One place you will end up sooner or later is
https://www.rfc-editor.org
Here you can find every RFC ever written beginning back in 1968 through today.
RFC1122 (October 1989) list the original TCP/IP model, and this would be a good place to start.
https://www.rfc-editor.org/search/rfc_search_detail.php will get you to the intro page
where you can download a PDF or ASCII text file for RFC1122
This document will give you a good understanding of the overall original concept. From here you can
move forward and search for changes as the protocol evolved.
Use
https://www.rfc-editor.org/rfc-index-100a.html to browse all or the RFC's and find parts you wish to know more about.
If you want even more, purchase the book Cisco CCENT/CCNA ICND1 100-101 (and perhaps even 200-201) Certification Guide.
Even if you have no intention of being certified if you read this, you can't help but learn
Tek-Tips has a TCP/IP frrum here:
https://python-forum.io/editpost.php?pid=18824
various networking tips:
https://forum.ivorde.com/tcp-ip-networking-f19.html