> At the start, TCP handled both datagram transmission and routing, but as the protocol expanded, other researchers started to recommend that these two functions be split into layers.

> One of these researchers, Jonathan Postel of the University of California’s Information Sciences Institute and an editor for the Request of[sic] Comments (RFCs) which is a document series capturing the development of the Internet.

> Postel has stated:

> “We are screwing up in our design of Internet protocols by violating the principle of layering”

> Basically, the monolithic design of TCP would soon become inflexible and unable to scale efficiently. Therefore TCP was split into two protocols, TCP & the Internet Protocol (IP).

https://www.colocationamerica.com/blog/history-of-ip-address...