[Bloat] About LEDBAT, µTP and BitTorrent

[Juliusz Chroboczek <jch@pps.jussieu.fr>]

Hi,

In his series of articles, Jim has mostly been concerned about
router-based solutions to the delay issues.  As you know, people have
also been working on end-to-end solutions, mostly within the framework
of TCP (people have already mentioned TCP-Vegas on this list).  There's
a couple things I'd like to add.

Linux allows switching congeston controllers on the fly.  I've used this
in the Transmssion BitTorrent client, which is now able to use TCP-LP (a
less aggressive variant of Vegas) on a system that uses the default
congestion controller for other TCP connexions [1].

Of particular notice is the LEDBAT congestion controller [2], which, to
my knowledge, is the only congestion controller that was explicitly
designed to bound delay [3].  It is also the only delay-besed controller
that has been deployed on a massive scale -- all recent versions of
µTorrent use LEDBAT by default.  If you'd like to experiment with LEDBAT
under Linux, I've recently ported the µTorrent code to Transmission [4],
and I'm told it's also in KTorrent and libtorrent.

I'd love to see LEDBAT in the Linux kernel, and I know people who'd love
to see it in Windows.  If you'd like to either do the work or fund it,
please do get in touch.

--Juliusz

[1] http://www.pps.jussieu.fr/~jch/software/bittorrent/tcp-congestion-control.html
[2] http://datatracker.ietf.org/wg/ledbat/charter/
[3] http://forum.bittorrent.org/viewtopic.php?pid=762#p762
[4] https://forum.transmissionbt.com/viewtopic.php?f=1&t=11130