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

[Aniella Juverdeanu]

But it looks like the ACK is after the re-Invite (I don't see the arrow in the diagram but it seems so)

I had similar case in the network where I pushed the vendor of the called party (Bob) to not send the re-Invite before sending the ACK (in my case the vendor for Alice was dropping the call with clear reason that is 200 OK was not ACKed yet). The vendor for Bob argued that RFC 3261 allows this behaviour. Anyway I could not conclude in the end because I had to pursue the vendor for Alice to change the call flow (it was quite complicated due to HOLD and transfer back and forth) that eliminated this behaviour.

So it is still not clear for me if re-Invite before ACK-ing is correct upon RFC. Makes sense to not be correct but so many things make sense and they are not correct:)

Aniella

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of tester voip
Sent: January 8, 2014 01:55 AM
To: AOEKING
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] reINVITE sent by callee before receiving ACK

nuwan,

you are corect in saying that the re-invite should get rejected if it is received before dialog establishment.
but for the cale the dialog is already established as it has sent the ack.so it shouldnt reject the reinvite.

On Sat, Jan 4, 2014 at 10:45 PM, AOEKING <aoeking at gmail.com<mailto:aoeking at gmail.com>> wrote:
If the re-INVITE received before the dialog establishment that re-INVITE will be rejected.

Use SIP UPDATE mechanism to avoid this kind of race conditions

Cheers
Nuwan

On Thu, Dec 19, 2013 at 11:18 PM, tester voip <tester.voip1 at gmail.com<mailto:tester.voip1 at gmail.com>> wrote:
hi,
as per the rule re-invite is sent by either party when the dialog is estabnlished.
here the caled party sends before receiving ack i.e dialog not established.

although alice wont reject it as it has sent the ack already.
alice sends 200ok for it.

please corect me if m wrong.

On Tue, Dec 17, 2013 at 7:58 PM, Talha Koc <talha.koc at huawei.com<mailto:talha.koc at huawei.com>> wrote:
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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