Re: FW: Issue #27: Allow RTP attributes in non-media m= sections
Paul Kyzivat <[email protected]>
| Newsgroups | gmane.ietf.mmusic |
|---|---|
| Message-ID | <[email protected]> |
On 2/18/17 4:35 AM, Christer Holmberg wrote: > Hi, > > I invite anyone who has a suggestion on text that needs to be modified/added/removed to provide a pull request (or send text to the list) to do so; in draft-bundle, draft-mux-attributes, and/or any other specification... IMO it doesn't make sense to put attributes on one bundled m-line that only apply to some other bundled m-line - current or future. As an alternative, how about picking the first tag in the bundle attribute that identifies an m-line of an appropriate type to carry the attribute? Thanks, Paul > Regards, > > Christer > > -----Original Message----- > From: Paul Kyzivat [mailto:[email protected]] > Sent: 17 February 2017 18:51 > To: Taylor Brandstetter <[email protected]> > Cc: Christer Holmberg <[email protected]>; IETF MMUSIC WG <[email protected]> > Subject: Re: [MMUSIC] FW: Issue #27: Allow RTP attributes in non-media m= sections > > On 2/16/17 9:27 PM, Taylor Brandstetter wrote: >> So, to make this work I think it will be necessary to ammend the >> definitions of the particular attributes to specify this usage. And >> then future new attributes that pertain to RTP would also need to >> address this. >> >> >> sdp-mux-attributes already amends the definitions of these attributes, >> such that a TRANSPORT attribute in m= section "A" can be used for >> media described by m= section "B". So, I don't see why it couldn't go >> a step further, and explicitly allow TRANSPORT and IDENTICAL category >> attributes to appear in m= sections with proto values not normally >> used with those attributes. > > I will reserve judgement until I see specific text. > > Thanks, > Paul > >> On Thu, Feb 16, 2017 at 3:50 PM, Paul Kyzivat <[email protected] >> <mailto:[email protected]>> wrote: >> >> On 2/16/17 12:10 PM, Christer Holmberg wrote: >> >> Hi Paul, >> >> I assume you have an opinion on this :) >> >> The suggestion is to allow RTP-specific parameters (SDP rtcp-mux >> attributes etc) in non-RTP m= lines (e.g., data channel). >> >> >> This is a nasty issue. >> >> The problem with allowing this is: what do these parameters *mean* >> when so attached? And where do I look to find out? >> >> I'm not certain if they are currently permitted or not. AFAIK there >> is no *general* mechanism for specifying with which proto values a >> particular attribute may be used. I haven't studied the definitions >> of the "RTP-related" attributes to see if they make a specific >> statement about this. My guess is that they don't, but that they >> only define the meaning in the context of an RTP session. >> >> If that is so, perhaps the rule that unknown attributes are to be >> ignored should apply to those attributes when used with a non-RTP >> media section. But if that rule were to apply, then we would expect >> that with O/A the rules for how these attributes in an offer affect >> what goes in the answer would not apply. I guess that won't be >> sufficient here. >> >> So, to make this work I think it will be necessary to ammend the >> definitions of the particular attributes to specify this usage. And >> then future new attributes that pertain to RTP would also need to >> address this. >> >> IMO this is a can of worms. So my opinion is that these should *not* >> be used with non-RTP m-lines, with or without bundle. >> >> Note that data channel is a special case. While we have agreed not >> to consider it for now, it is possible, in principle, to run RTP >> over a data channel. If that were defined then these attributes >> would also be needed. But then they would not be used as media-level >> attributes. Instead, they would be dcsa attributes. >> >> Thanks, >> Paul >> >> *From:*mmusic [mailto:[email protected] >> <mailto:[email protected]>] *On Behalf Of *Christer >> Holmberg >> *Sent:* 16 February 2017 19:07 >> *To:* Eric Rescorla <[email protected] <mailto:[email protected]>>; mmusic >> WG <[email protected] <mailto:[email protected]>> >> *Subject:* Re: [MMUSIC] Issue #27: Allow RTP attributes in >> non-media m= >> sections >> >> >> >> Hi, >> >> * * >> >> *>*See: >> >> https://github.com/cdh4u/draft-sdp-bundle/issues/27 >> <https://github.com/cdh4u/draft-sdp-bundle/issues/27> >> >> >> https://github.com/rtcweb-wg/jsep/issues/528 >> <https://github.com/rtcweb-wg/jsep/issues/528> >> >> >> >> >> The basic issue is that it's possible to have a situation >> where you >> >> have both >> >> media and data m= sections but the BUNDLE tag is associated >> with the data >> >> >> m= section and now you need to put the TRANSPORT and >> IDENTICAL >> >> >> attributes somewhere. The JSEP editors discussed this and >> came to the >> >> >> conclusion that it should go with the BUNDLE tag (i.e., in >> the data m= >> >> section) >> >> and that BUNDLE should forbid this, but it requires a change >> to BUNDLE. >> >> >> >> >> Did you mean to say that BUNDLE should NOT forbid this? >> >> >> >> Based on your GitHub discussion, my understanding is that you >> want to >> allow to include RTP-specific parameters (‘rtcp-mux’, ‘rtcp’, >> ‘rtcp-mux-only’ attributes etc) in the data m= section. >> >> >> >> To repeat what I said on GitHub: >> >> >> >> This has been discussed in the past, and the outcome has been to now >> allow RTP-specific parameters in non-RTP m= sections. >> >> >> >> A solution would be to simply change the bundle tag when the RTP m= >> sections are added. >> >> >> >> …OR, we change the mux category for the RTP-specific parameters. >> But, >> that of course means they have to be added to every RTP m= section. >> >> >> >> Regards, >> >> >> >> Christer >> >> >> _______________________________________________ >> mmusic mailing list >> [email protected] <mailto:[email protected]> >> https://www.ietf.org/mailman/listinfo/mmusic >> <https://www.ietf.org/mailman/listinfo/mmusic> >> >> > _______________________________________________ mmusic mailing list [email protected] https://www.ietf.org/mailman/listinfo/mmusic