[pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)

Eugen Leitl eugen at leitl.org
Tue Jun 28 08:52:55 UTC 2011

----- Forwarded message from William Salt <williamejsalt at googlemail.com> -----

From: William Salt <williamejsalt at googlemail.com>
Date: Tue, 28 Jun 2011 08:03:25 +0100
To: support at pfsense.com
Subject: [pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)
Reply-To: support at pfsense.com

Hi All,
         For the last couple of months i have been pulling my hair out
trying to solve this problem.
We have a 1Gbps transatlantic link from the UK to the US, which has
successfully passed the RFC2544 test.

At either end, we have a media converter, and a supermicro server with an
intel quad port NIC running pfsense 2 (RC2 at one end RC3 at the other) and
the IGB driver on the quad port.

We can pass 1gbps either way with UDP. However we are experiencing very
strange issues with tcp connections.

With window scaling enabled, and a max socket buffer set to 16MB, we see no
Even disabling window scaling and setting the window to 16MB makes no

Each TCP connection starts very slowly, and will max out at around 190mbps,
taking nearly 2 minutes to climb to this speed before *plateauing*.

We have to initiate many (5+) connections to saturate the link with tcp
connections with iperf.

Real world tests transferring files, max out at 100mbps, using multiple

I have followed guides like this:

With no luck, and have tweaked, disabled, and enabled nearly every relevant
sysctl parameter with no luck.

Can anyone shed some light on this?

I am now doubting the IGB driver, and am looking to swap out the cards as a
last ditch effort.
However, we have tried different hardware (L3 switches, media convertes +
laptops etc), and the symptoms still persist...
The only constant is freebsd 8.1 - pfsense (or 8.2 for our production
I have tried the freebsd net mailinglist, but im hoping you lot can help me!

Cheers in advance

----- End forwarded message -----
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org
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