Re: [rmcat] [tsvwg] FW: Fwd: Submitted ID on delay vs. loss-only rate-adaptive for DiffServ

["Cheng-Jia Lai (chelai)" <[e-mail]>]

I think it would be good if Section 5.1 can include some specification or recommendation how a video flow's packets should be classified into CS4 and CS4-Discardable and how they will be dropped preferentially at congestion. Although AF4x has already specified how to do this by different drop probabilities, it might not be suitable since I-frame, IDR, or other important packets (e.g. in-band signals or supplementary metadata) can still be dropped by probability (smaller though) before all discardable P frames in the same video flow are dropped.

In addition, maybe it should cover some fairness requirements, i.e. how the video rate adaptive behaviors can expect to see packet drops w.r.t. contention, which IMHO should encourage video endpoints to generate more discardable P-frame or other lower priority packets, even at congestion. If possible, this should also try to avoid global synchronization, i.e. all video-encoders to generate I-frame/IDR at the same time (even after they reduce rate, they still need to recover the lost video) when CS4 / CS4-Discardable queue is congested and drops packets from all of them.

Regards,
CJ


-----Original Message-----
From: James Polk (jmpolk) 
Sent: Tuesday, July 16, 2013 2:11 PM
To: Cheng-Jia Lai (chelai); James Polk (jmpolk); Toerless Eckert (eckert); Michael Ramalho (mramalho); [e-mail]; [e-mail]
Subject: RE: [tsvwg] FW: [rmcat] Fwd: Submitted ID on delay vs. loss-only rate-adaptive for DiffServ

CJ

Thank you for the quick review.

I'll ask you the same question I just asked Michael, the draft isn't 
very long (under 8 pages currently), and it is a work in progress - 
but do you have text or just points that this draft needs to cover 
that it doesn't currently?

James

At 01:36 PM 7/16/2013, Cheng-Jia Lai (chelai) wrote:
>Same here... I feel it makes sense to create a new DSCP / CS4 for 
>transport of video flows that have rate adaptive behaviors and/or 
>intra-flow preferential drop priorities as indicated in the I-D. The 
>service provided by the network may thus be considered new, i.e. 
>different from what exists in AF4x, so IMHO, using a new or reusing 
>CS4 service class adds clarity for the user applications.
>
>Regards,
>CJ
>
>
>-----Original Message-----
>From: [e-mail] [mailto:[e-mail]] On 
>Behalf Of Michael Ramalho (mramalho)
>Sent: Tuesday, July 16, 2013 6:36 AM
>To: [e-mail]
>Subject: [tsvwg] FW: [rmcat] Fwd: Submitted ID on delay vs. 
>loss-only rate-adaptive for DiffServ
>
>TSVWG Members,
>
>I should have copied you on my email to the RMCAT mailer below.
>
>I strongly support the creation of a new DSCP for transports in 
>which their congestion control can adapt based on delay.
>
>The current ID in support of this 
>(http://www.ietf.org/internet-drafts/draft-polk-tsvwg-delay-vs-loss-ds-service-classes-00.txt 
>) is a work in progress, but a step in the right direction.
>
>It is a given that the ability of the eventual RMCAT adaptation 
>mechanisms to achieve low delay will be function of the other 
>dominant traffic it is competing against. If the dominant competing 
>traffic DEPENDS on loss, the RMCAT packets are held hostage to being 
>delayed by the bottleneck queue delay maximum.
>
>Thus, whenever possible, it will be preferable for RMCAT flows to 
>compete with other congestion control transports that adapt on 
>delay. Even this may not get us to the desired low-delay goals when 
>a portion of the traffic has long RTTs (i.e., adaptation control 
>loops that are long in time), or for links that have a highly-time 
>varying capacity,  but it will help for a lot of common bottleneck 
>topologies (e.g., slowly time-varying access bufferbloat).
>
>It is my hope that this topic has some discussion time in the Berlin 
>Transport WG (not the specific codepoint to be chosen, but rather 
>the need for one).
>
>Off Soapbox,
>
>Michael Ramalho, Ph.D.
>
>-----Original Message-----
>From: Michael Ramalho (mramalho)
>Sent: Tuesday, July 16, 2013 9:06 AM
>To: [e-mail]
>Subject: RE: [rmcat] Fwd: [tsvwg] Submitted ID on delay vs. 
>loss-only rate-adaptive for DiffServ
>
>RMCAT Design Team,
>
>The draft Lars references below is a formal request for a DSCP 
>dedicated to "RMCAT-only (or other nice delay-based cc) traffic".
>
>It will take a while to become socialized ... and we can progress 
>our RMCAT work in the interim.
>
>Michael Ramalho
>
>-----Original Message-----
>From: [e-mail] [mailto:[e-mail]] On 
>Behalf Of Eggert, Lars
>Sent: Tuesday, July 16, 2013 5:26 AM
>To: WG WG
>Cc: [e-mail]
>Subject: [rmcat] Fwd: [tsvwg] Submitted ID on delay vs. loss-only 
>rate-adaptive for DiffServ
>
>Possibly of interest to RMCAT.
>
>Begin forwarded message:
>
> > From: James Polk <[e-mail]>
> > Subject: [tsvwg] Submitted ID on delay vs. loss-only 
> rate-adaptive for DiffServ
> > Date: July 16, 2013 8:07:59 GMT+02:00
> > To: <[e-mail]>
> >
> > (as an author)
> >
> > Toerless and I put together a draft about legacy rate-adaptation 
> based only on loss vs. what RMCAT is looking to (for RTCWEB), which 
> is based on delay and loss.  Here's the URL.
> >
> > 
> http://www.ietf.org/internet-drafts/draft-polk-tsvwg-delay-vs-loss-ds-service-classes-00.txt
> >
> > It's more raw than we had in mind, but we believe this is 
> necessary, based on implementation experience and what users and 
> customers have in their networks, or are planning on having in 
> their networks soon.
> >
> > James & Toerless
> >