In information technology, a protocol is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols exist at several levels in a telecommunication connection. There are hardware telephone protocols. There are protocols between each of several functional layers and each corresponding layer at the other end of a communication.

Both end points must recognise and observe a protocol. Protocols are often described in an industry or international standard.
On the Internet, there are the TCP/IP protocols, consisting of:

• Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other Internet points at the information packet level
• Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level
• Additional protocols that are usually packaged with a TCP/IP suite, including the Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere on the Internet