Subject: [AVT] Comments on draft-ietf-avt-rtcpssm-13 part 1

From: Tom Taylor <[email-masked]>
Date: Wed, 04 Jul 2007 20:53:15 -0400

These comments come way too late given the looming I-D deadline, but they may be 
helpful.

1. I suggest putting the Definitions section before the section describing basic 
operation, so the latter can build on the definitions without repeating them.

2. I found some points in the architecture were unclear. In particular, do the 
Media Senders send their RTCP sender reports to the Distribution Source or to 
Feedback Target instances?  The reason I ask this is because I wasn't sure why 
the the Media Senders needed to be configured with the transport addresses of 
the Feedback Target instances.

3. Is the following paragraph a correct summary of basic operation? If so, it 
might be considered as a replacement for much of the "Basic Operation" section.

(Editorial note: capitalization of "Media Sender", Distribution Source", and 
Feedback Target" needs to be made consistent throughout the document.  I show 
the terms captialized, but the alternative is equally acceptable.]

"One or Media Senders send RTP and RTCP sessions to the Distribution Source. 
The Distribution Source relays the RTP sessions to the receivers using a 
source-specific multicast arrangement.  In the reverse direction, each receiver 
transmits a unicast RTCP stream to a specific instance of the Feedback Target. 
Each Feedback Target instance sends either the original RTCP reports (the Simple 
Feedback Model) or summaries of these reports (the Summary Feedback model) to 
the Distribution Source, using unicast transport if it is not actually 
co-located with the Distribution Source.  The Distribution Source in turn relays 
the RTCP reports and/or summaries to the Media Sender(s). The Distribution 
Source also transmits the RTCP sender reports and receiver reports or summaries 
back out to the receivers, using source-specific multicast."

More later.

Tom

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