Hi, Thanks all for the response to my query. And sorry for delaying this email. The draft that Neb had mentioned in the email had the answers to my query (The example in section 3.1.1).
I suppose the following two are acceptable UAS behavior in this case: 1. If the offer answer is completed for an INVITE transaction, i.e. when answer to the offer is send in reliable response (180 Ringing with 100rel option), then the 200 OK for INVITE should not echo the answer SDP. 2. However if the 200 OK for INVITE has SDP it MUST be the last answer SDP (no offer can be initiated). This way there shall be no impact to the media session if the UAC honors the SDP in the 200 OK for INVITE or even if it ignores it. Thanks & Regards, Subbu On Wed, Jan 21, 2009 at 2:29 AM, Nebojsa Miljanovic <[email protected]>wrote: > Subbu, > take a look at the following draft that talks about it. > > > http://www.ietf.org/internet-drafts/draft-ietf-sipping-sip-offeranswer-10.txt > > Section 3.1.1 states that if you are UAS, you should not send any SDP in > 2xx but > if you are UAC, be ready to ignore it. In other words, don't kill a call if > it > is there. > > Unfortunate reality is that many endpoints are hardcoded to expect SDP in > 2xx > even if offer/answer is fully done. And, they end up killing the call if no > SDP > is present in 2xx. > > Neb > > On 1/20/2009 1:30 AM, Subbu Rajendran wrote: > > Hi All, > > Following is example call flow from RFC 3311 (SIP UPDATE Method). Is SDP > a > > must in the 200 OK for INVITE in this case? If it is required, then 200 > OK > > should contain 'answer 3'. Is this a legal behavior as answer in 200 OK > for > > INVITE ('answer 3') is not based on the offer in the INVITE ('offer 1'). > > > > Could anyone please explain or point me to the RFC that explains this > case? > > > > Caller Callee > > > > (1) INVITE with offer 1 > > |---------------------------->| > > > > (2) 180 with answer 1 > > |<----------------------------| > > > > (3) PRACK > > |---------------------------->| > > > > (4) 200 PRACK > > |<----------------------------| > > > > (5) UPDATE with offer 2 > > |---------------------------->| > > > > (6) 200 UPDATE with answer 2 > > |<----------------------------| > > > > (7) UPDATE with offer 3 > > |<----------------------------| > > > > (8) 200 UPDATE with answer 3 > > |---------------------------->| > > > > (9) 200 INVITE (SDP ?) > > |<----------------------------| > > > > (10) ACK > > |---------------------------->| > > > > > > Thanks & Regards, > > Subbu > > _______________________________________________ > > Sip-implementors mailing list > > [email protected] > > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > > > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
