Subject: RE: [Sipping] Some thoughts on fixing early media: early media option-tag

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Wed, 19 Jul 2006 18:11:39 +0200

Hi, 

>>Yep, The issue is that of backward compatibility -- if you fork to a 
>>destination without knowing whether that destination will play nice 
>>with an early-media response, you're back where you started. So we 
>>need a way for a forking proxy to insert an option-tag into a Require 
>>that forces any UA not understanding play-nice-early-media to reject 
>>the request. The forking proxy (or user thereof) then has to figure 
>>out how to deal with the broken destination.
>
>Accept-Contact: *;extensions="early-media";require;explicit
>
>would avoid the request to be forked to elements that dont play along

Do we really need that? It would require elements that would never play
early media in the first place to implement the option-tag, proxies
would have to be updated, and currently deployed elements would never
receive any calls (again, even if they don't have any intention of
playing early media in the first place).

The proxy could still fork to elements that don't "play along", but
there would of course be no guarantee that possible early media sent by
those element would be accepted. It would of course assume that the UAC
does some kind of media filtering, so that early media sent by elements
not supposed to do it doesn't get mixed up with the "real" early media
(if the UAC assumes that there will be media only from one place, and it
will accept that media to come from whatever, there may of course be a
problem with media mixing).

Regards,

Christer

_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP