Re: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

To: "Christer Holmberg" <christer.holmberg at ericsson.com>, "sipping LIST" <sipping at ietf.org>

Subject: Re: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

From: "Sanjay Sinha (sanjsinh)" <sanjsinh at cisco.com>

Date: Wed, 27 Aug 2008 13:26:14 -0400

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Thread-topic: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

Title: Remaining offer/answer issue: how to reject an SDP offer sent in PRACK

Yeah, probably it was a dumb question.

I am ok with the option of rejecting the offer with 4xx response, indicating that Prack is complete, but offer is not acceptable.

Sanjay

From: Christer Holmberg [mailto:christer.holmberg at ericsson.com]
Sent: Wednesday, August 27, 2008 3:52 AM
To: Sanjay Sinha (sanjsinh); sipping LIST
Subject: RE: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

Hi,

What reasons do you normally have for rejecting an offer? You don't like what has been offered, or you are not able to provide was have been offered.

Regards,

Christer

From: Sanjay Sinha (sanjsinh) [mailto:sanjsinh at cisco.com]
Sent: 27. elokuuta 2008 0:54
To: Christer Holmberg; sipping LIST
Subject: RE: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

What is the reason for rejecting the offer, because of negotiation failure or the fact that UAS does not like updated offer in Prack.

From: sipping-bounces at ietf.org [mailto:sipping-bounces at ietf.org] On Behalf Of Christer Holmberg
Sent: Tuesday, August 26, 2008 2:03 AM
To: sipping LIST
Subject: [Sipping] Remaining offer/answer issue: how to reject an SDP offersent in PRACK

Hi,

Now when we agreed on a way on how to solve the re-INVITE fallback issue, one remaining open issue in the offer-answer draft is how to reject SDP offers sent in PRACKs.

I would like to collect ideas on how it could be done.

NOTE: At this point I DO NOT want to discuss the pros/cons of different alternatives, their impacts on existing normative text, or whether they work in the first place, but simply do some brainstorming :)

Some ideas:

-       Reply 200 OK without SDP answer

-       Reply with 4xx responses, indicating that the PRACK itself was ok, but the SDP offer was rejected

-       Reply 200 OK with "dummy" SDP answer, then immediately send UPDATE with fallback SDP offer

-       Do not use PRACK for offer/answer in the first place

-       Stop using 100rel all together (Dean's proposal in the War On Forking)

Some more?

Personally I don't see a make-sure-you-send-an-offer-which-will-not-be-rejected alternative as feasible, because the UAS may want to reject the offer based on other circumstances (e.g. overload).

Regards,

Christer

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