[ih] when did APRANET -TIPs become known as -TACs

[Barbara Denny]

 Do you think the obsolescence of 1822 in favor of X.25 just made it easier to get rid of IMPs in the networks? 
I am thinking about the military testbed for USAREUR where I think the original deployment had CXXs (don't remember if it had C30s or C70s but leaning towards C30s).  It was deployed in that timeframe. It originally had IMPs and Cisco AGS routers  but I think SRI pulled the IMPs and just used the routers very soon after it was originally installed.
BTW, what is the story for replacing the IMP term for PSN (Packet Switching Node) and when was this done?
barbara
    On Sunday, September 28, 2025 at 10:08:29 AM PDT, Jack Haverty via Internet-history <internet-history at elists.isoc.org> wrote:  
 
 On 9/28/25 06:31, Noel Chiappa via Internet-history wrote:
>      > From: Jack Haverty
>
>      > Much of this history was probably well-documented in the reports
>      > submitted by BBN ... It may be available on discover.dtic.mil
>
> I took your suggeation, and turned up an answer to one question: there
> were C/30-based TACs, as well as one-time-TIP-based TACs.
>
>    Combined Quarterly Technical Report No. 22
>    https://apps.dtic.mil/sti/pdfs/ADA104931.pdf
>    Combined Quarterly Technical Report No. 23
>    https://apps.dtic.mil/sti/pdfs/ADA108783.pdf
>    The DDN (Defense Data Network) Course
>    https://apps.dtic.mil/sti/tr/pdf/ADA173472.pdf
>
> I found nothing about what physical interface any of them used, though,
> but I'll bet it was an 1822.
>
>     Noel

Hi Noel,

Yes, good detective work.  There's lots of information in contractor 
reports.  At every Internet Meeting there were a lot of contractors, so 
the reports from each were limited to 15 minutes or so.   Much of the 
detail wasn't even presented in the meetings, and of course not captured 
in Jon's minutes.

There's lots of technical detail in those old reports that probably 
should have been issued also as RFCs or IENs.  The reports went to 
various parts of the government, and to the people inside BBN who had 
worked on the projects, but probably not much beyond those groups.  For 
example, I assume all the other ARPA contractors had to submit similar 
reports.   But I don't recall ever seeing a report from SRI, MIT, UCLA, 
Linkabit, Collins, or any of the other contractors who attended the 
various Internet meetings.   I still haven't seen more than a handful of 
non-BBN reports, but I suspect some might be in DTIC.

At some point I was given responsibility for all of the ARPA and related 
contracts in our part of BBN.   That meant I became the "author" of the 
BBN reports.  Pragmatically what it meant was that I had to badger all 
of the project leaders to write down what their teams did during the 
quarter.   Getting blood out of a stone would have been easier than 
getting documentation out of an engineer.  For many of our contracts, 
the only required deliverables were the Quarterly Reports.   Until the 
Report was submitted, the government wouldn't pay the bill.

BTW, re C/30 et al.  Internet History has probably never been told about 
that part of the history:

The C/30 hardware was based on a BBN project called the MBB - 
Microprogrammable Building Block.  As the name implies, the hardware was 
microprogrammable.  The C/30 microcode was designed to make an MBB look 
exactly like a Honeywell 316.  So the same code that had been developed 
for the 316-based IMPs (or TIPs) would also run on a C/30.   
Effectively, a C/30 looked exactly like a Honeywell 316 to the software 
that ran on it.

Similarly, a C/70 was a Unix minicomputer also built on an MBB, but with 
an interface to disk storage and probably more RAM.  The MBB microcode 
used for a C/70 was optimized for code written in the C language, which 
was the language used by the Unix OS.

BBNCC started life as BBN Computer Corporation, with a plan to sell Unix 
boxes to the world.   Competing with DEC was probably always a bad idea, 
so later BBNCC became BBN Communications Corporation, selling IMPs to 
the marketplace as ARPANET clones, and a few C/70s operating as NOCs.   
Didn't even have to change the logo.

There was also a C/60, but I can't remember what it did.....

There's probably lots of detail in other old BBN reports, as well as 
reports from others.  For example, I just searched in DTIC for "BBN MBB" 
and found this discussion about formal verification of the C/30 
microcode: https://apps.dtic.mil/sti/tr/pdf/ADA510573.pdf   -- which 
even found bugs in the microcode.  Another timeline bit in that report - 
the 1822 interface was obsolete on DDN by 1986, in favor of X.25 for the 
Host/IMP interface.