[zamadatix]

Things don't follow the OSI model nor have they ever really, it never caught on. The 4 layer TCP model is much more realistic (and less formalized) but even then there can be differences sometimes. You can spend a lifetime learning OSI to only end up finding a few real world protocols like IS-IS in use and co-opted to be used outside a full OSI stack anyways.

Regardless knowing the layering model to the letter tells you very little about how TCP works for instance. After all that's the reason for layers, you don't need to know how the protocol does it's thing just where it fits in the stack and what happens between the boundaries (which in the TCP model is "not much"). The other commenters suggestion of Stevens book has been the traditional recommendation though I will say it hasn't sat idle since then and you !ay want to follow it up with some more recent resources to get a complete picture of modern TCP extras.

For the UDP one also look into the design of QUIC for ideas in that space.