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

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.

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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