Network Protocols

Network Protocols

A network protocol is like a human protocol, except that the entities exchanging messages and taking actions are hardware or software elements of some device (for instance, computer, PDA, cell phone, router, or other network-capable device). All activity in the Internet that engages two or more communicating remote entities is governed by a protocol. For instance, hardware-implemented protocols in the network interface cards of two physically attached computers control the flow of bits on the "wire" between the two network interface cards; congestion-control protocols in end systems control the rate at which packets are transmitted between sender and receiver; protocols in routers decide a packet's path from source to destination. Protocols are running everywhere in the Internet, and as a result much of this blog is about computer network protocols.

As an instance of a computer network protocol with which you are perhaps familiar, think what happens when you make a request to a Web server, that is, when you type the URL of a Web page into your Web browser. The scenario is demonstrated in the right half of "What Is a Protocol" figure. First, your computer will send a connection request message to the Web server and wait for a reply. The Web server will finally 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 page it wants to bring from that Web server in a GET message. Finally, the Web server returns the Web page (file) to your computer.

Given the human and networking examples above, the exchange of messages and the actions taken when these messages are sent and received are the key defining factors of a protocol:

A protocol describes the format and the order of 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 generally, make wide use of protocols. Different protocols are used to complete different communication tasks. As you read through this blog, you will learn that some protocols are simple and straightforward, while others are complicated and intellectually deep. Mastering the field of computer networking is equivalent to understanding the what, why and how of networking protocols.



Tags

network protocol, routers, computer network

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