North American Network Operators Group
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Re: Best utilizing fat long pipes and large file transfer

  • From: Deepak Jain
  • Date: Fri Jun 13 13:38:11 2008


Robert Boyle wrote:
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.



I'll stipulate that I haven't looked too deeply into this problem for Windows systems.

But I can't imagine it would be too hard to put a firewall/proxy (think Socks) and set the FW/proxy to adjust (or use an always on, tuned, tunnel) the TCP settings between the two FW/proxies on either side of the link.

It has reasonably little invasion or reconfiguration and is probably reasonably solid.

DJ