Subject: Re: [Sip] Mandatory and Optional streams in Session Descriptions

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 18 Dec 2001 13:40:41 -0500

Moving to mmusic, since it relates to offer/answer.

There is no such mechanism defined. Generally the goal is to set up 
communications whenever possible with whatever overlaps.

-Jonathan R.

De Leo Walter wrote:

> Is there any mechanism to mark an m line as mandatory so that if no offered
> codec is supported by the answerer for the mandatory streams the whole
> session is rejected?
> 
> 
> 
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---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 18 Dec 2001 14:47:12 -0500

However, there appears to be a common behavior to refuse calls when no
media can be negotiated. While media-less calls are legal, they don't
seem to be popular. Even this isn't necessarily a good thing. It might
be better to accept a media-less call and let the endpoint that made the
offer decide what to do; perhaps there is a useful reinvite to recover.

Not clear to me to what extent this kind of behavior should be specified
vs left as implementation choice. 

	Paul