Date: Wed, 12 Nov 1997 11:33:27 +0100 (MET) From: Emmanuel Duros <Emmanuel.Duros@sophia.inria.fr> To: questions@freebsd.org Cc: Emmanuel.Duros@sophia.inria.fr Subject: rfc1323, cannot make it work! Message-ID: <199711121033.LAA11000@chouette.inria.fr>
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Hi,
I have two FreeBSD stations (A & B) interconnected by a 3.4MBps broadcast
satellite link. The RTT is about 330 ms. From A to B it takes 300ms and
from B to A 30 ms.
A runs FreeBSD 2.2.2-RELEASE and B runs 2.2.1-RELEASE.
The maximum data rate I can get when I download a big file is 50 Kbyte/s.
This is the maximum data rate I can reach with a 330ms RTT and a default
tcp windows size of 16kbytes -> In one seconde the server can send
16*(1/0.330) = 50 Kbyte/s. Every Ack beeing generated by the client every
330 ms.
According to rfc1323, increasing the size of the send and receive tcp
buffers we can normally obtain a much better data rate.
On both hosts A & B, I set net.inet.tcp.rfc1323 to 1 and
net.inet.tcp.{recv|send}space with values ranging from 16384 to
65536. With a 65Kbyte window we should theoritically get close to
200Kbyte/s
Using ftp and the netperf tool, I could not see any improvement
as far as the data rate is concerned.
Furthermore, whatever the value of rfc1323 (0 or 1) and even if I set
the size of tcp buffer to 4096, I still get a 50 Kbyte data rate?!?!?
I still have not understood why and I would appreciate any hint
on this!!!
Thanks
Emmanuel
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