Subject: [tsvwg] Alissa Cooper's Yes on draft-ietf-tsvwg-diffserv-intercon-12: (with COMMENT)

From: "Alissa Cooper" <[email-masked]>
Date: Thu, 01 Dec 2016 06:26:49 -0800

Alissa Cooper has entered the following ballot position for
draft-ietf-tsvwg-diffserv-intercon-12: Yes

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COMMENT:
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Thanks for writing this document.

One thing I didn't get is why not have a fifth aggregate that CS1 could
be mapped into. Is it just because in other standards that have specified
aggregates like this, they've gone with four and not specified one for
less-than-best-effort?

I'm also wondering about the choice to reserve AF42 and AF43. For WebRTC
and real-time applications (see table at
https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18#section-5)
traffic marked as "Medium" in the table would be treated the same as
"Low," which I fear would give incentives for applications to mark their
traffic as "High" instead. Unless there is a strong need to reserve AF42
and AF43, it might be nice to just include them.

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From: "Black, David" <[email-masked]>
Date: Thu, 1 Dec 2016 15:32:22 +0000

Alissa,

> aggregates like this, they've gone with four and not specified one for

Available MPLS label space considerations (i.e., lack of space) are a major
reason to limit the number of aggregates to four, and RFC 5127 did
likewise for similar reasons.

Beyond that, there is no longer IETF consensus that CS1 should be used for
the traffic class variously known as Lower Effort, less-than-best-effort or
scavenger, see: https://datatracker.ietf.org/doc/draft-ietf-tsvwg-le-phb/ .

> and AF43, it might be nice to just include them.

Well, that rtcweb-qos draft uses 11 DSCPs, so there are a number of distinctions
that have to be lost in order to get to 4 traffic aggregates.  In contrast to AF33,
which is reserved by this draft, the text on AF42 and AF43 is weaker:

          The AF42 and AF43 PHBs could be added if there
           is a need for three-color marked Multimedia.

Are you asking for these two to be added now because WebRTC is expected to
make extensive use of two- and three-color marking (e.g., of video streams)?

Thanks, --David

> -----Original Message-----
> From: Alissa Cooper [mailto:[email-masked]]
> Sent: Thursday, December 01, 2016 9:27 AM
> To: The IESG
> Cc: [email-masked]; Gorry Fairhurst; tsvwg-
> [email-masked]; [email-masked]; [email-masked]
> Subject: Alissa Cooper's Yes on draft-ietf-tsvwg-diffserv-intercon-12: (with
> COMMENT)
>

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From: Alissa Cooper <[email-masked]>
Date: Fri, 2 Dec 2016 13:34:56 -0500

Hi David,

> On Dec 1, 2016, at 10:32 AM, Black, David <[email-masked]> wrote:
> 
> Alissa,
> 

Got it, thanks for the explanation.

> make extensive use of two- and three-color marking (e.g., of video streams)?

Well, the expectation is that WebRTC implementations will make use of AF42 and AF43. I can’t predict how extensively.

Alissa