Best utilizing fat long pipes and large file transfer

Robert Boyle robert at
Thu Jun 12 23:26:56 UTC 2008

At 06:37 PM 6/12/2008, you wrote:
>I'm looking for input on the best practices for sending large files 
>over a long fat pipe between facilities (gigabit private circuit, ~20ms RTT).
>I'd like to avoid modifying TCP windows and options on end hosts 
>where possible (I have a lot of them). I've seen products that work 
>as "transfer stations" using "reliable UDP" to get around the 
>windowing problem.
>I'm thinking of setting up servers with optimized TCP settings to 
>push big files around data centers but I'm curious to know how 
>others deal with LFN+large transfers.

In our experience, you can't get to line speed with over 20-30ms of 
latency using TCP regardless of how much you tweak it. We transfer 
files across the US with 60-70ms at line speeds with UDP based file 
transfer programs. There are a number of open source projects out 
there designed for this purpose.


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