[myself248]

Nothing off the top of my head that's succinct and readable.

You'd do well to paw through the Bell Systems Technical Journal -- there's some amazing stuff in there like the origins of Unix and C [1], or Shannon's information theorem [2] -- but some details of the network itself are either hard to search for, or might not be there at all.

1: https://archive.org/details/bstj57-6-1991

2: https://archive.org/details/bstj27-4-623

Most of the old phreak philes are focused on the billing and routing aspects of the network, not so much on transport. I remember a few test equipment manuals had good introductions to the structure of a T1 frame, for instance, but perhaps not an exhaustive treatment of how that came to be.

This is an interesting question. It must be out there, mustn't it?