Network protocols are similar to a human protocol; except that the entities exchangeing messages and tasking actions are hardware or software components of some device.
All activity in the internet that involves two or more communicating remote entities is govern by a protocol. For example, hardware-implemented protocols in two physically connected computers; control the flow of bits on the “wire” between the two network interface cards. Congestion-control protocols in the end systems control the rate at which packets are transmit between sender and reciever. Protocols in routers determine a packet’s path from source to destination. Protocols are runing everywhere in the Internet.
As an example of a computer network protocols with which you are probably familiar; consider ehat happens when you make a request to a Web server. That is when you type the URL of a Web page into a Web browser. First, your computer will send a connection request to the Web browser and wait for the reply. The Web server will eventually receive your connection request message and return a connection reply message. Knowing that it is now OK to request the Web document; your computer then sends the name of the Web pagevit wants to fetch from the Web server in GET message. Finally, the web server returns th web page (file) to your computer.
The protocol defines the format and the order of the messages exchanged between two or more communicating entities; as well as the actions taken on the transmission and/or receipt of a message or other event.
The Internet, and computer networks in general, make extensive of protocols. Different protocols are used to accomplish different communication tasks. Some protocols are simple and straightforward, while others are complex and intellectually deep. Mastering the field of computer networking is equivalent to understanding of networking protocols.