[ih] Arpanet line speed

[Vint Cerf]

1. the internal satellite link that connected the US to Norway was a shared
9.6 kib/s link. ARPANET and the NORSAR/SEISMO systems shared that channel.
I don't think that ever got higher until it was retired and replaced in
1982 when Europe was forced to go over TCP/IP on the shared SATNET 64 kb/s
link (later expanded to 128kb/s). The rest of the ARPANET hosts ran a mix
of NCP and TCP until January 1, 1983 when almost all hosts switched to
TCP/IP. There were a couple of exceptions that were given a few months'
reprieve.

2. The ARPANET leased lines were 50 kb/s until they were replaced by 64
kb/s DS0's except that 1 bit of 8 was taken as a framing bit, which stole 8
kb/s from 64 leaving 56 kb/s for data carrying in the US.

at least that is what I seem to remember.

v


On Wed, Jan 18, 2017 at 2:46 PM, Brian E Carpenter <
brian.e.carpenter at gmail.com> wrote:

> On 19/01/2017 04:21, Craig Partridge wrote:
> > 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 was
> > higher 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.
>
> Google for Peter Kirstein's paper "Early Experiences with the ARPANET and
> INTERNET in the UK"
>
> It was 9.6 between London and Norway and then 9.6 between Norway and the
> USA.
>
> 9.6 was the lowest common denominator; the US 56k standard was different
> from
> the CCITT 64k standard used in Europe. Just as the US T1 1.5M standard was
> different
> from the CCITT E1 2M standard some years later. This was a pain in the
> neck for
> early transatlantic links above 9.6 (or posibly 19.2). But I suspect that
> in 1973
> the main issue was cost.
>
>    Brian
>
> >
> > 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
> >>> _______
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> >>>
> >>
> >>
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> >>
> >
> >
> >
> >
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