[ih] IMP PSN 7 (was: History from 1960s to 2025 (ARPANET to TCP))

[Andrew G. Malis]

Jack Haverty wrote:

I was at BBN from 1977 to 1990 in the same group that had built the
ARPANET.   During that time, the internal mechanisms of the IMP "subnet"
changed significantly.   I remember the introduction of "PSN7" and the
lengthy and elaborate process (analysis, simulations, tests, etc.) to
assure that the transition went well (it did, PSN6 was replaced by
PSN7).  More info on the process is in DTIC.   One such report is
https://apps.dtic.mil/sti/pdfs/ADA121350.pdf


Jack, the report that you cite is for earlier IMP routing improvements that
preceded PSN 7. I was the project leader for PSN 7, which focused on a
complete rewrite of the end-to-end protocols in the IMPs (then called
PSNs). PSN 7 work was done in the mid-80s, and is best documented in RFC
979 (https://datatracker.ietf.org/doc/html/rfc979). Your recollection is
correct regarding the extensive work we did to make sure that the
transition from PSN 6 to PSN 7 was smooth.

Cheers,
Andy