Hi,
Consider the scenario as below:
UAC UAS
| INVITE |
|---------------------------------------------------------------------->|
| 180 |
|<----------------------------------------------------------------------|
| CANCEL 200 OK for INVITE |
|---------------> <-------------------|
Here UAC receives the 200 OK for INVITE after sending CANCEL.
In this case once the UAC receives the 200 OK UAC can continue sessions
established by 2xx or may terminate the call by sending BYE as mentioned in
section 15 of RFC 3261.
Also from RFC 3261 section 9.1 statement, { "Note that both the transaction
corresponding to the original request and the CANCEL transaction will complete
independently."}, the CANCEL and INVITE transactions have to complete
independently.
Now my query is :
Is it valid for UAC to retransmit CANCEL request even after getting 200 OK for
INVITE (until UAC receives 200 OK for CANCEL or CANCEL transaction times out)?
In draft "draft-ietf-sipping-race-examples-01.txt", same scenario is
described in section 3.1.2 but there is no mention of what happens if UAC does
not receive the 200 OK for CANCEL.
{My opinion is that retransmitting the CANCEL after receiving the 200 OK for
INVITE (or even 3xx-6xx) does not serve any purpose as the RFC 3261 itself says
that the UAC can continue sessions established by 2xx or may terminate the call
by sending BYE in such cases. Also at the UAS end, the CANCEL received after
sending the final response is effectively no-op}.
Please provide your valuable inputs.
Thanks,
Praveen Dandin
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