Re: [rtcweb] AVPF vs AVP

I am shocked, Shocked!, to see you suggest that we disregard RFC 4585 and SDP rules, when we have an IETF specified means of indicating multiple profile support using RFC 5939 SDP Capability Negotiation.
;)

-hadriel

On Sep 14, 2011, at 11:08 AM, Magnus Westerlund wrote:

> Hi,
> 
> There has been this long thread with the subject partially containing
> "AVPF". I want to clarify something in this context around AVPF. Rather
> than the SRTP question.
> 
> An end-point that is AVPF compliant is in fact interoperable with an AVP
> one as long as the trr-int parameter is set reasonably large. A
> parameter value of 1.5-5 seconds (I would recommend 3s) will ensure that
> they are in fact compatible. This avoids the risk of any side timing out
> the other if the AVP side is using the default 5 s minimum interval.
> 
> Based on this one could in fact have the RTCWEB nodes always use AVPF
> for RTP/RTCP Behavior. The AVPF feedback messages are explicitly
> negotiated and will only be used when agreed on.
> 
> This leaves us with any signaling incompatibilities when talking to a
> legacy device. If one don't want to use cap-neg I see two directions to go:
> 
> 1) RTCWEB end-point will always signal AVPF or SAVPF. I signalling
> gateway to legacy will change that by removing the F to AVP or SAVP.
> 
> 2) RTCWEB end-point will always use AVPF but signal it as AVP. It will
> detect the AVPF capabilities of the other end-point based on the
> signaling of the feedback events intended to be used.
> 
> I think 1) is cleaner for the future. 2) might be more pragmatic.
> 
> In both cases I believe there are methods for negotiating a lower
> trr-int than some AVP fallback value to preserve interoperability.
> 
> 
> However, this still don't resolve the question if the "S" should be in
> front of the RTP profile indicator or not. But it might help by removing
> the F or not in the profile.
> 
> Cheers
> 
> Magnus Westerlund
> 
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