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Re: 923 Mbps across the Ocean ...

  • From: Marshall Eubanks
  • Date: Sat Mar 08 16:29:16 2003

e-VLBI could easily live with a 1% packet loss rate, so I see no need for it to use TCP. (Much higher and the correlator hardware
will probably start having trouble staying in sync.)

The 1.8 Gbps igrid2002 demo used UDP, for example.

http://www.hep.man.ac.uk/~rich/VLBI_web/igrid2002_index.html

On Saturday, March 8, 2003, at 03:43 PM, Cottrell, Les wrote:


We have been talking to the radio astronomy people. We are aware they have such needs, however, I am unclear whether they have succeeded in transmitting single stream TCP application to application throughput of 900Mbits/s over 10,000km on a regular basis. Perhaps you could point me to whom to talk to. I am aware of the work of Richard Hughes-Jones of Manchester
Alan Whitney <[email protected]>
Hans Hinteregger <[email protected]>
Hisao Uose <[email protected]>
Craig Walker < [email protected]>
University and others and the Radio Astronomy VLBI Data Transmission (see for example http://www.hep.man.ac.uk/~rich/VLBI_web/) since we have shared notes and talked together a lot on the high performance issues. My understanding is that for today they use special high performance tapes to ship the data around, and are actively looking at using the network.
Today, yes, although the disk drive based Mark 5 system will be rapidly rolled out, as it will substantially reduce operating costs.

http://web.haystack.mit.edu/e-vlbi/whitney.pdf

(BTW, the Mk5 deployment plan
http://ivscc.gsfc.nasa.gov/program/Mk5plan_disks.pdf
involves buying a metric ton of shippable disk drives.)

Tape shipping for the USNO VLBI correlator is on the order of $ 50K per month (not counting recorder maintenance), so the
real question is, when will it be possible to ship 1 Gbps data by fiber cheaper than than by FedEx. As the data are loss tolerant, and as buffers are cheap, thus the interest in using worse than best effort bandwidth. (If anyone is interested in the
this, I am trying to have an informal bar bof to discuss it at the SF IETF.)

I cannot see how this is really relevant to NANOG and would suggest that it be taken off list.

-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Saturday, March 08, 2003 12:23 PM
To: Jason Slagle
Cc: Richard A Steenbergen; fingers; [email protected]
Subject: Re: 923 Mbps across the Ocean ...




On Sat, 8 Mar 2003, Richard A Steenbergen wrote:
A) The amount of arrogance it takes to declare a land speed "record" when
there are people out there doing way more than this on a regular
basis.
Single stream at 900mbs over that distance?  Where?

Talk to folks that deal with radio telescopes.

Alex


                                 Regards
                                 Marshall Eubanks


T.M. Eubanks
Multicast Technologies, Inc.
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