Network speed mysteries

[Andrew P.]

Dear friends

I have just stumbled upon a phenomena, which I cannot believe is real, 
though I reproduced it easily. Some days ago I have set up a 
FreeBSD-4.10 file-server. I have a small network in my room (3 boxes, 
100Mbps). I uploaded some files from my Windows 2000 PC, using the 
latest version of FileZilla client. The speed was pretty constant at 
9.5Mbytes/s. Two days ago I switched to Windows XP SP2, reinstalled all 
the software and was taken aback when I tried to upload some more files 
and the speed never exceeded 3.5Mb/s. I browsed and googled for some 
hours, made dozens of assumptions, tried to reconfigure both Windows and 
FreeBSD - but it was all in vain.

Just an hour ago I decided to rebuild the file-server kernel - and it 
takes time to build it there, as it's an old Celeron box with little 
RAM. By coincidence, some files were being uploaded just when I entered 
"make buildkernel ...". I looked at FileZilla windows, expecting to see 
the speed drop - but WOW! - the speed was at 7Mbytes/s!!! It then 
hovered around 6.5-9Mbytes/s while the kernel was being built! I waited 
for some minutes until the kernel was finally built - and the upload 
speed dropped back to 2.5-3.5Mb/s. I couldn't believe it - and I still 
can't - so I waited and built a kernel once more - with all the same 
effects on speed! It's worth to mention, that when I was installing the 
built kernel, the speed didn't change from usual 3Mb/s.

Please let me know what the heck is going on - or just what you think 
about it.

Best regards,
Andrew P.