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Major Protocols in the TCP/IP Suite

This is a chart of the layers of the TCP/IP Suite and the major protocols in each layer. This is not a comprehensive list.

Application Layer

FTP: File Transfer Protocol is for transfering and manipulating files.
SMTP: Simple Mail Transfer Protocol is for sending messages to a mail server for relaying.
POP3: Post Office Protocol version 3 is for retrieving e-mail from a remote server.
Telnet: Telecommunication Network Protocol is for creating a command-line interface on a remote machine.
SNMP: Simple Network Management Protocol is used for network management systems.
DHCP: Dynamic Host Configuration Protocol automates the assignment of IP addresses, subnet masks, default gateway, and other IP parameters.
DNS: Domain Name System translates human meaningful domain names to IP addresses.
HTTP: Hypertext Transfer Protocol is for a user agent such a web browser to retrieve a hypertext document from a server.
IMAP: Internet Message Access Protocol is for retrieving e-mail from a remote server.

Transport Layer

TCP: Transmission Control Protocol works with IP to send a large chunk of data across the Internet by breaking the data into pieces called packets. TCP requests retransmission of lost packets, and reassembles out-of-order packets before it passes that datagram to the application program.
UDP: User Datagram Protocol works with IP to send a large chunk of data across the Internet by breaking the data into pieces called packets. Unlike TCP, UDP does not check for lost lost packets or reassembles out-of-order packets. UDP provides an unreliable transmission service for time-sensitive applications.

Internet Layer

IP: Internet Protocol delivers packets from the source host to the destination host based on their addresses. Forwarding decisions across IP connected networks is typically performed by routers. IP does not check for lost lost packets and so is used with TCP to achieve reliability.
ICMP: Internet Control Message Protocol is used to generate messages in response to errors for instance that a requested service is not available or that a host or router could not be reached.

Link Layer

ARP: Address Resolution Protocol is for finding a host's hardware address when only its IP address is known. It's primarily used to translate IP addresses to Ethernet MAC addresses.
RARP: Reverse Address Resolution Protocol is for finding a host's IP address when only it's MAC address (hardware address) address is known. RARP requires an administrator to maintain a database a database of mappings from IP addresses to MAC addresses on a server.
OSPF: Open Shortest Path First is a routing protocol where each OSPF router collects link state information to construct the entire network topology from which it computes the shortest path for each route.
MAC: Media Access Control is the physical address, a unique serial number assigned to each network adapter.

Computer Networking Sections