[ih] Arpanet line speed

[Alex McKenzie]

The initial ARPANET line from the US to the UK went via Norway and operated at 19.2kbps.  ARPA's seismic monitoring office had a 19.2kbps leased line from Washington DC to Norway for the transfer of seismic data from the NORSAR seismic array to a data processing center in DC.  This was part of the nuclear testing monitoring system used to detect Soviet underground nuclear tests.  Larry Roberts persuaded the seismic monitoring office to send the data via the ARPANET and allow the existing leased line to be incorporated into the ARPANET.  The line from NORSAR to University College London ran at the same data rate so that when no seismic data was on the transatlantic circuit the London TIP could make use of the full bandwidth.I think the British paid for the link from UCL to NORSAR, so Larry expanded ARPANET to Europe without using any money from his budget for communication links.
All of this is from memory, so the usual disclaimers about aging memories apply.
Cheers,Alex


      From: Craig Partridge <craig at tereschau.net>
 To: Andrew G. Malis <agmalis at gmail.com> 
Cc: "internet-history at postel.org" <internet-history at postel.org>; Noel Chiappa <jnc at mercury.lcs.mit.edu>
 Sent: Wednesday, January 18, 2017 10:21 AM
 Subject: Re: [ih] Arpanet line speed
   
Andy's recollection that stuff was 56 Kbps later on matches my recollection when I came on board in '83.
One thing is I don't remember what the bandwidth was on the satellite links to England.  My recollection is it washigher than 9.6Kbps but there was some oddity in integrating European and US telecom standards such that the bandwidth was different.  But this could be entirely wrong -- alas the ARPANET maps don't tell me the data rates.
Thanks!

Craig
On Wed, Jan 18, 2017 at 9:59 AM, Andrew G. Malis <agmalis at gmail.com> wrote:

By the time I came on board in '79, almost all of the links were 56 Kbps, with a few 9.6 Kbps links here and there. The 50 Kbps links had been replaced by that point.
Cheers,Andy

On Wed, Jan 18, 2017 at 9:29 AM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:

    > From: Paul Ruizendaal

    > - if the modem from the IMP to the Bell System was analog, the best
    > technology of the time was perhaps 2.4kb/s ... a speed of 50kb/s is not
    > a multiple of 2.4kb/s, and it would have required 21 parallel lines

If you read the 303 manual, it's clear that i) the signal between a pair of
303 modems was analog, not digital, and ii) there was a single line, with a
wide enough bandpass to carry signals of high enough frequency to carry that
bit rate - it didn't glue together a bunch of slower lines.

    > if the modem from the IMP to the Bell System was digital, it would most
    > likely have used a single channel of a T1 connection

The whole T hierarchy was just getting started then (initial deployment in the
early 1960s), and I'm not sure if it was deployed widely enough to have made
it possible to lease a T1 line from one coast to another.

Also, many of these lines would have crossed non-AT+T local phone companies
(the Bell System did not control all of the US phone system, although some
people don't realize that). The "History of the ARPANET: The First Decade"
(which I have previously pointed you at on another list), pg. III-32, says
"In the case of a circuit from UCLA to RAND ... the service would be procured
from General Telephone" - GT was the largest independent telephone company in
the US at that point. It's not clear that those local carriers would have
supported T1.


Moral of the story: when doing history, it's bad to make assumptions about
what was and wasn't possible, and about what did and did not happen. Find
contemporary documentation.

        Noel
_______
internet-history mailing list
internet-history at postel.org
http://mailman.postel.org/mail man/listinfo/internet-history
Contact list-owner at postel.org for assistance.



_______
internet-history mailing list
internet-history at postel.org
http://mailman.postel.org/ mailman/listinfo/internet- history
Contact list-owner at postel.org for assistance.





-- 
*****
Craig Partridge's email account for professional society activities and mailing lists.For Raytheon business, please email: craig.partridge at raytheon.com
_______
internet-history mailing list
internet-history at postel.org
http://mailman.postel.org/mailman/listinfo/internet-history
Contact list-owner at postel.org for assistance.


   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://elists.isoc.org/pipermail/internet-history/attachments/20170118/31159766/attachment.htm>