RFC3264 "An Offer/Answer Model with the Session Description Protocol" (par. 8 Modifying the Session), specifies that:
"At any point during the session, either participant MAY issue a new offer to modify characteristics of the session. It is fundamental to the operation of the offer/answer model that the exact same offer/answer procedure defined above is used for modifying parameters of an existing session. The offer MAY be identical to the last SDP provided to the other party (which may have been provided in an offer or an answer), or it MAY be different. We refer to the last SDP provided as the "previous SDP". If the offer is the same, the answer MAY be the same as the previous SDP from the answerer, or it MAY be different. If the offered SDP is different from the previous SDP, some constraints are placed on its construction, discussed below. Nearly all aspects of the session can be modified. New streams can be added, existing streams can be deleted, and parameters of existing streams can change. When issuing an offer that modifies the session, the "o=" line of the new SDP MUST be identical to that in the previous SDP, except that the version in the origin field MUST increment by one from the previous SDP. If the version in the origin line does not increment, the SDP MUST be identical to the SDP with that version number. The answerer MUST be prepared to receive an offer that contains SDP with a version that has not changed; this is effectively a no-op. However, the answerer MUST generate a valid answer (which MAY be the same as the previous SDP from the answerer, or MAY be different), according to the procedures defined in Section 6." On 26/07/07, Alexeitsev, D <[EMAIL PROTECTED]> wrote: > > > Hello All > > > > Does the value of the session version field in an answer effectively > > mean anything, or does it only have a meaning in an offer? > > > > The problem is that some UAS increment the version number in the > > answer and some UACs interpret it as a new offer and try to answer it > > in the ACK. That leads to all kind of mess. > > > > So who is wrong here - UAS incrementing the version number in the > > answer, or UAC interpreting it as a new offer? > > > > Greetings, > > Denis Alexeitsev > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
