[ih] Nit-picking an origin story

[John Day]

Yea, I had always assumed that they were DS0s of a T1 until I learned that T1 didn’t exist yet, or at least was being deployed yet.  Both Baran and Davies concluded independently that 1.5Mbps would be the right data rate.

John

> On Aug 24, 2025, at 20:28, Guy Almes via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> Barbara et al.,
>  There are (at least) two issues.
> <> When the original ARPAnet IMPs were deployed, the availability of those special 50 Kb/s circuits, complete with 303A modem etc., were the key enabling technology.  As many have pointed out, something like the ARPAnet could have been built with lower-speed circuits, but it would have been much less successful both as infrastructure and as demonstration of how the future could unfold.
> 
> <> When the last additions to the ARPAnet were deployed during the 1980s, I suspect that digital 56 kb/s circuits were used.  Once the Bell system started to deploy those digital circuits, they were surely/probably both cheaper and more reliable.  Can someone verify (or falsify) that?
> 	-- Guy
> 
> On 8/24/25 12:43 PM, Barbara Denny via Internet-history wrote:
>>  You might hear 56 kb/sec from other people.  I was surprised to hear 50 kb/sec from this list somewhat recently.  Of course my memory could be wrong but i always thought it was 56 kb/sec.  Did anything change by the mid 80s? Your quotation says normally 50 kb/sec from the ARPAnet brochure in 1980.
>> barbara
>>     On Sunday, August 24, 2025 at 05:25:04 AM PDT, Lars Brinkhoff via Internet-history <internet-history at elists.isoc.org> wrote:
>>    Jack Haverty wrote:
>>> Performance was also an issue as the ARPANET grew and traffic
>>> increased.  One of the limiting factors to performance was the routing
>>> algorithm.   Packets were always sent on the "shortest" path.   But
>>> that meant that the aggregate performance was also limited to
>>> 56kb/sec, which was the maximum line speed of any path.
>> I beleve the correct number is 50,000 bits/second.
>> ARPANET Information Brochure, from 1980.
>> "The complete network is formed by interconnecting the nodes through
>> wideband communication lines, normally 50,000 bits per second (50KBPS),
>> supplied by common carriers."
>> https://urldefense.com/v3/__https://apps.dtic.mil/sti/pdfs/ ADA096798.pdf*page=19__;Iw!!KwNVnqRv! D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE- yM8vZnOWRpX72kK_NSeQtg$ <https://urldefense.com/v3/__https://apps.dtic.mil/sti/pdfs/ADA096798.pdf*page=19__;Iw!!KwNVnqRv!D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE-yM8vZnOWRpX72kK_NSeQtg$>
>> BBN Report 1928, from 1970.
>> "In the last quarter, we designed and implemented a test program to
>> obtain data on the performance of the fifty kilobit communication
>> circuits" kb/sec
>> https://urldefense.com/v3/__http://b**Arwolff.de/bbn-arpanet-reports- collection/ BBN*20(1970)*20Interface*20Message*20Processors*20for*20the*20ARPA*20Computer*20Network*20(Report*201928,*20Quarterly*20Technical*20Report*204).pdf*page=10__;w6QlJSUlJSUlJSUlJSUlJSUj!!KwNVnqRv!D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE-yM8vZnOWRpX72kJ9un2NJg$ <https://urldefense.com/v3/__http://b**Arwolff.de/bbn-arpanet-reports-collection/BBN*20(1970)*20Interface*20Message*20Processors*20for*20the*20ARPA*20Computer*20Network*20(Report*201928,*20Quarterly*20Technical*20Report*204).pdf*page=10__;w6QlJSUlJSUlJSUlJSUlJSUj!!KwNVnqRv!D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE-yM8vZnOWRpX72kJ9un2NJg$>
>> This was due to the Bell/Western Electric 303C wideband modem using a
>> group service of 12 voice circuits.
>> https://urldefense.com/v3/__https://bitsavers.org/communications/ westernElectric/ modems/303_Wideband_Data_Stations_Technical_Reference_Aug66.pdf*page=6__;Iw!!KwNVnqRv!D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE-yM8vZnOWRpX72kKcZ8ttpw$ <https://urldefense.com/v3/__https://bitsavers.org/communications/westernElectric/modems/303_Wideband_Data_Stations_Technical_Reference_Aug66.pdf*page=6__;Iw!!KwNVnqRv!D2hHWHot7vQUTsuR1iUtBsCPl1_OXbFE00gO-0aiv8dlpDRPu_x1_qu3HN6-RwfYOUiaooE-yM8vZnOWRpX72kKcZ8ttpw$>
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