[ih] Arpanet line speed

[jnc at mercury.lcs.mit.edu (Noel Chiappa)]

    > 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