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-dir(_at_)ietf(_dot_)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(_dot_)black(_at_)emc(_dot_)com Mobile: +1 (978) 394-7754
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