The TCP/IP protocol suite includes a number of major protocols and each performs a specific function:

Application Protocols

• Hypertext Transfer Protocol (HTTP) – HTTP governs how files such as text, graphics, sounds, and video are exchanged on the Internet or World Wide Web (WWW). HTTP is an application layer protocol. The Internet Engineering Task Force (IETF) developed the standards for HTTP. HTTP 1.1 is the current version. As its name implies, HTTP is used to exchange hypertext files. These files can include links to other files. A web server runs an HTTP service or daemon (a program that services HTTP requests). These requests are transmitted by HTTP client software, which is another name for a web browser.
• Hypertext Markup Language (HTML) – HTML is a page description language. Web designers use it to indicate to web browser software how the page should look. HTML includes tags to indicate boldface type, italics, line breaks, paragraph breaks, hyperlinks, insertion of tables, and so on.
• Telnet – Telnet enables terminal access to local or remote systems. The telnet application is used to access remote devices for configuration, control, and troubleshooting.
• File Transfer Protocol (FTP) – FTP is an application that provides services for file transfer and manipulation. FTP uses the Session layer to allow multiple simultaneous connections to remote file systems.
• Simple Mail Transport Protocol (SMTP) – SMTP provides messaging services over TCP/IP and supports most Internet e-mail programs.
• Domain Name System (DNS) – DNS provides access to name servers where network names are translated to the addresses used by Layer 3 network protocols. DNS greatly simplifies network usage by end users.

Transport Protocols

• Transmission Control Protocol (TCP) – TCP is the primary Internet protocol for the reliable delivery of data. TCP includes facilities for end-to-end connection establishment, error detection and recovery, and metering the rate of data flow data into the network. Many standard applications such as e-mail, web browsing, file transfer and telnet, depend on the services of TCP. TCP identifies the application using it by a "port" number.
• User Datagram Protocol (UDP) – UDP offers a connection-less service to applications. UDP uses lower overhead than TCP and can tolerate a level of data loss. Network management applications, network file system, and simple file transport use UDP. Like TCP, UDP identifies applications by port number.

Network Protocols

• Internet Protocol (IP) – IP provides source and destination addressing and, in conjunction with routing protocols, packet forwarding from one network to another toward a destination.
• Internet Control Message Protocol (ICMP) – ICMP is used for network testing and troubleshooting. It enables diagnostic and error messages. ICMP "echo" messages are used by the PING application to test if a remote device is reachable.
• Routing Information Protocol (RIP) – RIP operates between router devices to discover paths between networks. In an intranet, routers depend on a routing protocol to build and maintain information about how to forward packets toward the destination. RIP chooses routes based on the distance or "hop count".
• Address Resolution Protocol (ARP) – ARP is used to discover the local address (MAC address) of a station on the network when its IP address is known. End stations as well as routers use ARP to discover local addresses.