Re: [rtcweb] AVPF vs AVP

Hi Roni, 

>As for using AVPF while signaling AVP that will confuse 
>endpoint that so not understand this convention and can 
>support AVPF. They will see an offer with AVP but with 
>parameters that are not part of AVP. They can respond with 
>AVP without the AVPF parameter and behave like AVP endpoints 
>even though they support AVPF. This will prevent them from 
>sending AVPF feedback messages.
>
>This may be a problem for what you call "legacy" video 
>conferencing endpoint. (I do not like the term legacy here 
>since these are not legacy endpoint but AVP/AVPF compliant EPs 

Do those devices support CapNeg?

Regards,

Christer

> > -----Original Message-----
> > From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On 
> > Behalf Of Magnus Westerlund
> > Sent: Wednesday, September 14, 2011 6:09 PM
> > To: rtcweb@ietf.org
> > Subject: [rtcweb] AVPF vs AVP
> > 
> > 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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> > 
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> > 
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