[gentoo-server] Relatively recent guide on TCP congestion-avoidance algo's & traffic shaping

[Pandu Poluan <pandu@poluan.info>]

Can't sleep much last night due to the baby's quirky sleep pattern, so
been spending the night reading about TCP congestion avoidance
algorithms [1] -- and bufferbloat [2].

So, here's a spark of what (I hope) could be a starter for a deep
discussion for us sysadmins/netadmins. (Which is why I decided to post
in the -Server list).

I've been, um, enjoying bandwidth beyond what I should be
experiencing, by extensively tuning the TCP buffers (among others,
increasing its max-size to, like, um, 16MB) and using a non-default
congestion avoidance algo (namely, H-TCP). However, reading the
article from Jim Getty about bufferbloat made me re-think my setup.

Another factor that made me re-think my setup is the 'strange'
characteristics of traffic between my office and our
brand-spankin'-new subsidiary office 14 floors below us: SSH is very
nice, but any big file transfers (sftp, http, ftp, cifs, *anything*
biggish) will run well only for the first 10 seconds or so, before
slowing to a crawl (and even managed to make WinSCP complaining of 'no
response for 15 seconds'). But the ping's have no dropped packets at
all.

Oh, and this slowdownishness also affects some app in the sub office
which connects to the MS SQL Server @ HQ.

I'm in a bit of quandary; my bandwidth may be ill-gotten, but
employees (and the Management) enjoy the current performance. But,
then again, connection between HQ and Sub is flakey.

Reading more on the comments given in [2], I had thought that traffic
shaping -- at least between HQ and Sub -- may be the solution. And I
might alleviate the interconnection pressure somewhat by changing to a
different algo.

Unfortunately, howto's and guides re: traffic shaping and TCP
cong-algo that I can find using GooBing seems... outdated.

So, some questions popped into my head:

1. Is there a quite-recent and near-up-to-date guide to traffic
shaping and/or TCP cong-algo?

1a. Any analisis on the pro's/con's of H-TCP vs CUBIC vs Westwood+ vs
(insert some exotic-but-available cong-algo here)?

2. Am I experiencing and/or causing and/or contributing bufferbloat?

3. What else could explain the peculiar traffic characteristics
between my HQ and my sub-office?

3a. Will egress traffic shaping help?

Any thoughts are welcome. This thread is open for discussion.

And forgive me if I write somewhat incoherently; I'm yet to finish my
first cup of coffee.

[1] http://www.google.com/m?client=ms-opera-mini&channel=new&q=linux+tcp+congestion+avoidance+algorithm&spell=1&ei=wxYNTpjZM6eViAKkpfSCAg&ved=0CAQQvwUoAA

[2] http://gettys.wordpress.com/2010/12/06/whose-house-is-of-glasse-must-not-throw-stones-at-another/

Rgds,


-- 
--
Pandu E Poluan - IT Optimizer
My website: http://pandu.poluan.info/