Dear Christer Holmberg
Very nice question. Or say that it is important. It is about the fine semantics of suspending/resuming of session modification.
Considering the session modification with more than one preconditions. And there are more than one Offer/Answer pairs used as preconidtion notification(such as more than one UPDATE/200OK before final response of Re-INVITE).
The session modification would be suspended until all the precondition is OK. And at that time, the session modifcation resumed(just resumed, mot committed. Commitment may by other thing, such as "late commitment of 200OK of Re-INVITE".). And at that time, the effect of all Offer/Answer pairs with precondition can be same as one Offer/Answer pair without precondition.
So, the rollback of session state with precondition would not according as precondition state.
And the two sides can have different precondition. Even if one side's preconditon OK and the other side is not, both sides would rollback.
Gaoyang
| "Christer Holmberg"
<christer.holmberg@xxxxxxxxxxxx>
2009-02-19 03:24 |
|
Hi,
Let's look into this precondition proposal.
There are some issues that needs to be taken into consideration.
Issue 2:
-----------
Assume I send a re-INVITE, and I use precondition. I modify the SDP, and indicate that preconditions are not met.
Then I receive a relaible 18x, and the first offer/answer transaction has succeeded.
Later I send an UPDATE request, where I indicate that preconditions are met.
Then I receive a 200 for the UPDATE, indicating that preconditions are met also at the other end.
Then the re-INVITE fails. Now, according to the ZTE proposal, is there a full fallback? The UPDATE was sent as part of the nested precondition procedure, but the preconditions were fullfilled before the re-INVITE failed?
Does it matter what the precondition state is when the re-INVITE fails, or is there always a full fallback?
Regards,
Christer
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