The TCP/IP model was developed by the Department of Defense (DoD) in the 1970s and adopted as the protocol standard for ARPANET in 1983.
TCP/IP is a practical model that is used to communicate with different devices over the internet.
This model does not contain proper documentation. So, most books say that the TCP/IP model holds 5 layers, and some other books say that the TCP/IP model holds 4 layers. But working with a 4-layered or 5-layered TCP/IP model is the same.
As we know, the OSI model holds 7 layers. Layers with Names of TCP/IP are explained in the following diagram.
Naming of TCP/IP Model
The Name of the TCP/IP model is based on 2 protocols of its model. One is TCP protocol, which is used at the Transport layer, and the other is IP protocol, which is used at the Network layer.
As we know, the OSI and TCP/IP models are the same in functionality. So, the protocols, data formats, delivery of data, etc., of TCP/IP layers are just the same as the protocols of OSI layers.
For example, if the protocols of the Transport layer in the OSI model are TCP and UDP, then the TCP/IP model also holds these two protocols for its transport layer.
Layers (5, 6, and 7) in the OSI model combine to make an application layer in the TCP/IP model. So, the Application layer of TCP/IP holds all protocols of Layers 5, 6, and 7 of the OSI model.