I can answer some of the below, as I was looking into that a few years ago.
81. Q: What was the first Unix network?
A: spider
You thought it was Datakit, didn't you? But Sandy Fraser had an earlier
project.
When did Alexander G Fraser's spider cell network happen? For that matter,
when did Datakit happen? I can't find references to either start date on
line (nor anything on spider except for references to it in Dr Fraser's
bio). I can find references to Datakit in 1978 or so.
Spider was designed between 1969 and 1974 - the final lab report (#23) dates from December
1974. It was based around a serial loop running at T1 signalling speed (~1.5Mhz). Here is
a video recorded by Dr. Fraser about it:
https://www.youtube.com/watch?v=ojRtJ1U6Qzw
(first half is about Spider, second half about Datakit).
It connected to its hosts via a (discrete TTL-based) microcontroller or “TIU” and seems to
have been connected almost immediately to Unix systems: the oldest driver I have been able
to locate is in the V4 tree
(
https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/dmr/tdir/tiu.c) It used a
DMA-based parallel interface into the PDP11. As such, it seems to have been much faster
than the typical Datakit connection later - but I know too little about Datakit to be
sure.
There is an interesting visit report from 1975 that discusses some of the stuff that was
done with Spider here:
https://stacks.stanford.edu/file/druid:rq704hx4375/rq704hx4375.pdf
Beyond those experiments I think Spider usage was limited to file serving (’nfs’ and
‘ufs’) and printing (’npr’). It would seem logical that it was used for remote login, but
I have not found any traces of such usage. Same for email usage.
From what little I know, I think that Datakit became operational in a test network in 1979
and as a product in 1982.
I thought the answer was "ARPANET" since we
had a NCP on 4th edition Unix
in late 1974 or early 1975 from the University of Illinois dating from that
time (the code in TUHS appears to be based on V6 + a number of patches).
“Network Unix” (
https://www.rfc-editor.org/rfc/rfc681.html) was written by Steve Holmgren,
Gary Grossman and Steve Bunch in the last 3 months of 1974. To my best knowledge they used
V5 and migrated to V6 as it came along. I think they were getting regular update tapes,
and they implemented their system as a device driver (plus userland support) to be able to
keep up with the steady flow of updates. Greg Chesson was also involved with this Arpanet
Unix.
As far as I can tell, Arpanet Unix saw fairly wide deployment within the Arpanet research
community, also as a front end processor for other systems.
A few years back I asked on this list why “Network Unix” was not more enthusiastically
received by the core Unix development team and (conceptually) integrated into the main
code base. I understood the replies as that (i) people were very satisfied with Spider;
and (ii) being part of Bell they wanted a networking system that was more compatible with
the Bell network, i.e. Datakit.
==
In my opinion both “Spider Unix” and “Arpanet Unix” threw a very long conceptual shadow.
From Spider onwards, the Research systems viewed the network as a device (Spider), that
could be multiplexed (V8 streams) or even mounted (Plan9). The Arpa lineage saw the
network as a long distance bidirectional pipe, with the actual I/O device hidden from
view; this view persists all the way to 4.2BSD and beyond.
I often wonder if it was (is?) possible to come up with a design with the conceptual
clarity of Plan9, but organised around the “network as a pipe” view instead.