Hi Peter, RFC 3262 for UAS section 3 clearly says "After the first reliable provisional response for a request has been acknowledged, the UAS MAY send additional reliable provisional responses. The UAS MUST NOT send a second reliable provisional response until the first is acknowledged. After the first, it is RECOMMENDED that the UAS not send an additional reliable provisional response until the previous is acknowledged. The first reliable provisional response receives special treatment because it conveys the initial sequence number. If additional reliable provisional responses were sent before the first was acknowledged, the UAS could not be certain these were received in order."
For UAC behavior section 4 says " Handling of subsequent reliable provisional responses for the same initial request follows the same rules as above, with the following difference: reliable provisional responses are guaranteed to be in order. As a result, if the UAC receives another reliable provisional response to the same request, and its RSeq value is not one higher than the value of the sequence number, that response MUST NOT be acknowledged with a PRACK, and MUST NOT be processed further by the UAC. An implementation MAY discard the response, or MAY cache the response in the hopes of receiving the missing responses.The UAC MAY acknowledge reliable provisional responses received after the final response or MAY discard them." But for sure it increases the traffic. On Wed, Jul 21, 2010 at 1:20 PM, Peter Nijhuis < [email protected]> wrote: > Hello All, > > I'm facing the following problem: > > An incoming call is first ringing on a call center queue: > The UAS is sending a 180 Ringing with SDP and a require: 100rel, the UAC > responds with a PRACK and the UAS again with an 200 OK. > > Then the call is actually ringing on a UA (IP hardphone) > The UAS send a 180 Ringing again with an SDP and a require:100rel, but > the UAC ignores this as is seems a duplicate message. > > > <-- > INVITE/SDP supported: 100rel > > 100 Trying --> > > 180 Ringing/SDP --> > Require: 100rel RSeq:1 > <-- PRACK > > > 200 OK --> > > 180 Ringing/SDP --> > Require: 100rel RSeq:2 > > 180 Ringing/SDP --> > Require: 100rel RSeq:2 > > 180 Ringing/SDP --> > Require: 100rel RSeq:2 > > 180 Ringing/SDP --> > Require: 100rel RSeq:2 > > 180 Ringing/SDP --> > Require: 100rel RSeq:2 > > > Is the UAS allowed to send multiple 180 Ringing with a require header > field? > > Best Regards, > > Peter Nijhuis > > > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > -- cheers!!!! sarvpriya _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
