Windows slow on fat WAN pipes

G

Guest

Guest
Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

We have just upgraded our WAN links to 155Mbit. The links vary from 300 to
3000km in length, with latency on the shortest link of about 4ms up to about
45ms on the longest link. With a linux box at each end and suitable tuning
of the tcpip parameters we can max out a link, but the best we can manage to
get with a Win2000 server box at each end is about 20Mbit/sec between the
Windows machines. This is after setting the TCPWindowSize, TCP1323Opts, and
GlobalMaxTCPWindowSize parameters in the registry on the Win2000 boxes and
rebooting them. We've tried various combinations of parameters without
getting much improvement. eg the initial suggestion of

TCPWindowSize 131400
GlobalMaxTCPWindowSize 131400
TCP1323Opts 3

Gives us about 20Mbit, and nothing else has improved on that. Any
suggestions?

Nick Payne
 
G

Guest

Guest
Archived from groups: microsoft.public.windowsnt.protocol.tcpip (More info?)

On further testing, this seems to be a shortcoming of SMB. From looking
at the traces, it doesn't seem to use the sliding window. Using ftp
between two Windows boxes, we can get several times the throughput that
we can get with a file system copy.

Nick

Nick Payne wrote:
> We have just upgraded our WAN links to 155Mbit. The links vary from 300 to
> 3000km in length, with latency on the shortest link of about 4ms up to about
> 45ms on the longest link. With a linux box at each end and suitable tuning
> of the tcpip parameters we can max out a link, but the best we can manage to
> get with a Win2000 server box at each end is about 20Mbit/sec between the
> Windows machines. This is after setting the TCPWindowSize, TCP1323Opts, and
> GlobalMaxTCPWindowSize parameters in the registry on the Win2000 boxes and
> rebooting them. We've tried various combinations of parameters without
> getting much improvement. eg the initial suggestion of
>
> TCPWindowSize 131400
> GlobalMaxTCPWindowSize 131400
> TCP1323Opts 3
>
> Gives us about 20Mbit, and nothing else has improved on that. Any
> suggestions?