[ih] Question re rate of growth of the Arpanet

Tue Apr 22 14:06:00 PDT 2025

Guy,

See brief comments inline below.

Steve

On Tue, Apr 22, 2025 at 4:44 PM Guy Almes <galmes at tamu.edu> wrote:

> Steve, Geoff, et al.,
>    I actually find this a very interesting thread and a significant gap
> in (at least) my understanding of how the ARPAnet came to be.
>
>    Although I was an ARPAnet user (as a CMU CS grad student), I only
> became aware of how long-distance digital circuits were provided when
> active in the NSFnet regional networks beginning about 1986.  At that
> time, the key technical, regulatory, and business enablers of the needed
> digital services were:
> <> technical: the Bell System's DS0, T1, and eventually T3 services.
> The fact that these T1-based services were (more or less) mature by the
> early 1980s was key for us.
> <> regulatory: the breakup of the Bell System about 1984 resulted in
> several competing long-distance carriers, each supporting the T1-based
> services and interoperating with the sort-of-regulated monopoly LECs.
> <> business: though there's more to it, the essence is the demand for
> more long-distance telephony capacity.  Many of us remember how
> expensive long-distance was and the famous busy signals on Mother's Day.
>    This story is pretty well known in our community.
>    But we often forget how fortuitous it was that these two
> "prerequisites" were in place by the mid-80s.
>
>    But this thread makes me aware that the corresponding "prerequisites"
> for the ARPAnet are less well understood.
>    What I've found so far is this:
> <> technical: Western Electric had, by 1966, developed its 303 Type
> Wideband Data Station.  This technology used a "group" of 12 voice
> channels to provide a 50 kb/s service.  (It could also use a
> "supergroup" of 60 voice channels to provide 250 kb/s or a "half-group"
> of 6 voice channels to provide 19.2 kb/s service.)
> <> regulatory: Bell System monopoly, but with the government,
> particularly during the Cold War era, as an important special customer.
> <> business: here's where I'm weakest.  More in the next paragraph.  Why
> did the Bell System find it "good business" to develop these wideband
> services?
>    It occurred to me that I've "always known" that the ARPAnet used
> 50-kb/s leased lines based on some kind of "modem".
>    If, somehow, those Bell System 50-kb/s digital services had not been
> available, then would the ARPAnet been successful?
>

Interesting question, but I don't know enough to even speculate.  Larry
Roberts explored various options and was committed to building the Arpanet
before he became aware of the government rate for 50 kb/s lines, so I
imagine the Arpanet would have been build even if the 50 kb/s service was
not available.  But would it have been successful?  Too hard to tell.

>
>    So here are my hunches on the "business" part of the story:
> <> I don't think it was used in the SAGE system.  What I've seen so far
> about the technology of SAGE (which was deployed beginning 1959), it
> used 1200-b/s modems.
> <> I don't think it was used much by the TV industry.  This had been my
> hunch, and I allow that I might be wrong about this, but my impression
> is that the TV industry had their own technologies for using
> long-distance cables and microwaves.
> <> I think it might well have been used for NASA telemetry etc., but I
> don't have any specific evidence.
> <> I think it was used by the SABRE airline reservation system.
>

On reading the description of the 303 series modems, it seems clear to me
there was substantial use of wideband communication.  By whom and for what
I don't know.

>
>    But this is pretty sketchy.
>    I'd welcome input from others.
>    My key objective is to better understand why the long-distance
> telecommunications industry (in this case, the Bell System) had created
> this premium wideband digital service in the pre-T1 era such that, when
> the ARPAnet designers were doing their work, 50-kb/s long-distance
> service was available.
>
>    Thanks in advance to any additions or corrections,
>         -- Guy
>
> On 4/21/25 2:08 PM, the keyboard of geoff goodfellow via
> Internet-history wrote:
> > steve, can you elucidate any history with respect to how/why the speed of
> > 50 kb/s was chosen for the ARPANET lines?  were there great speeds
> > available then?
> >
> > yours truly kinda (perhaps mistakenly) recalls these 50 kb/s "wideband
> > circuits of the day" were primarily used for linking tv broadcast
> affiliate
> > stations to/with their motherships (cbs, nbc, abc, ...)?
> >
> > geoff
> >
> > On Mon, Apr 21, 2025 at 7:26 AM Steve Crocker via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> >
> >> Thanks for the pointer to RFC 597.
> >>
> >> As I looked at it, an aspect I hadn't considered before came to mind.
> >>
> >> Installation of an IMP required provisioning 50 kb/s lines to two or
> three
> >> other points.  In the early days, we installed roughly a new IMP once a
> >> month.  (The lead time for ordering 50 kb/s lines from AT&T was NINE
> >> months.)
> >>
> >> Once an IMP was installed, new hosts could be added to the IMP as
> quickly
> >> as the site could build or obtain the host-IMP interface and write or
> >> obtain the software for their operating system.
> >>
> >> If anyone has the dates for each of the hosts, it would be interesting
> to
> >> compare the growth of IMPs vs growth of hosts.
> >>
> >> Steve
> >> --
> >> Internet-history mailing list
> >> Internet-history at elists.isoc.org
> >> https://urldefense.com/v3/__https://elists.isoc.org/mailman/listinfo/
> > internet-history__;!!KwNVnqRv!
> >
> CvnEaxskHMjf5GDDAK0yK26KGlSUJU3NOkWGxNhpUZy2w019Knw4jAy7yaqEPt6QipJlK7Z2kh6L19IKzgKMXGaLQDRZkw$
> <
> https://urldefense.com/v3/__https://elists.isoc.org/mailman/listinfo/internet-history__;!!KwNVnqRv!CvnEaxskHMjf5GDDAK0yK26KGlSUJU3NOkWGxNhpUZy2w019Knw4jAy7yaqEPt6QipJlK7Z2kh6L19IKzgKMXGaLQDRZkw$
> >
> >>
> >>
> >
> > --
> > Geoff.Goodfellow at iconia.com
> > living as The Truth is True
> > --
> > Internet-history mailing list
> > Internet-history at elists.isoc.org
> > https://urldefense.com/v3/__https://elists.isoc.org/mailman/listinfo/
> > internet-history__;!!KwNVnqRv!
> >
> CvnEaxskHMjf5GDDAK0yK26KGlSUJU3NOkWGxNhpUZy2w019Knw4jAy7yaqEPt6QipJlK7Z2kh6L19IKzgKMXGaLQDRZkw$
> <
> https://urldefense.com/v3/__https://elists.isoc.org/mailman/listinfo/internet-history__;!!KwNVnqRv!CvnEaxskHMjf5GDDAK0yK26KGlSUJU3NOkWGxNhpUZy2w019Knw4jAy7yaqEPt6QipJlK7Z2kh6L19IKzgKMXGaLQDRZkw$
> >
> >
>
>

-- 
Sent by a Verified

sender