My opinion is that it is incorrect to send a 400 in this case. But I will appreciate to have a confirmation from the SIP experts in this mailing-list.
Christina Zhao wrote:
I met a problem when I study the SIP Spec. Can anyone give me his/her
advice for that? Thanks a lot.
The scenario is:
1. UA Y invited UA X.
2. UA X 200ed UA Y.
3. UA Y acked UA X. (SIP Session is established)
4. UA X re-invited UA Y. 5. UA Y 200ed UA X. 6. UA X acked UA Y. (It seems that UA Y doesn't get it because UA X receives retransmission of 200 in step 9)
7. UA X re-invited UA Y AGAIN (Is it valid?) 8. UA Y 400ed UA X. (Is it valid?)
9. UA X received retransmission of step 5.
Q1: For UA X, we think step 7 is valid because the first re-invite transaction is already over, is that true? Q2: We are not very clear about step 8. For UA Y, the 2nd re-invite comes before it receives ack of 1st re-invite. What should UA Y do?
Regards
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