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Network Performance Issues.



I have spent all day looking for clues as to how to debug network 
performance issues without success.  Nobody seems to answered my 
previous post on this subject - so I thought I would try again.

The problem I have is this.  I have a linux desktop (machine D) siting 
on a LAN in my home.  This is  connected to a linux firewall/nat router 
(machine S) with two ethernet cards.  One links out to the internet, 
the other connects to the internal lan.  Connections to the internet 
from machine D go through machine S, which acts as a NAT translation. I 
do all the control and firewalling using IPTABLES in machine S.

Downloading a video from youtube onto Machine D's desktop I get a 
download speed of about 7Kbytes/sec. Which is very low.  If I try to 
download the same one by ssh'ing into mahcine S and running wget on the 
same url, I get a download speed of 80Kbytes/sec (ie more than 10 times 
faster).

This would normally imply a bottle neck in the network between machines 
D and S. But if I download a similar file from machine S to machine D, 
then I get a throughput of about 11Mbytes/sec. 

I have do idea about how to debug this and find out what the problem is.  
Can someone here give me some clues as to what to do.
-- 
Alan Chandler
http://www.chandlerfamily.org.uk



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