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To:Gorry Fairhurst From:John Leslie Subject:Re: Note: WGLC Announcement for draft-ietf-tsvwg-byte-pkt-congest-07 Date:Fri, 30 Mar 2012 11:50:02 -0400
 

Gorry Fairhurst <gorry@erg.abdn.ac.uk> wrote:
>
> Please respond to the WGLC that ends on Friday 30th March 2012.
>
> Notes to the list would be helpful to complete the WGCC.

I cannot support this draft as written.

Perhaps some background would help...

It will be no secret to anyone following the ConEx WG that Bob and I
fundamentally disagree about whether to model congestion as per-packet
or per-byte. I strongly believe that it's packets that are congested, and
that we'll do better to accurately count congested packets than estimate
congested bytes; Bob seems to strongly believe that we'll do better to
estimate congested bytes than accurately count congested packets.

When I previously skimmed this document, I believed it contained only
common ground: that AQM should drop/mark packets without favoring small
packets, and that to whatever extent packet size _is_ considered, that
should be a transport-layer responsibility.

Alas, when I read it carefully this week, I find that Bob is actually
saying that transport-layer should _only_ consider "congested bytes", not
"congested packets".

In fact, Bob openly endorses replacing TCP congestion-control with an
algorithm which calculates "fair-share bytes" and doesn't back off at all
(even in the presence of 20% packet loss) unless you're already sending
more than this "fair-share".

I do not believe that is the consensus of this WG; and I believe if
that were the consensus it would exceed our charter.

The draft contains a number of things I _do_ support; and I'd be happy
to support a considerably shorter draft which concentrates on the AQM
recommendation, omitting any suggestions of modifying TCP congestion
control.

--
John Leslie <john@jlc.net>