Date: Thu, 12 Jun 2008 15:37:47 -0700 From: Sean Knox <sean@craigslist.org>
Hi,
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.
Not very fat or very long. I need to deal with 10GE over 200 ms (or more). These should be pretty easy, but as you realize, you will need large enough windows to keep the traffic in transit from filling the window and stalling the flow. The laws of physics (speed of light) are not forgiving. There is a project from Martin Swaney at U-Delaware (with Guy Almes and Aaron Brown) to do exactly what you are looking for. http://portal.acm.org/citation.cfm?id=1188455.1188714&coll=GUIDE&dl=GUIDE and http://www.internet2.edu/pubs/phoebus.pdf ESnet, Internet2 and Geant demonstrated it at last November's SuperComputing Conference in Reno. The idea is to use tuned proxies that are close to the source and destination and are optimized for the delay. Local systems can move data through them without dealing with the need to tune for the delay-bandwidth product. Note that this "man in the middle" may not play well with many security controls which deliberately try to prevent it, so you still may need some adjustments. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751