Re: [AVTCORE] Mandatory nature of RTCP

"Schwarz, Albrecht (Albrecht)" <albrecht.schwarz@alcatel-lucent.com> Mon, 09 May 2011 12:40 UTC

From: "Schwarz, Albrecht (Albrecht)" <albrecht.schwarz@alcatel-lucent.com>
To: Magnus Westerlund <magnus.westerlund@ericsson.com>
Date: Mon, 09 May 2011 14:40:02 +0200
Thread-Topic: [AVTCORE] Mandatory nature of RTCP
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Cc: "Paul Kyzivat (pkyzivat)" <pkyzivat@cisco.com>, "avt@ietf.org" <avt@ietf.org>
Subject: Re: [AVTCORE] Mandatory nature of RTCP
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Fully agree to that view, Magnus!

We may also consider the scenarios of "unidirectional RTP sessions", e.g., just an RTP media flow from RTP endsystem A to RTP endsystem B, but not vice versa.
There might be then an associated RTCP control flow, - a bidirectional RTCP or again a unidirectional RTCP flow (e.g. just from B to A, but not vice versa).
Etc
 

> -----Original Message-----
> From: Magnus Westerlund [mailto:magnus.westerlund@ericsson.com] 
> Sent: Montag, 9. Mai 2011 14:29
> To: Schwarz, Albrecht (Albrecht)
> Cc: Elwell, John; avt@ietf.org; Paul Kyzivat (pkyzivat)
> Subject: Re: [AVTCORE] Mandatory nature of RTCP
> 
> On 2011-05-09 13:20, Schwarz, Albrecht (Albrecht) wrote:
> > RTCP is NOT MANDATORY according RFC 3550.
> > I fail to see any normative statement, too.
> > I could also imagine RTP use cases which do not need at all RTCP. 
> 
> I think I agree that RTCP is not mandated directly. However, 
> in reality it is required. Only in a few very limited usages 
> can one skip to use RTCP.
> 
> If one uses UDP as underlying transport then RTCP is needed 
> to fulfill the congestion control requirements in RFC 3550 
> and the profiles (RFC3551). Both has a SHOULD requirement and 
> that SHOULD exist to allow cases where you have dedicated resource.
> 
> Then we have all the binding information that RTCP provides, 
> like time synchronization (RTCP SR), which to be synchronized 
> (SDES CNAME). Some single media applications can live without 
> this, but any multi-media do need some of this.
> 
> There is a reason why RTP doesn't contain so much hard 
> requirements. RTP is a toolbox and applications are suppsed 
> to pick the pieces it needs.
> And general RTCP is needed in most cases. So I would 
> recommend any one deciding on RTP/RTCP should start with 
> describing what application requirements they have. Then pick 
> the RTP parts.
> 
> But I will guess that SIPREC is likely to need RTCP. But 
> please do your analysis of what you need.
> 
> Cheers
> 
> Magnus Westerlund
> 
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[AVTCORE] Mandatory nature of RTCP Elwell, John
Re: [AVTCORE] Mandatory nature of RTCP Schwarz, Albrecht (Albrecht)
Re: [AVTCORE] Mandatory nature of RTCP Magnus Westerlund
Re: [AVTCORE] Mandatory nature of RTCP Schwarz, Albrecht (Albrecht)
Re: [AVTCORE] Mandatory nature of RTCP Paul Kyzivat
Re: [AVTCORE] Mandatory nature of RTCP Elwell, John
Re: [AVTCORE] Mandatory nature of RTCP Magnus Westerlund
Re: [AVTCORE] Mandatory nature of RTCP Paul Kyzivat