1.1.4 TCP/IP Model Protocols, Services, and Equipment

The OSI model is a logical model of communications for networked devices and software. The OSI model does not specify the protocols that should be used at each of the seven layers, but it specifies the functionality that should be provided by those protocols. For this reason, you will read and hear statements like “FTP is a Layer 7 protocol” and “TCP is a Transport layer protocol.” These phrases are used to indicate the layers within the OSI model where the protocols operate. The reality, however, is that many protocols and network communications in general do not occur in line with the OSI model. TCP/IP is a perfect example. While we can relate the TCP/IP communications model to the OSI model, it cannot be said to meet the OSI specificati....