Slow T3

We have just put in a point to point T3. I have a Cisco 3845 with an NM1-T3 card at each end. If I open an FTP connection from one end to the other, I only get about 6Mbit of throughput. It doesn't seem to matter which combination of machines I use on either end (i.e. windows

-> linux, linux->linux, etc.) If I open a bunch of connections from several machines I can max out the connection at about 45Mbit, thereby I don't believe it is being limited by my provider.

Ping times between sites average around 16ms. I am showing no errors on any of the interfaces.

What are my next steps in troubleshooting this?

Thanks. Travis

Reply to
tghaas
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I'd use Iperf and get packet traces. If Iperf will get 45Mbps with single TCP connection you can rule out T3 and concentrate on end hosts. If not - packet traces can shed some light on why performance is poor.

Regards, Andrey.

Reply to
Andrey Tarasov

Look into / Google tcp "big windows." Some hosts can't fill up a T3 with default tcp settings.

-ja

Reply to
John Agosta

Bandwidth Delay Product

Short answer "Takes too much time to ACK data, therefore we dont 'fill up the pipe' with data in transit. By changing windowing values, you can send more un-ACKed data, therefore getting closer to the actual bandwidth with a single TCP stream."

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Try some of this guide for your OS on each end (ftp client and server) if possible and report your results.

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Reply to
cf_0x2102

Thanks for everyone's help. I now have this sorted out and am able to get about 30Mbit, I'll work some more on tweaking this to try to squeeze a bit more performance.

It was the registry settings in windows that fixed this issue.

Thanks again. Travis

Reply to
tghaas

Here's another good source of info:

Sam

Reply to
Sam Wilson

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