[ih] ARPANet anniversary

[Bernie Cosell]

On 2 Nov 2009 at 10:43, Noel Chiappa wrote:

> Something I'm curious about, though: how much of this stuff was all
> demonstrated internally at BBN, first? E.g. I would have guessed that the
> first frame (for want of a better word to differentiate IMP-IMP datagrams
> from host-host datagrams) sent from one IMP to another happened at BBN?

Yes.  We had a three-node network up and fully running [we could debug 
the routing code and such with it].

> Did BBN have any host-IMP host interfaces (and hosts) they could play with,
> or were the host interfaces at the user sites the first ones actually plugged
> in and tried?

Those were the first *hardware* host interfaces.  I can't remember when 
we connected up an actual host to an IMP at BBN -- the host interface 
hardware must have been shaken down by Severo's crew but I can't remember 
anything about how that happened.  The host *code* in the IMP was already 
pretty much debugged: the way we implemented the imp-TTY to imp-TTY 
communication (which had been up and working solidy quite a while before 
the IMP was even shipped west) was by a "fake host".  What the TTY 
handler did, for both send and receive, was simulate acting as a real 
host [and so all the reassembly, RFNMs, etc, stuff was exercised by it].  
There was another fake host that was a little DDT-like debugger that also 
ran as a host and hacking from the IMP console TTY was a little like 
using telnet [a decade later..:o)]: you had to tell the local TTY handler 
"connect me to Host X at IMP Y" and then it just acted as a regular host, 
sending and receiving traffic.  If the "remote host" was the other IMP's 
TTY, then we had a primitive IM system; if the "remote host" was the 
other IMP's debugger, we could restart the IMP, install patches, etc.  We 
could [did] help debug actual host code that way [sending to/from a 
"real" host from our TTY "fake" one].

And so, also as a systems guy, that's why I was relatively unimpressed 
with the host->host "L O <crash>": the *system* had _already_ been pretty 
much tested.  The 1822 host interface was just one of a number of "host 
plugins" that the IMP code handled [including the TIP, which also ran as 
a "fake host"].  From *my* point of view, the only real new ground that 
was broken there [and that was done well before the "L O"] was that the 
Imp-Imp modem code was actually running over a relatively-long real-world 
communications line [with real delays, errors, noise, etc] rather than on 
our testbed].

  /Bernie\
-- 
Bernie Cosell                     Fantasy Farm Fibers
mailto:bernie at fantasyfarm.com     Pearisburg, VA
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