From: John Beckett 

"Geo"  wrote in message
news::
> thanks, that's the one I needed.

 BTW I was recently reading about QoS stuff. Apparently it is quite
possible for a quality-of-service router connecting you to the Internet to
*change*  window scaling options in the packets that it is forwarding.

The concept is that the host that advertises a large receive window
probably does not realise that it is connecting to a WAN with a lower
connection speed than the local network. The large receive window could
cause routers on the edge of the WAN to tie up large buffers while waiting
for the lower-speed WAN to forward the traffic.

So, the friendly QoS router might change the TCP options advertised when
the connection is opened (to something that the router believes is more
appropriate for WAN traffic).

Anyway, that sort of behaviour could explain what Mike observed in his
capture. Mike's Linux computer advertised a large receive window, but Geo's
W2000 computer didn't seem to understand what was going on. Maybe an
intermediate QoS device had kindly altered the options, presumably in a
rather broken (or incomplete) fashion.

John

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