Re: slow tcp on 100mbps wan, strange tcp window behaviour on ubuntu 9.10

[Andres Meyer <andres.meyer@xxxxxxxxxxxx>]

On Thu, 2010-03-11 at 00:59 +0100, Andres Meyer wrote:
> On Wed, 2010-03-10 at 15:49 -0800, Stephen Hemminger wrote:
> > If you use tcptrace to produce xplot graphs of sequence number,
> > you get the attached result.  The upper line is the sequence number
> > of the upper bound of the window.
> > 
> > It shows the window for the sender is open but is not being used.
> > This means the send window is not configured large enough on the sender.
> > With current Linux kernels, you should not have to configure socket
> > send buffers in the application.  It maybe that the application is
> > using setsockopt to set send buffer space but not allowing for enough window.
> 
> Thank you for the tip. I also studied this graph (and others) before
> posting. I thought the same thing in the beginning, so I tried setting
> the settings in the /proc/sys/net/ipv4 region in the kernel. I tried
> with iperf and netcat. I even set the window with the -w option to
> 1Mbyte in iperf (client and server), just to see if something would
> change, but nothing did. Do you know another program that for sure does
> not use this setsockopt for testing?

I also tried with wget (client) and apache2.2 (server), same effect.

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