Re: [rtcweb] draft-ietf-rtcweb-jsep-05 - Recycling m-lines

[Paul Kyzivat <[e-mail]>]

On 11/3/13 11:09 PM, Justin Uberti wrote:
>
> On Fri, Nov 1, 2013 at 2:45 PM, Paul Kyzivat <[e-mail]
> <mailto:[e-mail]>> wrote:
...
>     Later in 5.2.2:
>
>         o  If a m= section exists in the current local description, but has
>            its state set to inactive or recvonly, and a new MediaStreamTrack
>            is added, the previously existing m= section MUST be recycled
>            instead of creating a new m= section.  [OPEN ISSUE: Nail down
>            exactly what this means.  Should the codecs remain the same?
>            (No.)  Should ICE restart?  (No.)  Can the "a=mid" attribute be
>            changed?  (Yes?)]
>
>     This seems to assume that there is no existing MediaStreamTrack for
>     these m-lines.
>
> Yes. The text should state that more clearly.
>
>     If there is, then
>     - the m-line shouldn't be recycled.
>     If there isn't, then
>     - where do its address and port come from?
>     - what is managing the RTCP?
>
>
> The m= section will still have completed ICE negotiation, despite being
> marked as inactive. So the address/port information should already be
> present.

*Why* would you do this if there is no MediaStreamTrack and hence no 
possibility of using the port?

IOW, why not use port zero in these cases?

> I don't follow your question about who is managing RTCP.

It may be a misunderstanding on my part.

My thinking is that the MediaStreamTrack is a surrogate for the resource 
that manages the RTP/RTCP for that track. If so, then no track -> no RTCP.

Of course, with bundling, that resource gets spread across multiple 
MediaStreamTracks.

	Thanks,
	Paul