Re: [xrblock] WGLC on draft-ietf-xrblock-rtcp-xr-synchronization-02.txt

Colin Perkins <csp@csperkins.org> Mon, 04 March 2013 12:15 UTC

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From: Colin Perkins <csp@csperkins.org>
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Subject: Re: [xrblock] WGLC on draft-ietf-xrblock-rtcp-xr-synchronization-02.txt
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On 19 Feb 2013, at 22:44, Shida Schubert wrote:
> This is an announcement of a 2 weeks XRBLOCK WG last call on 
> "Report Block for Synchronization Delay and Offset Metrics Reporting" 
> priorto requesting publication of the document as a proposed standard. 
> 
> Please send your comments, including nits, to the list by the
> 
> 8th of March (Just before the next IETF meeting in Orlando)
> 
> If you read the draft and you see no issues, concerns, or nits, please
> express the fact that you have no issue progressing the draft on the
> list as well. 
> 
> The latest version can be found here:
> 
> http://www.ietf.org/id/draft-ietf-xrblock-rtcp-xr-synchronization-02.txt


Re-reading this, the definition of the RTP Flow Synchronisation Offset Metric Block is perhaps a little confusing. Is the aim to report the synchronisation offset between flows in a single RTP session, or between flows in multiple RTP sessions? The former case seems well supported, but the latter look problematic, since the SSRC space is not unique across sessions (a single CNAME might be sending several flows with the same SSRC, each in a different RTP session, making the "SSRC of reference" field ambiguous). 



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