Subject: [AVT] RTP: SSRC multiplexing for same medium

From: Stephen Casner <[email-masked]>
Date: Tue, 7 Jan 2003 15:17:37 -0800 (PST)

At Yokohama, we discussed multiplexing streams distinguished by
different SSRC identifiers within one RTP session.  This discussion
was in the context of the retransmission draft.  One or more people
requested that a sentence be added to Section 5.2 in the RTP spec to
say that SSRC multiplexing was OK for streams of the same medium
(vs. different media which is the primary emphasis of that section).
Here is the sentence I added.  Is it a good idea or bad idea to add
this?  If you think adding such a statement is a good idea, does this
sentence say the right thing?

                                                        -- Steve

OLD:
   Using a different SSRC for each medium but sending them in the same
   RTP session would avoid the first three problems but not the last
   two.
NEW ADDITION:
   It may be appropriate to multiplex streams of the same medium
   using different SSRC values in one RTP session in scenarios where the
   last two problems do not apply.

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 07 Jan 2003 23:20:01 -0500

I generally support the idea of multiplexing using SSRC. However, I 
found the text a bit inadequate for a couple of reasons:

1. multiplexing using different SSRC for the same media on the same RTP 
session is going to be the default case for multicast sessions, no? The 
text makes it sound like such a thing is an exception. Its true for 
unicast, but this section seems multicast-centric anyway.

2. Does this text imply that an RTP receiver MUST be prepared to receive 
multiple multiplexed streams on a single session? I expect most 
implementations today using unicast are not prepared for that (although 
I believe they should be)

My apologies if these were already discussed during Yokohama; I believe 
I missed that session.

-Jonathan R.

-- 
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