The TCP/IP Protocol Suite is used for communication across Networks. The OSI Layer failed due to its incomplete implementation.
The TCP/IP Consists of various protocols in 5 Layered Model.
The Computers along with routers and switches and servers and other computers comprise of Networks all over the World.
Each Layer consists of various protocols that are required for a necessary handshake of communication between two computers.
Each Protocol has a purpose that serves its layer above giving the necessary features to the applications that desire to communicate with other computers.
The Book mentioned is the best book that covers the Subject In Depth.
The Book is all you need to know about Networking.
Data Communications and Networking By Behrouz Forouzan.