Subject: Re: [MMUSIC] I-D Action:draft-ietf-mmusic-rfc3388bis-00.txt

From: Gonzalo Camarillo <[email-masked]>
Date: Mon, 07 Jul 2008 09:59:16 +0300

Hi,

thanks for your comments. Answers inline:

Ali Begen (abegen) wrote:
> Hi Gonzalo,
> 
> OK, sure. Our most important requirement is to remove the limitation
> below.

I have removed it from the revision I have just submitted:

http://www.ietf.org/internet-drafts/draft-ietf-mmusic-rfc3388bis-01.txt

> Additionally, we recently faced an issue and it might make sense to
> introduce some changes in the revision for this. 
> 
> Currently, section 7.5.3 says "If two m lines are grouped using FID they
> MUST differ in their transport addresses (i.e., IP address plus port)."
> While I believe we should have this requirement, sometimes it is
> possible to have multiple m lines in an SDP that use the same transport
> address, but only one of those streams is active at a time (others being
> inactive).
> 
> Usually, an active stream wouldn't need to be grouped with inactive
> stream(s). However, RFC 4566 says "The semantics of multiple "m=" lines
> using the same transport address are undefined." And in practice, some
> non-100%-compliant SDP parsers may reject the whole SDP simply if they
> observe multiple m lines sharing the same transport address, without
> checking whether these m lines were grouped or not.
> 
> Maybe, we could introduce an escape clause for inactive streams (against
> being checked whether they use a transport address that is also used by
> another m line). I am not sure whether anybody else has a comment on
> this, but if there is a need, we might fix it in this revision.

Note that that restriction only applies to the FID semantics. This is 
because grouping media streams in the way using the FID semantics is 
equivalent to listing a number of codecs in a single m line. Therefore, 
the restriction is a syntactic restriction. If does not limit the 
functionality provided by SDP in any way. If you want to do that, you 
simply need to use a single m line, as usual.

Cheers,

Gonzalo
_______________________________________________
mmusic mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/mmusic