Best utilizing fat long pipes and large file transfer

Robert Boyle robert at
Fri Jun 13 16:40:48 UTC 2008

At 12:01 PM 6/13/2008, Kevin Oberman wrote:
>Clearly you have failed to try very hard or to check into what others
>have done. We routinely move data at MUCH higher rates over TCP at
>latencies over 50 ms. one way (>100 ms. RTT). We find it fairly easy to
>move data at over 4 Gbps continuously.

That's impressive.

>If you can't fill a GE to 80% (800 Mbps) at 30 ms, you really are not
>tying very hard. Note: I am talking about a single TCP stream running
>for over 5 minutes at a time on tuned systems. Tuning for most modern
>network stacks is pretty trivial. Some older stacks (e.g. FreeBSD V6)
>are hopeless. I can't speak to how Windows does as I make no use of it
>for high-speed bulk transfers.

Let me refine my post then...
In our experience, you can't get to line speed with over 20-30ms of 
latency using TCP on _Windows_ regardless of how much you tweak 
it. >99% of the servers in our facilities are Windows based. I should 
have been more specific.


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