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[ih] NCP and TCP implementations

Hi, all, I've been meaning to respond to this thread, but I wanted to look at
some old host tables first, since as an amateur historian I'm only too aware
of how fallible human memory is (see here:

for an amusimg story about that), _but_ I couldn't find any online!

I did have a modest collection of them at home, but didn't have access to them
where I was. I have now put them all online here:


and will add a link to them from my "ARPANET Technical Information" page:


when I get a chance. They are a mixture of NIC- and MIT-format host tables. If
anyone has any that are missing from that set that they'd like me to add,
please contact me off-list.

Anyway, on to what I wanted to comment on:

    > From: Geoff Goodfellow

    > for some reason when the C/70's came along, TIP's were renamed to TAC's

IIRC, the C/70's were timesharing machines (running Unix, IITC); the C/
machines which were packet switches (IMPs), terminal concentators (TACs) etc
were C/30's. I note from the host tables that the TIP's all seem to have been
H316's, and all TAC's were C/30's.

I don't recall there difference between a TIP and a TAC, but in addition to
the hardware, the TAC may have been (as someone suggested) a TCP machine. Someone
needs to check this, though, as the February 1983 host table (above) shows a
few TIP's (on H316's), which was after the NCP->TCP conversion (January '83).

My memories of what happened at MIT are confused, since it's all mixed up with
the addition of a 3rd IMP to MIT (IMP 77), which IIRC was one of the first
C/30 IMPs. Actually, I'm pretty sure that there were two new C/30 IMPs at that
point, one of which replaced IMP 44, (a TIP, which IIRC was turned into a host),
and I do see this line:

  ;;; 254,MIT-TIP,TIP,USER,NEW has moved to 2/77.

in the Aug/82 host table. (By the January/83 table, it had turned into a C/30,
and was MIT-TAC. So it must have quickly been converted from an H316 to a
C/30, but I have no memory of that.)

    > let's also not forget that the MIT ITS (Incompatible Timesharing System)
    > hosts MIT-AI, MIT-ML and MIT-DM did not have passwords

Initially, no; later, under pressure from DARPA, passwords were added (along
with a liberal policy on guest accounts).