923 Mbps across the Ocean ...

Sat Mar 8 21:26:38 UTC 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 <awhitney at haystack.mit.edu>
Hans Hinteregger <hhinteregger at haystack.mit.edu>
Hisao Uose <uose.hisao at lab.ntt.co.jp>
Craig Walker < cwalker at nrao.edu>

> 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: alex at yuriev.com [mailto:alex at yuriev.com]
> Sent: Saturday, March 08, 2003 12:23 PM
> To: Jason Slagle
> Cc: Richard A Steenbergen; fingers; nanog at merit.edu
> 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

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