Re: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04

Justin Uberti <juberti@google.com> Mon, 24 April 2017 18:32 UTC

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From: Justin Uberti <juberti@google.com>
Date: Mon, 24 Apr 2017 11:31:38 -0700
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To: Roni Even <roni.even@huawei.com>
Cc: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>, "rtcweb@ietf.org" <rtcweb@ietf.org>
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Subject: Re: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04
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Agree - the differences in protection that you mention are what I was
planning to discuss in the new text.

On Mon, Apr 24, 2017 at 2:59 AM, Roni Even <roni.even@huawei.com>; wrote:

> Hi Sergio,
>
> I understand your distinction between FEC (ulpfec) and  RED with regards
> to the RTP header. Still, the RTP header extensions have their own
> redundancy recommendations so they less less problem for packet loss.
>
> Maybe it will be good in section 3 to add a section that mention that FEC
> will protect the whole RTP packet while RED and in-band fec will only
> protect the RTP payload.
>
>
>
>
>
> Roni
>
>
>
> *From:* Sergio Garcia Murillo [mailto:sergio.garcia.murillo@gmail.com]
> *Sent:* יום ב 24 אפריל 2017 12:09
> *To:* Roni Even; Justin Uberti
> *Cc:* rtcweb@ietf.org
> *Subject:* Re: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04
>
>
>
> AFAIK, FEC (at least ulpfec) protects the full packet, including header
> extensions. When we are addressing the usage of RED vs FEC for audio we
> should note the difference in behavior  and it's possible consequences.
>
> Best regards
> Sergio
>
> On 24/04/2017 11:04, Roni Even wrote:
>
> Hi Sergio,
>
> What I said that the redundancy of RTP header extensions in not a FEC
> issue. FEC addresses the payload and not the RTP header.  RTP header
> extensions are discussed in the RFC5285-bis draft and each new RTP header
> extension must address the issue of loss since RTP over UDP is unreliable.
>
> I am not sure we need any text in rtcweb-fec about RTP header extensions.
> General RTP usage in RTCweb is in the RTCweb RTP usage and this is where
> general redundancy of RTP is discussed, and as a general RTP usage it
> points at redundancy for payload and for RTP header extensions reference
> RFC5285 (rfc5285-bis will obsolete it and have a section about transmission
> consideration.
>
>
>
> In this rtcweb-fec document audio/red is a payload; it is not an RTP
> packet for which you need to address the RTP header redundancy.
>
>
>
> Roni Even
>
>
>
> *From:* Sergio Garcia Murillo [mailto:sergio.garcia.murillo@gmail.com
> <sergio.garcia.murillo@gmail.com>]
> *Sent:* יום ב 24 אפריל 2017 11:28
> *To:* Roni Even; Justin Uberti
> *Cc:* rtcweb@ietf.org
> *Subject:* Re: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04
>
>
>
> Hi Roni,
>
> Not following you. Neither RFC 5265 nor RFC 5265-bis references red/audio,
> also webrtc-rtp-usage references the fec draft when speaking about
> redundancy.
>
> Also, please note that I am not proposing to change current RED behavior
> or its usage within webrtc, just proposing to add a "warning" note to make
> it implicit what is the current situation: When using rtp red for audio,
> only payload is protected, and rtp headers are not, which is almost
> harmless currently but could cause some issues in the future if not taken
> into consideration when using new rtp header extensions.
>
> Best regards
> Sergio
>
> On 24/04/2017 7:43, Roni Even wrote:
>
> Hi Justin,
>
> I am not sure that this is something to discuss here, RTP header
> extensions are discussed in https://tools.ietf.org/html/
> draft-ietf-rtcweb-rtp-usage-26 , which points to RFC5285 soon to be
> replaced  by the rfc5285-bis draft.
>
> The bis draft has a section about transmission considerations see
> https://tools.ietf.org/html/draft-ietf-avtcore-rfc5285-
> bis-09#section-4.1.1 discussing reliability of RTP header extension
> delivery by sending them in multiple RTP packets.
>
>
>
> If you still want to say something you can probably add to section 1 “ Web
> Real-Time Communication (WebRTC) Media Transport and Use of RTP are
> discussed in https://tools.ietf.org/html/draft-ietf-rtcweb-rtp-usage-26”
>
>
>
> Roni
>
>
>
>
>
> *From:* Justin Uberti [mailto:juberti@google.com <juberti@google.com>]
> *Sent:* יום א 23 אפריל 2017 21:48
> *To:* Roni Even
> *Cc:* Sergio Garcia Murillo; rtcweb@ietf.org
> *Subject:* Re: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04
>
>
>
>
>
>
>
> On Sat, Apr 22, 2017 at 10:32 PM, Roni Even <roni.even@huawei.com>; wrote:
>
> Hi,
> Inline
> Roni Even
>
> > -----Original Message-----
> > From: rtcweb [mailto:rtcweb-bounces@ietf.org] On Behalf Of Sergio Garcia
> > Murillo
> > Sent: יום ו 21 אפריל 2017 12:30
> > To: rtcweb@ietf.org; Justin Uberti
> > Subject: [rtcweb] Review comments on draft-ietf-rtcweb-fec-04
> >
> > Hi all, Justin,
> >
> > I have been reviewing current FEC draft and I have a couple of comments:
> >
> > 1. Usage of RED and in band FEC and header extensions in Sections 3.2,
> > 3.3 and 4
> >
> > I think it would be worth noting that neither red/audio nor in-band fec
> allows
> > to recover RTP header extensions from previous packets. The impact of
> > loosing the header extensions will be dependent of its meaning as, for
> > example, this would cause minor problems to SFUs as client to mixer audio
> > level info of previous packets will be lost, but could make it unusable
> for
> > PERC (as it is currently defined) as it requires the OHB header
> extension.
>
>
> [Roni Even] This is not a FEC problem but general RTP header extensions
> reliability discussed in RFC5285 and RC5285-bis draft and in the specific
> RTP header extension.
>
>
>
> Roni, what would you suggest we say in this document?
>
>
>
> >
> > 2. Adaptive use of FEC for bandwidth probing (section 8)
> >
> > I think it would be a good addition to recommend FEC usage for bandwidth
> > proving instead of other alternatives like RTX or padding only packets.
> >
> > Best regards
> >
> > Sergio
> >
> > _______________________________________________
> > rtcweb mailing list
> > rtcweb@ietf.org
> > https://www.ietf.org/mailman/listinfo/rtcweb
>
>
>
>
>
>
>