[56404] in North American Network Operators' Group
Re: 923 Mbps across the Ocean ...
daemon@ATHENA.MIT.EDU (David G. Andersen)
Fri Mar 7 16:38:27 2003
Date: Fri, 7 Mar 2003 16:37:51 -0500
From: "David G. Andersen" <dga@lcs.mit.edu>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: nanog@nanog.org
In-Reply-To: <Pine.LNX.4.44.0303072205300.3222-100000@uplift.swm.pp.se>
Errors-To: owner-nanog-outgoing@merit.edu
On Fri, Mar 07, 2003 at 10:09:51PM +0100, Mikael Abrahamsson quacked:
>
> On Fri, 7 Mar 2003, Richard A Steenbergen wrote:
>
> > Production commercial networks need not apply, 'lest someone realize that
> > they blow away these speed records on a regular basis.
>
> What kind of production environment needs a single TCP stream of data
> at 1 gigabit/s over a 150ms latency link?
>
> Just the fact that you need a ~20 megabyte TCP window size to achieve this
> (feel free to correct me if I'm wrong here) seems kind of unusal to me.
It's unusual, but it's not completely unheard of. One of the biggest
sources of such data is VLBI (interferometry to measure the movement
of the earth's crust), in which signals from geographically distributed
measurement sites have to be recorded and correlated at a central site:
http://web.haystack.edu/vlbi/vlbisystems.html
The signals are massive. Right now they use specially made tape
drives that can record 1Gb/s:
ftp://web.haystack.edu/pub/mark4/memos/230.2.pdf
ftp://web.haystack.edu/pub/mark4/memos/HDR_concept.PDF
and they send the data around via airplanes. They'd love to be
able to do real-time correlation of the data, but that
involves collecting 6 of these feeds at a central site (more coming).
The feeds must be capable of running unattended for up to 24 hours
(86 terabytes each, or an aggregate of half a petabyte per day).
Yes, backbones push more than a gigabit across links, but not as
for a single flow of data.
-Dave
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