TCP (Transmission Control Protocol: see TCP/IP)Transmission Control Protocol is a protocol for delivery of data between hosts in packet-switched computer communication networks. It is one of the key protocols for the transmission of data on the Internet.
TCP is the middle step in three key Internet protocols. Hypertext transfer protocol (HTTP) specifies Web-specific operations, such as the linking of sites. Transmission control protocol (TCP) assures that the blocks of data are sent and received by Web sites in a reliable fashion. And Internet protocol (IP), moves the data packets across the Internet.
The TCP must recover from data that is damaged, lost, duplicated, or delivered out of order. This is achieved by assigning a sequence number to each packet transmitted, and requiring a positive acknowledgment (ACK) from the receiving TCP. If the ACK is not received within a timeout interval, the data is retransmitted. The sequence numbers are used to correctly order segments that may be received out of order and to eliminate duplicates. Damage is handled by adding a checksum to each segment transmitted, checking it at the receiver, and discarding damaged segments.
Other major Internet protocols are Simple Mail Transfer Protocol (SMTP), File Transfer Protocol (FTP), and TELNET Protocol.