[tsvwg] Comments on draft-ietf-tsvwg-ecn-l4s-id-05

[Ingemar Johansson S <[e-mail]>]

Hi

 

I have read through draft-ietf-tsvwg-ecn-l4s-id-05 and here are a few comments: 

 

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Section 4.2:

 

QUIC : QUIC has ECN support from v1. This is described in https://tools.ietf.org/html/draft-ietf-quic-transport-16 , the implemented ECN counters in the draft supports L4S. As of today however only classic ECN handling is described in https://tools.ietf.org/html/draft-ietf-quic-recovery-16. 

 

RMCAT : The generic feedback format draft https://tools.ietf.org/html/draft-ietf-avtcore-cc-feedback-message-02 supports ECN marking that can be used with L4S. RFC8298 (SCReAM) currently only specifies classic ECN handling, but running code of SCReAM found at https://github.com/EricssonResearch/scream has a working L4S implementation.

 

In both examples above, L4S support is almost there, I am not however sure if that is good enough to be included in the L4S ID draft ?

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Section 4.3:

This one caught my attention “A scalable congestion control MUST react to ECN marking from a

      non-L4S but ECN-capable bottleneck in a way that will coexist with

      a TCP Reno congestion control [ <https://tools.ietf.org/html/rfc5681> RFC5681] (see  <https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#appendix-A.1.4> Appendix A.1.4 for

      rationale).

After reading the appendix I do agree with the intention, it can however be a challenge to realize this but you have perhaps a solution to this problem already in the chirped CC ?. Also it is possible that BBR v2 may satisfy this requirement but sofar it is merely speculation.

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A.1.6.  Scaling down to fractional congestion windows

Perhaps a silly question. Can packet pacing be exploited for this purpose ? So instead of a sub MSS congestion window you set the pacing rate to a value lower than (MSS*8)/RTT ? The challenge is of course the proper calculation of the pacing rate.

 

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Otherwise I don’t have any objections 

 

Regards

Ingemar Johansson

==================================

Ingemar Johansson  M.Sc. 

Master Researcher

 

Ericsson Research

Network Protocols & E2E Performance

Labratoriegränd 11

971 28, Luleå, Sweden

Phone [phone]

SMS/MMS [phone]

 <mailto:[e-mail]> [e-mail]

www.ericsson.com

 

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==================================

 

 

From: Bob Briscoe <[e-mail]> 
Sent: den 8 november 2018 05:55
To: Ingemar Johansson S <[e-mail]>
Subject: L4S Review from mobile and RMCAT viewpoint?

 

Ingemar,

Pref. before the end of Nov. could you review at least one of the L4S drafts, cc the [e-mail] <mailto:[e-mail]>  list? To check we're not precluding anything from an RMCAT or LTE viewpoint.
We've finished the text of all 3 L4S drafts, apart from a couple of very minor ToDo's so it's all stable now.

The chairs will be going to WGLC in Jan, or in mid-Dec if sufficient reviews already then.

*	at least the L4S Identifier draft <https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id> , which gives amongst other things:

*	the prerequisites a transport must comply with before sending ECT(1) [thinking particularly from RMCAT and QUIC perspectives]
*	relation with other identifiers (e.g. Diffserv),

*	possibly also the DualQ AQM draft <https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled>  (focus on the short Functional and Management Requirements section, where all the MUSTs are) [from LTE implementation perspective]

Cheers, and thank you in advance


Bob

PS. The 3rd primary L4S draft going through now is the architecture, but others are reviewing that.






-- 
________________________________________________________________
Bob Briscoe                               http://bobbriscoe.net/