update! Thanks Ryan, Paul and Alex,
Yes, I think to use PRACK with a SDP answer which can give a graceful reply for the SDP offer of an 18x reliable provisional response. For this time the call is still in early state and can be take down by CANCEL. For Alex's concern, I think in the same dialog, any attribute, such as media stream, can be changed by a request, such as re-INITIVE/UPDATE, not a response. If we accept a new SDP offer carried by reliable 18x response, it means the UAC has to send a request with a corresponding answer. Perhaps it is not good enough for SDPofer/answer model. At the same time, if a request with a SDP answer to reply the SDP offer in a response it will leads to a transation loop, such as UPDATE with a SDP offer is replied for the 180 Ringing. So I guess we do not encourage a response with a SDP offer. Its implementation is also simple and clear. Thanks, Christina UAC UAS | INVITE w/offer1 | |-------------------->| | 180 Trying | |<--------------------| | 183 (SDP answer) | |<--------------------| | PRACK | |-------------------->| | 200 OK(PRACK) | |<--------------------| | 180 Ringing(offer) | |<--------------------| | PRACK(answer) | |-------------------->| | CANCEL | |-------------------->| | 200 OK(CANCEL) | |<--------------------| | ACK | |-------------------->| On 3/5/08, christina yuen <[EMAIL PROTECTED]> wrote: > > Thanks Ryan, Paul and Alex, > > Yes, I think PRACK with a SDP answer can give a graceful reply for the SDP > offer of an 18x reliable provisional response. For this time the call is > still in early state and can be take down by CANCEL. > > For Alex's concern, I think in the same dialog, any attibute can be > changed by a request, such as re-INITIVE/UPDATE. > If we accept a new SDP offer carried by reliable 18x response, it means the > UAC has to send a request with a corresponding answer. Perhaps it is not > good enought for SDPofer/answer model. > > At the same time, if UPDATE with a SDP offer is replied for the 180 > Ringing there will be a transation loop. And it surely beyond the timer. So > the way that just do not encourage a response with a SDP offer is simple > and clear. > > Thanks, > Christina > > UAC UAS > | INVITE w/offer1 | > |-------------------->| > > | 180 Trying | > > |<--------------------| > | 183 (SDP answer) | > > |<--------------------| > > | PRACK | > |-------------------->| > > | 200 OK(PRACK) | > > |<--------------------| > > | 180 Ringing(offer) | > > |<--------------------| > > | PRACK(answer) | > |-------------------->| > > | CANCEL | > > |-------------------->| > > | 200 OK(CANCEL) | > > |<--------------------| > > | ACK | > > |-------------------->| > > > On 3/5/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > > Thanks paul! > > Now what I am concerned with is: why in this case, the 180 Ringing is > > not permitted to carry SDP? Based on what kind of consideration? Thanks! > > > > > > > > Alex Zhang > > ESN: 6-554-8782 > > > > > > -----Original Message----- > > From: Paul Kyzivat [mailto:[EMAIL PROTECTED] > > Sent: Tuesday, March 04, 2008 11:48 PM > > To: Alex Zhang (GDNTRND) > > Cc: [EMAIL PROTECTED]; [email protected] > > Subject: Re: [Sip-implementors] what about swich behaviors when it > > receivesan180 Ringing with an new SDP offer? > > > > > > > > [EMAIL PROTECTED] wrote: > > > Hi Paul, > > > > > > I think she is querying what the UAC will react to the 180 ring > > > message with a SDP offer. As we know, if the initial invite contains > > > the SDP offer, then the first 18x reliable provisionable response > > > could carry the answer. This 1st 18x could be the 183 session > > > progress, so will the subsequent 180 ring message with the SDP offer > > > be rejected or accpeted by the PRACK message? > > > > So is the following: > > > > UAC UAS > > | INVITE w/offer1 | > > |-------------------->| > > | Rel 183 w/answer1 | > > |<--------------------| > > | PRACK | > > |-------------------->| > > | 200 (PRACK) | > > |<--------------------| > > | Rel 180 w/SDP | > > |<--------------------| > > | ??? | > > |-------------------->| > > > > the case you are concerned with? > > > > In that case the 180 is not permitted to contain SDP, so this is an > > error case. It is however not so clear what to do about it. What you > > want here is a PRNACK, but we don't have that. So you either: > > - withhold the PRACK, which will cause the response to be > > retransmitted until it times out and fails the dialog. > > - send the PRACK, then send CANCEL or BYE to kill the call > > - send the PRACK and cope with the revised SDP in some way. > > (If it is the same as answer1 then it might make sense to > > ignore it. If it is different than answer1 it isn't at all clear > > what to do.) > > > > Because this is an error case I think you can choose to do as you wish. > > > > Paul > > > > > > > > > Alex Zhang > > > ESN: 6-554-8782 > > > > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] > > > [mailto:[EMAIL PROTECTED] On Behalf Of > > > Paul Kyzivat > > > Sent: Monday, March 03, 2008 9:24 PM > > > To: christina yuen > > > Cc: [email protected] > > > Subject: Re: [Sip-implementors] what about swich behaviors when it > > > receivesan 180 Ringing with an new SDP offer? > > > > > > christina, > > > > > > I'm sorry, but I can't figure out what you are asking below. > > > > > > If you haven't already, see if > > > > > > http://www.ietf.org/internet-drafts/draft-ietf-sipping-sip-offeranswer > > > -0 > > > 6.txt > > > > > > answers your question. > > > > > > Paul > > > > > > christina yuen wrote: > > >> My understanding is > > >> > > >> 1> if an SDP offer received in a SIP request, such as all media > > >> 1> streams > > >> in the SDP offer, => the SDP answer is returned in a 488 Not > > >> Acceptable Here response and a SIP607 log is generated. > > >> > > >> 2> If an SDP offer received in a provisional response, such as > > >> 2> all > > > > > >> 2> media > > >> streams in the SDP offer, => it must be rejected, the SDP answer is > > >> returned in the PRACK. > > >> > > >> > > >> > > >> Now an new SDP offer is received in a provisional response, 180 > > >> Ringing, then the switch should reject the SDP offer in PRACK. Do you > > > > >> think it is right? Thanks. > > >> > > >> > > >> > > >> Christina > > >> _______________________________________________ > > >> 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 > > > > > > _______________________________________________ > > > 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
