RE: tsv-dir review of draft-ietf-mptcp-congestion-05

2011-07-21 Thread david.black 
Costin,

The proposed -06 version sufficiently clarifies my one open issue.

I agree that the NSDI paper is an important citation and did not intend to
suggest that it be removed.  In addition, your decision to not cite RFC 3124
is ok with me.

Thank you for responding to the review.

Thanks,
--David

David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953 FAX: +1 (508) 293-7786
david.bl...@emc.com    Mobile: +1 (978) 394-7754


 -Original Message-
 From: Costin Raiciu [mailto:c.rai...@cs.ucl.ac.uk]
 Sent: Tuesday, July 19, 2011 12:35 PM
 To: Black, David
 Cc: tsv-dir; tsv-area; ietf; m.handley; d.wischik; multipathtcp
 Subject: Re: tsv-dir review of draft-ietf-mptcp-congestion-05
 
 Hi David,
 
 Thank you for your review.
 
  Major:
 
  I have one open issue - the first two goals (in the Introduction) are to 
  have multipath
  TCP connections behave somewhat like single-path connections in terms of 
  effects on
  (fairness to) other traffic.  The algorithm specified accomplishes this 
  solely by
  coupling the additive increase functionality across the flows, but allowing 
  each flow
  to react to drops and congestion separately (no decrease coupling).  The 
  draft does
  not explain why increase coupling alone is sufficient to achieve these 
  goals or what
  compromise to the goals results from only coupling increases.
 
 Our proposal fully achieves goals 1 and 2 - fairness to single path tcp  and 
 improve throughput. It
 does not fully achieve goal three - balancing congestion; fully achieving 
 goal 3 is very difficult,
 and an explanation is attempted in section 5; a reference is given to the 
 NSDI paper for further info.
 
  Section 5 is a good start on this discussion, but it's not clear about what 
  compromises
  to the goals results from increase coupling only.  Section 5 criticizes an 
  alternative
  that couples both increases and decreases for failing to achieve Goal 1, 
  but doesn't
  say what this approach achieves.  At most a few additional sentences in 
  Section 5 should
  suffice to address this concern, and Section 2 should be edited to align 
  with the
  changes to Section 5.
 
 We have updated section 5 to make these points clear - they weren't clear 
 enough before.
 
  Minor:
 
  While the [NSDI] paper is a fine place to reference work published in 
  conferences
  and/or journals, RFC 3124 on the Congestion Manager is related IETF work 
  and should
  be cited here as an Informative Reference.
 
 The congestion manager is indeed related work and should be cited in a 
 research paper, but does not
 help understanding the congestion controller presented in this draft. We 
 chose not to cite it
 explicitly.
 
 We chose to cite the NSDI paper because it describes in detail the design 
 choices that shaped the
 algorithm, and it will help an interested reader understand more about the 
 algorithm.
 The discussion section is itself a short high level summary of those 
 decisions.
 
 We attach the new version of this draft to this email (we cannot post a new 
 version online of the
 draft because the IETF submission cutoff date has passed). Could you please 
 check the draft and see if
 the issues you raised have been clarified?
 
 We will post the draft as soon as submissions reopen after the IETF
 
 Thanks,
 Costin
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tsv-dir review of draft-ietf-mptcp-congestion-05

2011-07-05 Thread david.black 
I've reviewed this document as part of the transport area directorate's ongoing
effort to review key IETF documents. These comments were written primarily for 
the
transport area directors, but are copied to the document's authors for their
information and to allow them to address any issues raised. The authors should
consider this review together with any other last-call comments they receive.
Please always CC: tsv-...@ietf.org if you reply to or forward this review.

Summary:

This draft is on the right track but has open issues, described in the review.

Comments:

This draft specifies the congestion control modifications for multi-path TCP.

Major:

I have one open issue - the first two goals (in the Introduction) are to have 
multipath
TCP connections behave somewhat like single-path connections in terms of 
effects on
(fairness to) other traffic.  The algorithm specified accomplishes this solely 
by
coupling the additive increase functionality across the flows, but allowing 
each flow
to react to drops and congestion separately (no decrease coupling).  The draft 
does
not explain why increase coupling along is sufficient to achieve these goals or 
what
compromise to the goals results from only coupling increases.

Section 5 is a good start on this discussion, but it's not clear about what 
compromises
to the goals results from increase coupling only.  Section 5 criticizes an 
alternative
that couples both increases and decreases for failing to achieve Goal 1, but 
doesn't
say what this approach achieves.  At most a few additional sentences in Section 
5 should
suffice to address this concern, and Section 2 should be edited to align with 
the
changes to Section 5.

Minor:

While the [NSDI] paper is a fine place to reference work published in 
conferences
and/or journals, RFC 3124 on the Congestion Manager is related IETF work and 
should
be cited here as an Informative Reference.

idnits 2.12.12 didn't find any nits.

Thanks,
--David

David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953 FAX: +1 (508) 293-7786
david.bl...@emc.com    Mobile: +1 (978) 394-7754



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