[ih] Question re rate of growth of the Arpanet

Mon Apr 21 11:53:39 PDT 2025

Hi all,

In the paper “Analytic and simulation methods in computer network design” <https://dl.acm.org/doi/pdf/10.1145/1476936.1477022>, I show the tariffs available back then.  Specifically, in Table 1, I show the "Publicly Available Leased Transmission Line Costs” and, more importantly, in Table 2, I show the "Estimated Leased Transmission Line Costs Based on Telpak Rates.” and it is the Telpak lines that Larry used to provision the Arpanet.  Note that there is a specific 50Kbps offering in the Telpak offering. Note also that at 50Kbps, the Telpak tariff is considerably more economical than the public tariff.

Len

> On Apr 21, 2025, at 2:40 PM, Steve Crocker via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> I may be wrong about 9.6.  It's what I recall when this was relayed to me,
> but I'd want to track down a more authoritative source.
> 
> Re U.S. distances: In 1968 I was in Boston until May and then in Los
> Angeles.  The University of Utah was just barely beginning to come to
> people's attention in the computer science community.  When I mentioned the
> university to people in Boston, someone said it was near Los Angeles.  When
> I mentioned it to a friend in Los Angeles, she thought it was near Chicago
> :)
> 
> Steve
> 
> 
> On Mon, Apr 21, 2025 at 2:33 PM John Day <jeanjour at comcast.net <mailto:jeanjour at comcast.net>> wrote:
> 
>> theRoberts had originally planned to use 2.4Kbps lines. Roger Scantlebury
>> (and others) at the Gatlinburg Operating System Conference in the Fall of
>> 67 (it appears to have been one of *those* bar discussions) ;-) convinced
>> him that given NPL’s experience with their packet-switched network they had
>> found that that was way too slow and he should use 50Kbps.
>> 
>> Both Baran and Davies independently had come to the conclusion that
>> 1.5Mbps would be best but it wasn’t available yet.
>> 
>> There are two things I find amusing about this:
>> 1) The ARPANET would have worked at 2.4 or 9.6, etc. But would have been
>> deemed so slow to prove that the effort wasn’t really successful. At 50K,
>> we could really get work done. Not many systems could sustain that and
>> there weren’t many applications needing all of that. Using 50K was a much
>> larger part of the ARPANET’s success than we often give it credit for.
>> 
>> 2) Roger’s experience was for the NPL campus network. I am not sure Roger
>> had any idea what 50K (which were expensive!) would do to Roberts budget
>> for a nation-wide network in the US.  ;-) At the time, most Europeans and
>> many East Coast Americans had no sense of distances in the US. (I remember
>> a tale of 3 IBMers sent from Poughkeepsie to Detroit to work on some
>> customer's system, who thought as long as they were that far West, they
>> could drive to Las Vegas for the weekend.) (!!) ;-) (31 hours now with
>> Interstates which were not complete then.)  Good thing ARPA’s pockets were
>> deep. ;-)
>> 
>> O, and at that conference, Roger convinced Roberts to use packet
>> switching, which he had not heard of. (He did find Baran’s papers in a
>> stack he hadn’t read when he got back to DC.)
>> 
>> Both are great serendipity, that had a profound effect and for the most
>> part lost in history. I always find these kinds of things delightful.
>> 
>> Take care,
>> John
>> 
>>> On Apr 21, 2025, at 14:08, the keyboard of geoff goodfellow via
>> Internet-history <internet-history at elists.isoc.org> 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
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>>>> Internet-history at elists.isoc.org
>>>> https://elists.isoc.org/mailman/listinfo/internet-history
>>>> 
>>>> 
>>> 
>>> --
>>> Geoff.Goodfellow at iconia.com
>>> living as The Truth is True
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>> 
>> 
> 
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