Subject: [AVT] Naming of RTP payload formats within SDP

From: Colin Perkins <[email-masked]>
Date: Tue, 21 Jun 2005 17:25:34 +0100

I'd like to draw the attention of the working group to the IESG draft  
"A question on Media Type Registrations" which has recently been  
submitted:

     http://www.ietf.org/internet-drafts/draft-iesg-media-type-00.txt

There has been considerable controversy on the <[email-masked]>  
mailing list over the use of MIME media types to identify RTP payload  
formats within SDP, triggered by our attempted registration of RTP  
payload formats for real-time text conversation. This has led some in  
the community to review the use of media types to identify RTP  
payload formats, and to suggest it is inappropriate to use the  
existing media types registry for this purpose. The above mentioned  
draft summarises the issues, suggests three possible future  
directions for use of media types, and solicits feedback from the  
community. The three directions are (from section 2 of the draft):

"All media type protocols may specify handling" -- this is  
essentially the status quo, requiring no changes to RTP payload  
format naming in SDP.

"MIME handling is the model for other using protocols" -- this would  
prevent registrations for media types which cannot be passed directly  
to a MIME parser, in effect preventing RTP payload types from using  
the media types namespace and requiring (at least a partial) registry  
split.

"Registry split" -- the media types registry is split into two, with  
all RTP payload formats moving to a new registry. This would require  
updates to all RFCs that define RTP payload formats, reference the  
SDP "m=" and "a=rtpmap:" lines to name RTP payload formats or other  
media types, or reference MIME media types to name RTP payload formats.

I would strongly urge you to read the draft, and to consider the  
effects of either of the latter two directions on RTP, SDP, SIP and  
RTSP. Comments should be sent to either <[email-masked]> or  
<[email-masked]> before 1st July 2005.

Colin

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Audio/Video Transport Working Group
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