For historical amusement...
In reading the Phase II NSP spec, I spotted a summary of how that differs from Phase I.
I've never seen any Phase I documents (perhaps no formal documents ever existed?).
From the discussion in the Phase II spec, it's clear that Phase I is quite a different
protocol. Phase II through IV are all very closely related, especially at layer 4 and
above. Not so Phase I -- it would be quite difficult (at best) to make an NSP
implementation that could speak both Phase I and Phase II. I don't see any signs
that this was ever done. For example, there is no "how to interoperate with the
previous version" chapter in the Phase II spec -- unlike the Phase III and IV specs.
paul