Uttam , You are not supposed to change the answer in the 200 OK .In case you have sent an offer you are not supposed to initiate a new offer until the previous offer/answer exchange is over , In the example you mention , you will need a new offer answer exchange to connect the phone and not change the SDP from the first offer answer .. Refer to the SIP offer answer model for details ... Cheers , Sayan
-----Original Message----- From: Uttam Kumar Sarkar [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 16, 2005 7:36 PM To: 'Christer Holmberg (JO/LMF)'; 'Steven Egan'; Sayan Chowdhury (WT01 - TELECOM SOLUTIONS) Cc: [EMAIL PROTECTED]; [email protected] Subject: RE: [Sip-implementors] SDP in 183 non reliable response Christer, You said "you can assume that the SDP will not change in any additional 18x (or 200) for the same dialog within the same transaction". How about the scenario when announcement is played by media server sent in 183 and then the final response is sent from the phone which would be different. Thanks, Uttam -----Original Message----- From: Christer Holmberg (JO/LMF) [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 16, 2005 7:13 AM To: 'Steven Egan'; [EMAIL PROTECTED] Cc: [EMAIL PROTECTED]; [email protected] Subject: RE: [Sip-implementors] SDP in 183 non reliable response Hi, It is allowed to send an SDP answer an unreliable 18x. The reason it's not considered as a "valid answer" is because it's unreliable, so if it gets lost and a new offer is sent the whole offer/answer state would get out of synch. However, that doesn't mean that you can't use the SDP you receive in un unreliable 18x, und you can assume that the SDP will not change in any additional 18x (or 200) for the same dialog within the same transaction. Regards, Christer Holmberg Ericsson Finland > -----Original Message----- > From: Steven Egan [mailto:[EMAIL PROTECTED] > Sent: 16. helmikuuta 2005 11:35 > To: [EMAIL PROTECTED] > Cc: Christer Holmberg (JO/LMF); [EMAIL PROTECTED]; [EMAIL PROTECTED]; > [email protected] > Subject: Re: [Sip-implementors] SDP in 183 non reliable response > > > Hi Sayan, > I am sending the Invite with no offer to a Cisco AS5350. It is the > AS5350 that is sending back the 183 with SDP (I wouldn't > refer to it as > an offer per se, as it is not a reliable response). I have > no control > over how the 183 response is constructed, so I was looking to > know if it > is allowed to contain the SDP or not. I have not found > anything in the > documentation detailing this. What we are probably going to do is > ignore the 183 SDP and wait for the SDP in the subsequent 200. > Cheers, > Steven > > [EMAIL PROTECTED] wrote: > > Hi, > > Bit confused, but how does this help? > > As I understand the answer for the offer in the 18x (identical SDP > > repeated in the 200), will be answered only in the ACK to > the 200 OK. > > So what's the point in doing an "early offer" in an 18x, as > the offer > > answer can only be completed when the 200 OK/ACK exchange > takes place. > > Does sending an offer in 18x helps in any specific call flow? > > Just curious... > > > > Regards , > > Sayan > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf > Of Christer > > Holmberg (JO/LMF) > > Sent: Wednesday, February 16, 2005 4:11 AM > > To: 'Paul Kyzivat'; Bala Neelakantan > > Cc: [email protected] > > Subject: RE: [Sip-implementors] SDP in 183 non reliable response > > > > > > Hi, > > > > To my understanding the same SDP shall be sent in all subsequent > > provisional responses - no matter if they are sent reliably > or not. You > > can only have at most one offer/answer exchange per SIP > transaction, so > > once you've sent an offer (or answer, if the INVITE did contain an > > offer) in 18x you can't send any more within that transaction. > > > > When it comes to forking, each dialog is handled completely separate > > from each other, ie the offer/answer "state" on one dialog is not > > affected by other dialog. How the UAC then chooses which dialogs to > > accept/reject, and how to handle possible media received > from multiple > > UASs, is an implementation issue. > > > > Regards, > > > > Christer Holmberg > > Ericsson Finland > > > > > >>-----Original Message----- > >>From: [EMAIL PROTECTED] > >>[mailto:[EMAIL PROTECTED] Behalf Of Paul > >>Kyzivat > >>Sent: 15. helmikuuta 2005 18:42 > >>To: Bala Neelakantan > >>Cc: [email protected] > >>Subject: Re: [Sip-implementors] SDP in 183 non reliable response > >> > >> > >> > >> > >>Bala Neelakantan wrote: > >> > >>>Paul, > >>> > >>>I agree that the same SDP should be sent in the subsequent > >> > >>non-reliable > >> > >>>response and also on the first Reliable response. > >> > >>I guess you are shifting from the subject of the original > >>question, and > >>discussing a "normal" invite that includes an offer. > >> > >> > >>>What if the call is forked? In that case, there could be multiple > >>>provisional responses, each could be potentially different? > >> > >> How does the > >> > >>>UAC handle those? > >> > >>This has been well documented and discussed, though it can > >>get complex. > >> > >>The response to each fork creates a separate dialog. It is up > >>to the UAC > >>to keep the different dialogs straight until one is answered and the > >>others are cancelled. > >> > >> Paul > >> > >> > >>>Thanks, > >>>Neel > >>> > >>>-----Original Message----- > >>>From: [EMAIL PROTECTED] > >>>[mailto:[EMAIL PROTECTED] On Behalf > >> > >>Of Paul Kyzivat > >> > >>>Sent: Tuesday, February 15, 2005 9:48 AM > >>>To: Steven Egan > >>>Cc: [email protected] > >>>Subject: Re: [Sip-implementors] SDP in 183 non reliable response > >>> > >>>Well, I went back and read to refresh my memory. I agree > >> > >>that there is > >> > >>>nothing that suggests SDP might be in an unreliable > >> > >>provisional when > >> > >>>there had been no offer in the initial request. > >>> > >>>If it *was* there, you wouldn't be able to consider it a > >> > >>true offer, > >> > >>>since that must be in a reliable request or response. It > >> > >>would have to > >> > >>>be a hint of the offer to come. I don't find any language that > >>>explicitly *prohibits* this. But in the absence of anything > >> > >>suggesting > >> > >>>it might be valid you would be best to not count on it. > >>> > >>> Paul > >>> > >>>Steven Egan wrote: > >>> > >>> > >>>>Hi Paul, > >>>>So you are saying that when an INVITE is sent with no > >> > >>offer, a 183 with > >> > >>>>SDP can be sent in response? > >>>>Can you point me to where exactly this is documented please, as my > >>>>problem is I cannot find anything in RFC 3261 or any other > >> > >>documentation > >> > >>>>to confirm expected behaviour for the 183? > >>>>Cheers, > >>>>Steven > >>>> > >>>>Paul Kyzivat wrote: > >>>> > >>>> > >>>> > >>>>>Steven Egan wrote: > >>>>> > >>>>> > >>>>> > >>>>>>Hi, > >>>>>>Is it valid to include the SDP in a non reliable 183 sent > >> > >>in response > >> > >>>>>>to an Invite with no initial offer? > >>>>>> > >>>>>>It is ok to include the SDP in the 183 when the Invite > >> > >>contains the > >> > >>>>>>initial offer, but RFC 3261 is not clear as to whether > >> > >>the SDP can be > >> > >>>>>>included when no offer is included in the initial invite. > >>>>> > >>>>> > >>>>> > >>>>>I believe the answer is YES. The *same* SDP should be sent in the > >>>>>first reliable response. > >>>>> > >>>>> Paul > >>>> > >>>> > >>>_______________________________________________ > >>>Sip-implementors mailing list > >>>[email protected] > >>>http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > >>> > >> > >>_______________________________________________ > >>Sip-implementors mailing list > >>[email protected] > >>http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > >> > > > > _______________________________________________ > > Sip-implementors mailing list > > [email protected] > > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > > > > > > > > Confidentiality Notice > > > > The information contained in this electronic message and > any attachments to this message are intended > > for the exclusive use of the addressee(s) and may contain > confidential or privileged information. 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