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

[Eric Rescorla <[e-mail]>]

On Mon, Nov 7, 2016 at 1:52 AM, Christer Holmberg <
[e-mail]> wrote:

> 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).
>

I had understood the difference between m= line and media description to
precisely be that the media description contained the attributes and the m=
line did not.

-Ekr


> Regards,
>
> Christer
>
> From: Eric Rescorla <[e-mail]>
> Date: Sunday 6 November 2016 at 21:01
> To: Flemming Andreasen <[e-mail]>
> Cc: Christer Holmberg <[e-mail]>, "[e-mail]"
> <[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]>
> 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]> 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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>