TCP/IP protocols are managed into five basic layers. Although some layers of the TCP/IP reference model related to layers of the ISO reference model, the ISO layers procedure does not have a layer that corresponds to TCP/IP Internet Layer.

TCP/IP reference model is given in the figure below.

LAYER 1:

Corresponds to physical network hardware layer in OSI.

LAYER 2:

Specifies how to manage data in frames.

LAYER 3:

Specifies the format of data packets transmit across an Internet and forwards data packets.

LAYER 4:

Specifies how to ensure reliable communication.

LAYER 5:

Like 6 and 7 in OSI architecture, it specifies how one application needs an Internet.

HOST COMPUTERS, ROUTERS AND PROTOCOL LAYERS:

TCP/IP describe the term host computer to refer to any computer machine that connects to an Internet and executes applications. A TCP/IP protocol makes it worth full for any pair of hosts to interact despite hardware differences.

Both routers and host require TCP/IP protocol software but routers do not require layer 5 protocols for applications, as they do not execute applications.