North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: 923 Mbps across the Ocean ...

  • From: Marshall Eubanks
  • Date: Fri Mar 07 17:01:32 2003 
On Friday, March 7, 2003, at 04:37  PM, David G. Andersen wrote:


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).
VLBI is moving to hard drive replacements for the expensive 1 inch tapes currently
used (known as Mark V). There are active projects for "e-VLBI" - at CRL in Japan

http://www.ntt.co.jp/news/news01e/0107/010706.html

and at Haystack Observatory in Massachusetts

http://web.haystack.edu/e-vlbi/meeting.html

In e-VLBI there is no need for reliable transmission and UDP is the way to go.

I am still involved with this peripherally, especially with the idea that the traffic be sent
"worse than best effort", so as not to collide with regular traffic.

BTW, when I did VLBI for the Navy, we used to move literally tons of tapes around the world
per month and achieved sustained bandwidths > 1 Gbps, albeit with FED-EX, not routers.

Yes, backbones push more than a gigabit across links, but not as
for a single flow of data.

-Dave

--
work: [email protected] me: [email protected]
MIT Laboratory for Computer Science http://www.angio.net/
I do not accept unsolicited commercial email. Do not spam me.

                                 Regards
                                 Marshall Eubanks

T.M. Eubanks
Multicast Technologies, Inc.
Phone : 703-293-9601       Fax     : 703-293-9609
e-mail : [email protected]
http://www.multicasttech.com

 Our New Multicast Workshop :
 http://www.multicasttech.com/workshop