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

[Paul Kyzivat <pkyzivat at cisco.com>]

Christer Holmberg wrote:
> 
> 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?

There are no perfect choices here.

What is wrong with just returning any appropriate error response - e.g. 
488? The main problem with that is whether it did/didn't ack the 
response. After considering alternatives, ISTM that this should then 
also mean that the reliable response has not yet been acknowledged, and 
so another PRACK must be sent - preferably one without an offer.

	Thanks,
	Paul

> 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
> 
> 
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Sipping mailing list  https://www.ietf.org/mailman/listinfo/sipping
> This list is for NEW development of the application of SIP
> Use sip-implementors at cs.columbia.edu for questions on current sip
> Use sip at ietf.org for new developments of core SIP
_______________________________________________
Sipping mailing list  https://www.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use sip-implementors at cs.columbia.edu for questions on current sip
Use sip at ietf.org for new developments of core SIP