Transmission Control Protocol (TCP) is one of the central protocols of the TCP/IP protocol suite. TCP is responsible at the transport layer for providing a reliable data transmission service. Some of the key features of TCP include:
A less complex, lower overhead alternative at layer four is User Datagram Protocol (UDP), which sacrifices reliability in the name of brevity and speed. Both TCP and UDP are able to form network sockets. The choice of which transport layer protocol is better will vary from application to application.
See RFC 793.