Re: TCP performance on a lossy 1Gbps link

From: Randy Macleod
Date: Thu Dec 10 2009 - 16:46:31 EST


Mathew,

Matthew Hodgson wrote:
> I've got a dedicated 1000Mbps link between two sites with a rtt of 7ms,
> which seems to be dropping about 1 in 20000 packets (MTU of 1500 bytes).
> I've got identical boxes at either end of the link running 2.6.27
> (e1000e 0.3.3.3-k6), and I've been trying to saturate the link with TCP
> transfers in spite of the packet loss.

Sorry for the late reply...

If you just want to avoid the dramatic impact of dropped packets
due to something in the network getting overloaded,
you might consider:
http://www.gridmpi.org/pspacer-1.0/README.en.html

<quote>
PSPacer achieves precise network bandwidth control and smoothing of
bursty traffic without any special hardware. It is implemented as a
Linux loadable kernel module, i.e. a classful queuing discipline (Qdisc)
module available for traffic control with tc (8) command.

...
(2) PSPacer uses the IEEE 802.3x PAUSE frame as a gap between packets.

</quote>

Always seemed like a cool idea although I haven't tried it myself.

Hope this isn't too late to help.

// Randy


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