From: John Beckett 

"Geo"  wrote in message
news::
> I wonder. All traffic going into the location where the news server is
> passes thru a packetshaper. I wonder if window scaling and the packet shaper
> are interacting?

Now that sounds a likely culprit.

I just saw in a previous message that you were wondering if maybe the MTU
was involved. From my study of Mike's capture, I would say definitely MTU
is not involved.

I am pretty sure that the problem is either:

- Some box between you and Mike that is re-writing the window scale or
related fields in the TCP header; or

- A bug in your operating system that doesn't correctly handle the
enormous window scale of 7 in Mike's request (scale 7 means multiply by
128, which could stress bad software).

Google showed me a suggestion that some intermediate boxes do their own
check of windows scaling in an attempt to protect the target system.
Apparently, some of these boxes are not able to correctly handle large
values of window scaling and they put incorrect data into fields in the TCP
header. I have saved the article somewhere to read properly in a day or
two.

I was very close to testing this setup today. I got a Windows 2000/SP4
Server, a router, and two Linux boxes connected. I used netcat to transfer
a 6K byte file from W2000 to Linux (very similar to a newsgroup download).

But I couldn't get the Linux boxes to request window scale 7. I suspect I
need to adjust the receive buffer size so the large scale makes sense, but
problems from other sources overwhelmed me...

I intend to pursue this because I am interested in low-level stuff, and I
am also trying to learn some Linux fundamentals. Probably won't be until
next week that I get another crack at a simulation.

John

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