I'm traveling so can not offer a good answer at the moment. But pre-BSD networking was the the MIT-Chaosnet code which Ron is alluding. Putting devices names in the UNIX space was done. Why Joy decided to abandon it will never know without asking him. Maybe it was because RIG and Accent (Mach's predecessors) had not and Bill was definitely trying to add features that those systems had.
Anyway, when I get back I can try to answer some questions about it. I think it was recently recovered.
Side note to Dan - I just quick looked at you post -- it seems excellent, I want some time to digest.
Clem