On 05/14/2012 11:30 AM, Juliusz Chroboczek wrote:
I think, but am not certain, jch is referring to the problem of
negotiating ecn over uTP.
No, I was actually unaware that Linux allows one to set the ECN bits
from userspace.
It's also possible to get them from userspace.
OTOH, you're right that µTP doesn't currently support ECN. Not that it
matters much, ECN is useful for interactive connections (where it can
avoid a one-RTT delay due to a packet loss) but pretty useless for bulk
transfers[1].
My scenario is that AQM isn't just for routers anymore.
On a related note, the µTP framing is pretty horrible IMHO, and LEDBAT
is better implemented within TCP. Unfortunately, this is not possible
under Windows (yeah, I got one of the µTorrent guys to contact Microsoft
on this subject).
On a note related to the related note, Transmission already has the
ability to make use of a non-default congestion controller for TCP:
http://www.pps.jussieu.fr/~jch/software/bittorrent/tcp-congestion-control.html
TCP_LEDBAT has been in cerowrt for months. Haven't played with it much, was
mostly comparing westwood and cubic.
http://perso.telecom-paristech.fr/~valenti/pmwiki/pmwiki.php?n=Main.LEDBAT
Also have the ability to exercise alternate algorithms in the latest
netperf in svn
(as well as classification).
-- Juliusz
[1] Marek Malowidzki, Simulation-based Study of ECN Performance in RED
Networks, In Proc. SPECTS'03. 2003.
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