Re: [dispatch] Draft on Discarding Priority of RTP Video Packets

[Toerless Eckert <[e-mail]>]

I to had a draft in this area:

https://datatracker.ietf.org/doc/draft-carlberg-avtext-classifier/

We gave up on proceeding with the ideas because back then we where at
the first wave of end-to-end encrypting everything. Especially whatever could
help the network to do a better job. Including RTP extension headers. "Privacy beats
a better network". I am not sure if we have overcome that pendulum swing. I 
would love to hear more support for supporting working on this direction again.

There have been measurements made as to the effectiveness of priority dropping
for media stream packets, and it does provide non-negligible performance
benefits. Unfortunately i am not aware of published work results.

There was, maybe still is network equipment doing DPI into known media headers,
for example MPEG packet types, and it is possible to configure routers
to accordingly match this to differently configured drop priorities (such
as different WRED profiles). So in reality, deployments in broadcast/contribution
networks may have already used some of these technologies without IETF being
aware of it.

There are some good number of advanced topics to consider.

For example, if the network is supporting priority-drops, it does help a lot
to optimize the codec to create more discardable P-frames, and to consider
shaping the ordering of packets in the stream to have packets of such frames
interspersed with packet from a neighboring higher priority frame So that
one can most effectively apply in-network packet dropping without incurring
more queuing latency on network elements than minimally necessary (instead
punting the responsibility of burst management to the sender).

When different streams have different percentages of data of different
priorities, then it will be hard to achieve per-flow stateless discard
behavior without creating unfairness: Flows with average higher priority
will get more throughput.

Cheers
    Toerles

On Wed, Jul 13, 2022 at 10:18:45AM +0300, Ron Even wrote:
> Hi,
> I had a proposal in the past to use
> https://datatracker.ietf.org/doc/html/draft-ietf-avtext-framemarking-13 for
> defining priority in the past. see
> https://datatracker.ietf.org/doc/html/draft-even-avtcore-priority-markings-03
> .
> Roni Even
> 
> On Wed, Jul 13, 2022 at 2:59 AM Lijun Dong <[e-mail]> wrote:
> 
> > Hi dispatch:
> >
> >
> >
> > I want to share my recently submitted draft on “Discarding Priority of RTP
> > Video Packets”.
> >
> >
> >
> > https://datatracker.ietf.org/doc/draft-dong-priority-rtp-packet/
> > <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-dong-priority-rtp-packet%2F&data=05%7C01%7Clijun.dong%40futurewei.com%7Cf4f099e6e73948d8ec8b08da645f3cd2%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637932657449689304%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Z1%2BLmuaJWeZHd6TIDI%2F0o3ukSdRXRNi8oZb1hKaxYro%3D&reserved=0>
> >
> >
> >
> > It is observed that significance difference or discarding priority might
> > exist among RTP packets which encapsulate video streaming data with the
> > existing modern video codecs. So selectively dropping RTP packets according
> > to their significances could be a complementary mechanism when dealing with
> > network congestion and improve end user’s QoE. The draft proposes that the
> > video source or edge node with media-awareness could perform mapping of RTP
> > packet discarding priority carried in RTP NALU header to a DSCP value, such
> > that the priority-based dropping could happen at the packet level when
> > network congestion happens.
> >
> >
> >
> > I look forward to your generous comments and suggestions.
> >
> >
> >
> > Lijun
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > dispatch mailing list
> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/dispatch
> >

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