Re: [tcpPrague] FW: I-D Action: draft-black-tsvwg-ecn-experimentation-00.txt

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

Hi

Comments inline [IJ]

> -----Original Message-----
> From: Black, David [mailto:[e-mail]]
> Sent: den 7 oktober 2016 02:28
> To: Ingemar Johansson S <[e-mail]>;
> [e-mail]; [e-mail]; [e-mail]
> Cc: Black, David <[e-mail]>
> Subject: RE: [tcpPrague] FW: I-D Action: draft-black-tsvwg-ecn-
> experimentation-00.txt
> 
> Hi Ingemar,
> 
> David> Inline
> 
> Thanks, --David
> 
> > -----Original Message-----
> > From: Ingemar Johansson S [mailto:[e-mail]]
> > Sent: Thursday, October 06, 2016 4:32 AM
> > To: Black, David; [e-mail]; [e-mail];
> > [e-mail]
> > Cc: Ingemar Johansson S
> > Subject: RE: [tcpPrague] FW: I-D Action:
> > draft-black-tsvwg-ecn-experimentation-
> > 00.txt
> >
> > Hi
> >
> > Thanks for writing up this draft. I have some comments on the contents
> 
> Thanks for carefully reading the draft.
> 
> > Intended status : Standards track. I interpret this that it means that
> > this document becomes standards track.
> > Are there any ideas around the intended status for a document such as
> > briscoe- tsvwg-ecn-l4s-id, will it be experimental first or ?
> 
> Possibly - I don' t know.  The ecn-experimentation draft is not intended to
> settle that question for the l4s-id draft or any of the other drafts involved in
> the described areas of experimentation.
> 
> I wrote the ecn-experimentation draft to allow the experiments to be
> specified in Experimental RFCs without each experiment also needing a
> companion Standards
> Track RFC just to open up space for the experiment.   If any of the
> experiments
> pan out so well that they deserve to be immediately written up as a
> Standards Track RFC without bothering with an Experimental RFC, then that
> would be wonderful, IMHO.
> 
> > Section 4.2 : " "Unless otherwise specified by an Experimental RFC, routers
> treat
> >       the ECT(0) and ECT(1) codepoints as equivalent, and senders are
> >       free to use either the ECT(0) or the ECT(1) codepoint to indicate
> >       ECT, on a packet-by-packet basis.""
> > In some way I find it to contradict the proposed statement in  section 3 "
> > Protocols and senders that only require a single ECT codepoint  SHOULD
> > use ECT(0)."
> > I see here a risk that the statement in 4.2 can delay deployment of
> > L4S capability based on the use of ECT(1) in the networks ?
> 
> My understanding is that L4S requires both ECT(0) and ECT(1), as it couples
> treatments of traffic marked with those codepoints.  For that reason, the
> statement in section 3 (which is quoted from RFC 3168) does not apply to L4S.
[IJ] It is perhaps here I see things differently. 
My interpretation is that L4S is that senders mark packets with some special codepoint (let's call it ECT(1) ) and network queues detect this and send the packets to a dedicated queue which marks these packets to ECN-CE at a very low queue delay. A special case may be that senders are networks are 100% L4S (Data centers), this means that only the code point ECT(1) is in use.
The handling of ECT(0) and not-ECT packets goes outside the L4S definition and definitely requires dualQ solution and classification. 
It is quite possible that my interpretation is flawed. 

> 
> OTOH, I see your concern, namely that "free to use" in the RFC 3168 text
> quoted in 4.2 is somewhat at odds with "SHOULD use ECT(0)" in the RFC 3168
> text quoted in section 3.  This is a concern with RFC 3168 itself.
> 
> Would it help for this ecn-experimentation draft to update RFC 3168 by
> removing the words "and senders are free to use either the ECT(0) or the
> ECT(1) codepoint to indicate ECT, on a packet-by-packet basis."  ?
[IJ] Yes, it probably solves things, mind though that reason why I brought this is up is that I may interpret the definition of L4S differently.

> 
> > Section 5 : I see the main problem with RFC6679 (in this context) in
> > the use of the nonce. Don't however see any major problem to use
> > feedback also for an L4S capable sender/receiver using ECT(1).
> > For that purpose it may be better to rewrite :
> >       Use of ECT(1) and random ECT values is discouraged, as that may
> >       expose RTP to differences in network treatment of ECT(1) and
> >       ECT(0), e.g., as proposed in [I-D.briscoe-tsvwg-ecn-l4s-id].
> > To :
> >       Use of ECT values is discouraged, as that may
> >       expose RTP to differences in network treatment of ECT(1) and
> >       ECT(0), e.g., as proposed in [I-D.briscoe-tsvwg-ecn-l4s-id].
> 
> Good point - I agree.  I would insert "random" after "Use of" in the "To:" text.
> I'll make that change in my working copy that will become -01.
> 
> > Further ... quote " In support of Alternative Backoff experimentation
> > ...". I would say that this applies to L4S as well. As an example,
> > SCReAM (RMCAT WG congestion control candidate) is easily modified to
> > support L4S, and the RFC6679 feedback can be used with SCReAM. For
> > that reason it may be better to rephrase it like " In support of
> > Alternative Backoff experimentation and experiments based on
> > [I-D.briscoe-tsvwg-ecn-l4s-id]....." or something similar
> 
> I'd prefer to do something different.   I think L4S is an example of both the
> Alternative
> Backoff and ECT Differences areas of experimentation, and hence I'd suggest
> citing an L4S draft in the description of the Alternative Backoff experiment
> scope in Section 2.  Which L4S draft would you suggest?
[IJ] Good question.. Not sure what is required here?. Our proprietary SCReAM research code has support for L4S, one possibility is to update the SCReAM draft with a description of this functionality. An example was shown at the L4S BoF (page 6-7 in https://www.ietf.org/proceedings/96/slides/slides-96-l4s-2.pdf )

> 
> >
> > Regards
> > /Ingemar
> >
> > > -----Original Message-----
> > > From: Black, David [mailto:[e-mail]]
> > > Sent: den 1 oktober 2016 00:42
> > > To: [e-mail]; [e-mail]; [e-mail]
> > > Cc: Black, David <[e-mail]>
> > > Subject: [tcpPrague] FW: I-D Action:
> > > draft-black-tsvwg-ecn-experimentation-
> > > 00.txt
> > >
> > > This is the process-oriented draft on ECN experimentation that I
> > > promised at the TSVWG
> > > meeting in Berlin.   Comments are welcome, but please keep the process
> > > focus in mind -
> > > the intent is to leave documentation of the actual ECN changes and
> > > rationale to the referenced drafts that document the ECN experiments.
> > >
> > > Thanks, --David
> > >
> > > -----Original Message-----
> > > From: I-D-Announce [mailto:[e-mail]] On Behalf
> > > Of [e-mail]
> > > Sent: Friday, September 30, 2016 6:24 PM
> > > To: [e-mail]
> > > Subject: I-D Action: draft-black-tsvwg-ecn-experimentation-00.txt
> > >
> > >
> > > A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> > >
> > >
> > >         Title           : Explicit Congestion Notification (ECN) Experimentation
> > >         Author          : David Black
> > > 	Filename        : draft-black-tsvwg-ecn-experimentation-00.txt
> > > 	Pages           : 10
> > > 	Date            : 2016-09-30
> > >
> > > Abstract:
> > >    Multiple protocol experiments have been proposed that involve
> changes
> > >    to Explicit Congestion Notification (ECN) as specified in RFC 3168.
> > >    This memo summarizes the proposed areas of experimentation to
> provide
> > >    an overview to the Internet community and updates RFC 3168, a
> > >    Proposed Standard RFC, to allow the experiments to proceed without
> > >    requiring a standards process exception for each Experimental RFC to
> > >    update RFC 3168.  This memo also makes related updates to the ECN
> > >    specification for RTP in RFC 6679 for the same reason.  Each
> > >    experiment is still required to be documented in an Experimental RFC.
> > >    This memo also records the conclusion of the ECN Nonce experiment in
> > >    RFC 3540, obsoletes RFC 3540 and reclassifies it as Historic.
> > >
> > >
> > > The IETF datatracker status page for this draft is:
> > > https://datatracker.ietf.org/doc/draft-black-tsvwg-ecn-experimentati
> > > on/
> > >
> > > There's also a htmlized version available at:
> > > https://tools.ietf.org/html/draft-black-tsvwg-ecn-experimentation-00
> > >
> > >
> > > Please note that it may take a couple of minutes from the time of
> > > submission until the htmlized version and diff are available at
> tools.ietf.org.
> > >
> > > Internet-Drafts are also available by anonymous FTP at:
> > > ftp://ftp.ietf.org/internet-drafts/
> > >
> > > _______________________________________________
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> > >