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Thread ID: 24493 2002-09-12 08:01:00 Linux TCP/IP tuning over DSL sprog (1862) Press F1
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78864 2002-09-12 08:01:00 Just upgraded our Linux firewall from a P75 to an Athlon 1800, and surprisingly our downloads have increased from 25k to 250k! I wonder if this is to be expected or has there been a coincidental Telecom upgrade... I have other sites on P166s which have 70k downloads, can I tune TCPIP on these Debian machines or is it simply PC speed or coincidence? sprog (1862)
78865 2002-09-14 00:10:00 > Just upgraded our Linux firewall from a P75 to an
> Athlon 1800, and surprisingly our downloads have
> increased from 25k to 250k! I wonder if this is to
> be expected or has there been a coincidental Telecom
> upgrade . . . I have other sites on P166s which have
> 70k downloads, can I tune TCPIP on these Debian
> machines or is it simply PC speed or coincidence?

There are several reasons why this might have happened .

First, the new hardware . Although a Pentium 75 is more than enough to handle 10Mbps network traffic, a more powerful CPU, better NIC, faster bus, etc . obviously does it much better .

Second, you might have installed a newer Linux kernel with RFC 1323 TCP options enabled . This gives you Large TCP Windows, which is what you need for a fat pipe with relatively high latency .

In the newer 2 . 4 Linux kernels, the TCP/IP stack is more or less auto-tuning . It scales the TCP send and receive buffers up to 128KB, for instance . The only you need to check is if your particular distribution enables useful features like the above RFC 1323 TCP options .

You might find that upgrading the Linux distribution on the Pentium 166s will boost performance for this reason . However, do some testing first, to see if you can find out what the connection is like, (check round trip times, packet loss, even stuff like whether or not the NIC is running at full-duplex) .

--
Juha
juha (761)
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