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

From: [email-masked]
Date: Sat, 14 Jun 2008 14:15:02 -0700 (PDT)

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Multiparty Multimedia Session Control Working Group of the IETF.

	Title           : The SDP (Session Description Protocol) Grouping Framework
	Author(s)       : G. Camarillo
	Filename        : draft-ietf-mmusic-rfc3388bis-00.txt
	Pages           : 20
	Date            : 2008-06-12

This document defines two Session Description Protocol (SDP)
attributes: "group" and "mid".  They allow to group together several
"m" lines for two different purposes: for lip synchronization and for
receiving media from a single flow (several media streams) that are
encoded in different formats during a particular session, on
different ports and host interfaces.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-mmusic-rfc3388bis-00.txt

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.
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---

From: "Ali Begen (abegen)" <[email-masked]>
Date: Sat, 14 Jun 2008 15:24:04 -0700

Hi Gonzalo,

One of the (probably the most important) motivations for updating 3388
was to remove the requirement that an "m" line identified by its "mid"
attribute MUST NOT appear in more than one "a=group" line using the same
semantics. 

However, the document below (in Section 5) still has this limitation.
Removing this limitation is essential for FEC Framework and in the last
meeting, the WG agreed to remove this limitation. 

BR,
-acbegen

> -----Original Message-----
> From: [email-masked] 
> [mailto:[email-masked]] On Behalf Of [email-masked]
> Sent: Saturday, June 14, 2008 2:15 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: [MMUSIC] I-D Action:draft-ietf-mmusic-rfc3388bis-00.txt
> 
> This draft is a work item of the Multiparty Multimedia 
> Session Control Working Group of the IETF.
> 
> 
> attributes: "group" and "mid".  They allow to group together 
> several "m" lines for two different purposes: for lip 
> synchronization and for receiving media from a single flow 
> (several media streams) that are encoded in different formats 
> during a particular session, on different ports and host interfaces.
> 
> Below is the data which will enable a MIME compliant mail 
> reader implementation to automatically retrieve the ASCII 
> version of the Internet-Draft.
>

---

From: Gonzalo Camarillo <[email-masked]>
Date: Thu, 26 Jun 2008 10:30:41 +0300

Hi,

as you have probably noticed, the draft contains the same text as 
RFC3388. That is, the first changes will be introduced in version 01. 
The idea with submitting 00 is to kick off the work and to gather 
further requirements from folks on this work.

Therefore, if somebody has additional requirements related to this 
draft, please speak up now.

Cheers,

Gonzalo

---

From: "Ali Begen (abegen)" <[email-masked]>
Date: Thu, 26 Jun 2008 11:07:47 -0700

Hi Gonzalo,

OK, sure. Our most important requirement is to remove the limitation
below.

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.

BR,
-acbegen

> From: Gonzalo Camarillo [mailto:[email-masked]] 
> Sent: Thursday, June 26, 2008 12:31 AM
> To: Ali Begen (abegen)
> Cc: [email-masked]
> Subject: Re: [MMUSIC] I-D Action:draft-ietf-mmusic-rfc3388bis-00.txt
> 
> Hi,
> 
> as you have probably noticed, the draft contains the same 
> text as RFC3388. That is, the first changes will be 
> introduced in version 01. 
> The idea with submitting 00 is to kick off the work and to 
> gather further requirements from folks on this work.
> 
> Therefore, if somebody has additional requirements related to 
> this draft, please speak up now.
> 
> Cheers,
> 
> Gonzalo
> 
> > attribute MUST NOT appear in more than one "a=group" line using the 
> > same semantics.
> > 
> > Removing this limitation is essential for FEC Framework and in the 
> > last meeting, the WG agreed to remove this limitation.
> > 
> > BR,
> > -acbegen
> >