[linux-dvb] Re: optimizing TCP transfers

[Philip Armstrong <phil@kantaka.co.uk>]

On Sun, Sep 29, 2002 at 11:16:02PM -0400, h018@ied.com wrote:
>   Can someone advise me please of the proper values for the variables in 
> /proc/sys/net/... ?
> 
>   Can someone point me please to a URL which would elaborate on the
> variables in the current kernels (2.4.x) to optimize TCP throughput under
> high latencies (800 - 2100 ms) ?

A quick google search reveals that everyone points to a page on
dslreports.com . Unfortunately dslreports.com is down, and google
hasn't cached the page.

However, I think your problem is that the max receive buffer size
under linux is only 64kB. Try increasing the value of
/proc/sys/net/core/rmem_max to say 131070 and see if that helps. You
may as well bump the default to the same value. If your bandwidth is
say 1Mbs, and the round trip time is a second or more, then you'll be
hitting the ceiling on the receive buffer within a second or so before
the first ack has a chance to get back. Worth a try anyway.

The other suggestions I've seen are to turn off tcp timestamps (echo
0 > /proc/sys/net/ipv4/tcp_timestamps) and to set the mtu on the
interface to a higher value to reduce the packet count.

Phil

-- 
http://www.kantaka.co.uk/ .oOo. public key: http://www.kantaka.co.uk/gpg.txt



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