Subject: [MMUSIC] I-D ACTION:draft-ietf-mmusic-media-loopback-08.txt

From: [email-masked]
Date: Mon, 14 Apr 2008 09:45:01 -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		: An Extension to the Session Description Protocol (SDP) for Media Loopback
	Author(s)	: K. Hedayat
	Filename	: draft-ietf-mmusic-media-loopback-08.txt
	Pages		: 34
	Date		: 2008-4-14
	
The wide deployment of Voice over IP (VoIP), Real-time Text and 
    Video over IP services has introduced new challenges in managing 
    and maintaining voice/real-time Text/video quality, reliability, 
    and overall performance.  In particular, media delivery is an area 
    that needs attention.  One method of meeting these challenges is 
    monitoring the media delivery performance by looping media back to 
    the transmitter.  This is typically referred to as "active 
    monitoring" of services.   Media loopback is especially popular in 
    ensuring the quality of transport to the edge of a given VoIP, 
    Real-time Text or Video over IP service.  Today in networks that 
    deliver real-time media, short of running 'ping' and 'traceroute' 
    to the edge, service providers are left without the necessary tools 
    to actively monitor, manage, and diagnose quality issues with their 
    service.  The extension defined herein adds new SDP media 
    attributes which enables establishment of media sessions where the 
    media is looped back to the transmitter. Such media sessions will 
    serve as monitoring and troubleshooting tools by providing the 
    means for measurement of more advanced VoIP, Real-time Text and 
    Video Over IP performance metrics.

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From: Colin Perkins <[email-masked]>
Date: Mon, 21 Apr 2008 14:31:50 +0100

> 	Filename	: draft-ietf-mmusic-media-loopback-08.txt

Reviewing the IANA considerations, I note that this is using an old  
version of the template, slightly different from that in RFC 4288,  
and doesn't follow the usual conventions for registering media types  
for RTP payload formats. It would be helpful if the draft can be  
updated to match the usual template.

The draft states: "Note that RFC 4855 [RFC4855] mandates that RTP  
payload formats without a defined rate must define a rate parameter  
as part of their MIME registration.  The payload format for  
Encapsulated RTP does not specify a rate parameter. However, the rate  
for encapsulated stream is equal to the rate of the stream being  
mirrored". I don't think this is sufficient: the rate needs to be  
specified as a media type parameter, to match the usual rules for  
encoding media type parameters into SDP.

Encoding considerations should note that the data is framed and binary.

 From RFC 4855: "Restrictions on usage: The fact that the media type  
is defined for transfer via RTP MUST be noted, in particular, if the  
transfer depends on RTP framing and hence the media type is only  
defined for transfer via RTP."

Finally, have these RTP payload types been reviewed by the AVT  
working group?

-- 
Colin Perkins
http://csperkins.org/