Re: [AVTCORE] RTP Topology addition (was: Design choice comments..._

"David Benham (dbenham)" <dbenham@cisco.com> Mon, 23 March 2015 18:59 UTC

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From: "David Benham (dbenham)" <dbenham@cisco.com>
To: Magnus Westerlund <magnus.westerlund@ericsson.com>, "stewe@stewe.org" <stewe@stewe.org>
Thread-Topic: RTP Topology addition (was: Design choice comments..._
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Date: Mon, 23 Mar 2015 18:59:49 +0000
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Subject: Re: [AVTCORE] RTP Topology addition (was: Design choice comments..._
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> From: Magnus Westerlund [mailto:magnus.westerlund@ericsson.com]
> >> I think you need to start by actually describing in which way this
> >> RTFS is different from the RTP mixer or the SFM. Is this really
> >> different from what is already described, or simply a variant?
> >
> > From the doc, the SFM appears to require, like the media switching
> > mixer referenced, a collection of its own SSRCs (ie, terminating
> > SSRCs on all legs), sending only a finite set of SSRC values
> > downstream to any given recipient or a 'cascade link' to another box.
> >
> The point of the SFM is that all SSRCs that exist upstream is projected
> into the downstream. The point is that a selected set of the incoming
> streams that are forwarded and rewritten according to need. SSRC
> possibly, sequence number almost always needed, and often PT.
> 
> > Is an SFM allowed per the definition to reuse the senders/upstream
> > SSRCs, sending a potentially unlimited set of SSRCs downstream/to any
> > given recipient?  Is allowing that a variant or?
> 
> Yes, that is possible. A point is that the SFM has a responsibility for
> downstream congestion control.

Great.    Others have asserted the SSRC termination and SN rewrite in the RTP header (sans header extension options) were absolutes.   And from my read, the text mostly to supported that assertion.   

Would it be friendly to the process to do some tweaking to SFM/sect 3.7 wording to make that bottom-line point of yours?   Hence SSRC and SN rewrite in the RTP header are but one way (alebit historically most common), but that not rewriting those values in the RTP header is allowed per the SFM definition.

I don't think I can work on that until late in the week, definitely not before tomorrow's agenda.   Can Stephan or another buddy up with me on such a text tweaking exercise?

> Cheers
> 
> Magnus Westerlund
> 
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