[MMUSIC] Not fixing a=rtcp and rtcp-mux exclusive

[Roman Shpount <[e-mail]>]

Changing the subject since we are not talking just about BUNDLE any more.

On Thu, Jan 21, 2016 at 1:29 PM, Christer Holmberg <
[e-mail]> wrote:

> I don’t think using a=rtcp for signalling mux-exclusive is new
> functionality. We still use it to signal the RTCP port, which in the case
> of mux-exclusive happens to be same as the RTP port.
>
>
>
I agree rtcp mux exclusive is not entirely new functionality for a=rtcp.
What I am trying to say is that at this point a=rtcp attribute is required
to be generated by ICE but it could be safely ignored when received. It
carries no additional or useful information for anything ICE enabled. It
also not used or carries no useful information when legacy server side NAT
traversal is used. In practice, there is no need to parse a=rtcp or do
anything based on its value. With a=rtcp being used to signal rtcp mux
exclusive, modern end points will need to parse a=rtcp and make decisions
based on its value. This extends the lifetime of the feature which is
essentially under-designed and never operated properly. This is the reason
I was asking for a way to signal mux-exclusive for anything ICE enabled
without relying on a=rtcp. I have no problem with a=rtcp being used to
improve interop with legacy end points, but I do not like seeing new use
scenarios which are centered exclusively around a=rtcp. If we do this, we
run into problem that we need to fix all the exiting a=rtcp problems with
offer/answer, which I do not think is even possible in backwards compatible
manner.

Bottom line -- I would prefer another SDP attribute to signal RTCP mux
exclusive which is negotiated over offer/answer so that both end points can
detect that it is used. This attribute can be used in parallel with a=rtcp,
but I believe a=rtcp will be made totally redundant in this case.

I would also like to update ICE-SDP not include a=rtcp when it carries no
additional information. I believe after switching rtcp mux exclusive to a
different attribute and ICE not being required to insert a=rtcp when it
carries no additional information, a=rtcp will almost never be used in
practical deployments, so the need to fix it disappears.
_____________
Roman Shpount