Best utilizing fat long pipes and large file transfer

Kevin Oberman oberman at
Fri Jun 13 18:28:37 UTC 2008

> Date: Fri, 13 Jun 2008 12:40:48 -0400
> From: Robert Boyle <robert at>
> 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.

Sorry, but I don't do Windows, but my friends who do claim that this is
not true.
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751
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