Protocols are rules and procedures for the ways we do things. If you speak English, and another person speaks Spanish, but neither of you understand the others native language, than neither of you can communicate. In the sense of computer networking, protocols offer systematic ways as to how data should be handled, as well as how computer systems should communicate over networks and the internet.
The most prevalent networking protocol today is the transport layer protocol suite TCP/IP (Transmission Control Protocol). TCP of the TCP/IP suite is known as a connection-oriented protocol. TCP works by breaking up data into segments and provides sequencing functions to ensure that data is reassembled at the receiving node (computer system) in the order it was sent. TCP relies on IP (Internet Protocol) for addressing and routing functions and is more concerned with how data is packaged for delivery.
TCP works like this: Computer A establishes a connection with computer B using a “3 way handshake”, in which the computer initiating the connection sends a request for connection and the receiving computer sends an acknowledgement that it received the request to connect. Then the computer that made the initial request for connection responds back to the receiving computer with an acknowledgement and a connection is fully established. TCP ads for reliable delivery of data by the use of acknowledgements from both the sender and receiver. This is akin to sending someone a package using certified mail, in which an acknowledgement is sent back to the sender once the package is received.
Many other protocols rely on Transmission Control Protocol in order to pursue their common functions. Some of these protocols are:
The Network layer protocols: IPV4, ICMP (Internet Control Message Protocol), and ARP (Address Resolution Protocol).
The Transport layer protocols: UDP (User Datagram Protocol), and TCP itself.
The Application layer protocols: DNS (Domain Name System), HTTP (Hyper Text Transfer Protocol), Telnet, SMTP (Simple Mail Transport Protocol), and FTP (File Transfer Protocol).
Unlike TCP, UDP (User Datagram Protocol) is a connectionless protocol, and for this reason provides faster data transmission and processing support for network applications and services. It doesn’t rely on the 3 way handshake of TCP. This is the protocol used over xbox live to host online games. Players generally synchronize to a server application or service that hosts the game sending data indiscriminately to and from the server (data may arrive out of order, or data packets may be corrupted or missing at worst). Although it’s not as reliable as TCP, it provides better support for networking services that otherwise would bog down under TCP. With UDP there is no verification that data transmissions were received, it’s up to the upper layer protocols to determine errors or missing data.