Re: [MMUSIC] Bundle and "m=" line terminology [Re: Review of draft-ietf-mmusic-sdp-bundle-negotiation-32 (Part I)]

[Christer Holmberg <[e-mail]>]

Hi,

As Ekr said, the issue is not “m= line” versus “media description”. It’s more whether e.g., an SDP attribute belongs to a media description, is within a media description, or is associated with a media description/m- line.

The reason I use “associated” is because I have many times been told that an attribute is not part of a media description/m- line (compared to e.g., the port and proto value).

Regards,

Christer

From: Eric Rescorla <[e-mail]<mailto:[e-mail]>>
Date: Sunday 6 November 2016 at 21:01
To: Flemming Andreasen <[e-mail]<mailto:[e-mail]>>
Cc: Christer Holmberg <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: Bundle and "m=" line terminology [Re: [MMUSIC] Review of draft-ietf-mmusic-sdp-bundle-negotiation-32 (Part I)]



On Thu, Nov 3, 2016 at 8:31 PM, Flemming Andreasen <[e-mail]<mailto:[e-mail]>> wrote:

Christer reminded me to pick up the part below:


On 10/3/16 10:00 AM, Eric Rescorla wrote:


On Mon, Oct 3, 2016 at 4:01 AM, Christer Holmberg <[e-mail]<mailto:[e-mail]>> wrote:

<snip>
>S 10.3.1.1.
>   When an offerer generates an initial offer, the offerer MUST
>   associate either an SDP 'rtcp-mux' attribute [RFC5761] or an SDP
>   'rtcp-mux-only' attribute [I-D.ietf-mmusic-mux-exclusive] with each
>   bundled RTP-based "m=" line in the offer.  The offerer MUST associate
>   an SDP 'rtcp-mux-only' attribute with each bundle-only "m=" line.  If
>   the offerer associates a 'rtcp-mux-only' attribute with an "m=" line,
>   the offerer may also associate a 'rtcp-mux' attribute with the same
>   "m=" line, as described in [I-D.ietf-mmusic-mux-exclusive].
>
> This is a particularly egregious case of associate disease that could
> be easily solved by using "add" when referring to the attributes
> you put in the m= section.

People have previously said that you don’t “add” attributes to m- lines: you add port values etc, but not attributes.

This is an example of where I’ve had to re-write big parts of the documents a number of times already, because every time someone else reads the document he/she is not happy with the terminology. I just don’t want to do it again.

The terminology that JSEP uses is that "m= sections" include attribute lines.

I think this is a lot clearer.

 I don’t personally disagree, but there are people that have had other opinions.

 In general I think it would be really useful to have common terminology in BUNDLE and JSEP, but I don’t want to re-write the document once again, and then later be told to do it again…

Resolving the appropriate terminology seems like a chair issue.

RFC 4566 (SDP) Section 5 makes it pretty clear that a Media Description consists of an "m=" line optionally followed by a number of other lines (typically attribute lines). In other words, an "m=" line and a media description is generally not synonymous.

Earlier versions of bundle did not reflect that distinction properly, and about a year ago, I asked for the terminology to be aligned with RFC 4566. There were a few off-list comments from other people that agreed with that view and the draft got updated accordingly (as of -24). That is what the current bundle draft does and I continue to believe that is what it should do.

This message leaves me extremely puzzled because I'm not saying otherwise, and that's why JSEP uses "m= section" for this concept. Media description would also be fine. What is problematic is the use of "associated with an m= line" to mean "part of a media description" or "part of an m= section". That text is extremely confusing, especially when the word "associated" is used in a number of other concepts. So, what I'm asking for is one of the alternative terms I list here.

-Ekr


Thanks

-- Flemming (with chair hat on)



-Ekr


Regards,

Christer






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