[SIPForum-discussion] reINVITE sent by callee before receiving ACK

[Talha Koc]

Hi all,

I would like to get your opinions about the race condition shown below.
In this scenario, Bob sends a re-INVITE with a new offer before receiving the ACK for the offer 1.

Does this violate the offer/answer model? What is the correct behavior for Alice here in this position?
Should Alice accept the offer and respond with 200OK with offer2, or should Alice reject it based on the following rule?

RFC 6337 2.2:
"There may be ONLY ONE offer/answer negotiation in progress for a
   single dialog at any point in time."


        Alice                             Bob
          |                                |
          |        INVITE w/offer1         |
          |------------------------------->|
          |             180                |
          |<-------------------------------|
          |                                |
          |      200 INVITE w/answer1      |
          |<-------------------------------|
          |                    reINVITE    |
          |   ACK              w/offer2    |
          |-------------     --------------|
          |              \ /               |
          |               X                |
          |              / \               |
          |<------------     ------------->|
          |             ???                |
          |------------------------------->|
          |                                |

Note: I checked RFC 5407 3.1.4 for a similar scenario, but in that case reINVITE is sent by the caller, not callee.
Note2: This is my first post in the mailing list.

Regards,
Talha


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