Subject: [Fecframe] Using the same CNAME for multiple hosts

From: "Roni Even" <[email-masked]>
Date: Fri, 6 Mar 2009 18:00:53 +0200

I am resending again to fecframe.

Hi Ali,

I had some offline discussion with Colin and Steve Casner.

All of us think that this approach is OK. RFC 3550 does not require that the
CNAME will be attached to a specific endpoint.

The relevant text is

"

If each application creates its CNAME independently, the resulting

   CNAMEs may not be identical as would be required to provide a binding

   across multiple media tools belonging to one participant in a set of

   related RTP sessions.  If cross-media binding is required, it may be

   necessary for the CNAME of each tool to be externally configured with

   the same value by a coordination tool. "

This says that you will need a way to coordinate the CNAME and to keep it
for the relevant streams.

Example is a video with repair stream and the associated audio stream should
all have the same CNAME.

Note that you may have a case when one host (FEC encoder) may use multiple
CNAMEs.

The PROBLEM I see is with RFC 5109 mostly section 14.1 that explains why you
shall not multiplex both streams based on SSRC.

This was a change from RFC 2733. Maybe it will be good to review this text
in RFC 5109 and update the draft.

Regards

Roni Even