. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
