Important New Requirement for IPv4 Requests

Kevin Oberman oberman at
Fri Apr 24 11:29:10 CDT 2009

> Date: Fri, 24 Apr 2009 19:05:26 +1200
> From: Perry Lorier <perry at>
> >
> >
> > Large data sets?  So you are saying that 512-byte packets with no 
> > windowing work better?  Bill, have you measured this?
> >
> > Time to download a 100mb file over HTTP and a 100mb interface: 20 
> > seconds.
> > Time to download a 100mb file over FTP and a 100mb interface: ~7 minutes.
> >
> > And yes, that was FreeBSD with the old version openssl library that 
> > shipped with 6.3.
> >
> As someone who copies large network trace files around a bit,  100MB at 
> 100mb, over what I presume is a local (low latency) link is barely a 
> fair test.  Many popular web servers choke on serving files >2GB or >4GB 
> in size  (Sigh).  I'm in New Zealand.  It's usually at least 150ms to 
> anywhere, often 300ms, so I feel the pain of small window sizes in 
> popular encryption programs very strongly.  Transferring data over high 
> speed research networks means receive windows of at least 2MB, usually 
> more.  When popular programs provide their own window of 64kB, things 
> get very slow.

Very few people (including some on this list) have much idea of the
difficulty in moving large volumes of data between continents,
especially between the Pacific (China, NZ, Australia, Japan, ...) and
either Europe or North America.

Getting TCP bandwidth over about 1Gbps is very difficult. Getting over
5G is nearly impossible. I can get 5Gbps pretty reliably with tuned end
systems over a 100 ms. RTT, but that drops to about 2G at 200 ms.

A good web site to read a bout getting fast bulk data transfers is:

It is aimed at DOE and DOE related researchers, but the information is
valid for anyone needing to move data on a Terabyte or greater scale
over long distances. We move a LOT of data between our facilities at
FermiLab in Chicago and Brookhaven in New York and CERN in
Europe. A Terabyte is just the opener for that data.

Also, if you see anything that needs improvement or correction, please
let me know.
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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