Date: Tue, 18 Dec 2007 13:55:20 +0100 From: Andre Oppermann <andre@freebsd.org> To: Lawrence Stewart <lastewart@swin.edu.au> Cc: James Healy <jhealy@swin.edu.au>, grenville armitage <garmitage@swin.edu.au>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Iccrg@cs.ucl.ac.uk, Randall Stewart <rrs@cisco.com>, tmrg-interest@ICSI.Berkeley.EDU, end2end-interest@postel.org, David Malone <David.Malone@nuim.ie>, Douglas Leith <Doug.Leith@nuim.ie>, Robert Shorten <Robert.Shorten@nuim.ie>, Larry Dunn <ldunn@cisco.com>, Fred Baker <fred@cisco.com> Subject: Re: Modular/Pluggable TCP Congestion Control for FreeBSD Message-ID: <4767C338.4070709@freebsd.org> In-Reply-To: <47675291.5070101@swin.edu.au> References: <47675291.5070101@swin.edu.au>
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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
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