This paper explains the 2 popular reference models: OSI reference model and TCP/IP model, by comparing the functionality of each layer in both models.

Ethernet is a layer 2 data link protocol that is widely used with the TCP/IP protocol, which resides at layers 3 and 4. To understand network communications, it is essential to learn about the ...

As such, a TCP/IP Ethernet frame is an OSI Model Layer 2 PDU. Note that the word datagram is sometimes used interchangeably with PDU or packet in RFCs and commercial documents.

Frame relay didn’t exactly fit the model because it contained some, but not all, of both layers 2 and 3. And TCP/IP didn’t even come close to following the seven layers as specified.