Hi list I'm seeing the following behavior from an Aastra 400 PBX.
Flow below is ITSP to PBX INVITE> <100Trying <183 w/SDP PRACK> <200OK (PRACK) <180 w/SDP >PRACK <200OK (PRACK) <200OK (INVITE)w/SDP ACK> BYE> <200OK (BYE) Each time the PBX sends an SDP, the version number is incremented even though nothing is changed. ITSP does not like this and sends the BYE. I'm trying to wrap my head around this and to figure out who's at fault here. According to RFC6337 section 3.2 When both UAs support the 100rel extension, they can update the session in the early dialog once the first offer/answer exchange has been completed. To me that means that the UAS can send many provisional responses each with different SDP, each one updates the early dialog as long as PRACK is used. RFC3262 section 8 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 The above does not state that you can't increment the version number without SDP change. Any tips? /Roger _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
