Re: Modular/Pluggable TCP Congestion Control for FreeBSD

Rui Paulo
At Tue, 18 Dec 2007 13:55:20 +0100,
Andre Oppermann wrote:

Lawrence Stewart wrote:
Hi all,
We've been involved in a research project to implement and test an
emerging TCP congestion control algorithm under FreeBSD. As a part of
this, we've put together a patch for FreeBSD 7.0-BETA4 that modularises
the congestion control code in the TCP stack. It allows for new
congestion control algorithms to be developed as loadable kernel modules.
This improves FreeBSD's usefulness as a TCP research platform and
makes
it easier to customise the stack for specific scenarios like high
bandwidth, long delay paths.
There is an accompanying technical report "Light-Weight Modular
TCP Congestion Control for FreeBSD 7" [1] that covers the design,
features, kernel interface and usage of the framework. Also on our
website is
a beta release of a module that implements the H-TCP[2] congestion control
algorithm proposed by the Hamilton Institute.
We believe that modular congestion control is a worthwhile addition
to
FreeBSD. We've performed significant internal testing and there are
currently no known issues or regressions with the implementation
compared to a 'vanilla' FreeBSD 7.0-BETA4 kernel. We would welcome
further review and testing from the wider community in the hope of
getting this
patch folded into FreeBSD 8-CURRENT.
SIFTR [3], our tool for monitoring FreeBSD kernel TCP connection
state, has also
received a minor update to v1.1.5, with the addition of 6 new,
useful variables.
All code and documentation is available on our website[3].

I've started to completely overhaul tcp_input and tcp_output
including separating out the congestion control. Actually it
is similiar to the way you seem to do it.

A quick glance at your patch shows a couple of style issues
and a complete lack of locking.

Let me get you a Perforce account so we can develop and complete
this work together. I'll create a Perforce branch and import my
code and work in progress.

Andre, perhaps you could keep us, committers, more up to date with
your projects? I've been asked to port my NetBSD tcp_congctl(9) API to
FreeBSD at some point in time and I wasn't aware that you were working
on the same thing. Perhaps you could create a branch for you in p4 so
we could follow your work?

Thanks.
--
Rui Paulo
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