Re: [MMUSIC] Sending a=rtcp-mux-only w/o a=rtcp-mux

On Tue, Feb 7, 2017 at 12:38 PM, Roman Shpount <roman@telurix.com> wrote:

> I want to be able to send rtcp-mux-only. I see plenty of scenarios where
> my solution communicates exclusively with Web browsers. Once they implement
> rtcp-mux-only, given the rate with which browsers are updated, I would
> like, at some point, stop using rtcp-mux instead of inserting legacy flag
> indefinitely.
>

What resource are you conserving here? It's not exactly consuming a lot of
space in the SDP.

-Ekr

Regards,
> _____________
> Roman Shpount
>
> On Tue, Feb 7, 2017 at 3:33 PM, Eric Rescorla <ekr@rtfm.com> wrote:
>
>>
>>
>> On Tue, Feb 7, 2017 at 9:40 AM, Christer Holmberg <
>> christer.holmberg@ericsson.com> wrote:
>>
>>> Hi,
>>>
>>> >> We had a long discussion about this, with many different opinions,
>>> and it would take some time to
>>> >> go through the archive and check everything. But, one opinion was
>>> that it IS useful to send the
>>> >> attribute, as it indicates support of the mechanism.
>>> >
>>> > What does the other side do with that?
>>>
>>> Well, it knows that it doesn't have to include a=rtcp-mux the next time
>>> it wants to do mux-only.
>>>
>>> Obviously, as you suggested in your original e-mail, if we wouldn't
>>> allow a=rtcp-mux-only without a=rtcp-mux (alt #4) in an offer to begin
>>> with, it doesn't matter.
>>>
>>
>> Yeah, I don't think this is a plausible option.
>>
>> At this point it would be great to hear from anyone who thinks that we
>> should allow
>> a=rtcp-mux-only without a=rtcp-mux....
>>
>> -Ekr
>>
>>
>>>
>>> > Is there any precedent for this in SDP?
>>>
>>> Not anything I can think of.
>>>
>>> Regards,
>>>
>>> Christer
>>>
>>>
>>> From: Eric Rescorla <ekr@rtfm.com>
>>> Date: Monday 6 February 2017 at 16:32
>>> To: Christer Holmberg <christer.holmberg@ericsson.com>
>>> Cc: "mmusic@ietf.org" <mmusic@ietf.org>
>>> Subject: Re: [MMUSIC] Sending a=rtcp-mux-only w/o a=rtcp-mux
>>>
>>>
>>>
>>> On Mon, Feb 6, 2017 at 5:57 AM, Christer Holmberg <
>>> christer.holmberg@ericsson.com> wrote:
>>> Hi,
>>>
>>> >>> Following up to myself, I don't think it's sensible for answers to
>>> >>>contain a=rtcp-mux-only, because either you accepted mux, in which
>>> case
>>> >>>all is good, or you rejected it, in which case it was rejected.
>>> >>
>>> >> While I agree that a=rtcp-mux would be enough in the Answer as far as
>>> >>indicating mux is concerned, including a=rtcp-mux-only in the Answer
>>> >>does indicate that the Answerer supports the mux-exclusive mechanism.
>>> >
>>> > I don't see how that's really that useful
>>>
>>> But what harm does it cause?
>>>
>>> I don't think that's the standard here. We should only send indicators
>>> in SDP when they
>>> do something useful.
>>>
>>> -Ekr
>>>
>>>
>>> Regards,
>>>
>>> Christer
>>>
>>>
>>>
>>>
>>> On Fri, Feb 3, 2017 at 9:38 AM, Eric Rescorla
>>> <ekr@rtfm.com> wrote:
>>>
>>> I have been reading the mux-exclusive document and I'm not sure it says
>>> quite what we want. Specifically, S 4.2 says:
>>>
>>>    When an offerer sends the initial offer, if the offerer wants to
>>>    indicate exclusive RTP/RTCP multiplexing for RTP-based media, the
>>>    offerer MUST associate an SDP 'rtcp-mux-only' attribute with the
>>>    associated SDP media description ("m=" line).
>>>
>>>    In addition, if the offerer associates an SDP 'rtcp-mux-only'
>>>    attribute with an SDP media description ("m=" line), the offerer MAY
>>>    also associate an SDP 'rtcp-mux' attribute with the same SDP media
>>>    description ("m=" line), following the procedures in [RFC5761].
>>>
>>> As I understand this text, the offerer may say the following things:
>>>
>>>  1. No a=rtcp-mux: No muxing.
>>>  2. a=rtcp-mux: I am offering RTCP mux
>>>  3. a=rtcp-mux-only + a=rtcp-mux: I will only do RTCP mux
>>>  4. a=rtcp-mux-only: I will only do RTCP mux (same as #3).
>>>
>>> I don't think the last of these is sensible. No current implementation
>>> will know what to do with a=rtcp-mux-only w/o a=rtcp-mux, so this will
>>> result in interop failures. Thus the MAY in the second graf needs to be
>>> a MUST.
>>>
>>> -Ekr
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
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