Slight tangent that actually shocked me when I learned about it: the OSI model that everyone keeps talking about is actually not the "official" nor "real" implementation we use. The actual protocol (and conceptual model) you really want to learn and work with is simply called "Internet Protocol Suite", commonly known as "TCP/IP".

Consider this comparison between OSI and TCP/IP models from Wikipedia[1]:

> The OSI protocol suite that was specified as part of the OSI project was considered by many as too complicated and inefficient, and to a large extent unimplementable. Taking the "forklift upgrade" approach to networking, it specified eliminating all existing networking protocols and replacing them at all layers of the stack. This made implementation difficult, and was resisted by many vendors and users with significant investments in other network technologies. In addition, the protocols included so many optional features that many vendors' implementations were not interoperable.

> Although the OSI model is often still referenced, the Internet protocol suite has become the standard for networking. TCP/IP's pragmatic approach to computer networking and to independent implementations of simplified protocols made it a practical methodology. Some protocols and specifications in the OSI stack remain in use, one example being IS-IS, which was specified for OSI as ISO/IEC 10589:2002 and adapted for Internet use with TCP/IP as RFC 1142

There's a similar discussion on the TCP/IP article as well[2], highlighting the impracticality of OSI "layers" in terms of implementation.

> The IETF protocol development effort is not concerned with strict layering. Some of its protocols may not fit cleanly into the OSI model, although RFCs sometimes refer to it and often use the old OSI layer numbers. The IETF has repeatedly stated[citation needed] that Internet protocol and architecture development is not intended to be OSI-compliant. RFC 3439, addressing Internet architecture, contains a section entitled: "Layering Considered Harmful".

In practice, a short discussion about SSL/TLS is enough to point the inadequacies of OSI, and orient one towards conforming their conceptual model closer to TCP/IP and relevant RFC's.

The advice I follow personally, given the "popularity" of OSI (people call "layer 1-7" as if it were an actual thing, 90% of the blogs and literature uses the OSI model), is to simply translate into TCP/IP lingo/concepts in your mind whenever you read/speak about it. Not everyone will get it around you, but at least you'll have a more solid implementation should you be working with low-levels of the net stack.

For reference, RFC 1122[3] defines the Internet Protocol Suite with 4 layers: application, transport, internet (or internetwork, the idea of routing) and link. Does not assume or require a physical layer in the spec itself — hence it works on 'anything' from USB to Fiber passing by Ethernet or Bluetooth and PCIe/Thunderbolt if you just follow the protocol.

[1]: https://en.wikipedia.org/wiki/OSI_model#Comparison_with_TCP/...

[2]: https://en.wikipedia.org/wiki/Internet_protocol_suite#Compar...

[3]: https://tools.ietf.org/html/rfc1122#section-1.1.3