The TCP/IP protocol suite
TCP - Transmission Control Protocol. A connection-oriented protocol used by most Internet applications to provide a reliable, full-duplex, byte stream for a user process.
UDP - User Datagram Protocol. A connectionless protocol for user processes. Also not reliable.
ICMP - Internet Control Message Protocol. Handles error and control information between gateways and hosts.
IP - Internet Protocol. Provides the packet delivery service for the upper layers.
ARP - Address Resolution Protocol. Maps an Internet address into a hardware address.
RARP - Reverse Address Resolution Protocol.