protocolsTCP

protocolsTCP is a term sometimes used to refer to the set of transport-layer protocols built around the Transmission Control Protocol in the Internet protocol suite. The primary protocol in this family is the Transmission Control Protocol (TCP), defined in RFC 793 and refined by later RFCs. TCP provides a reliable, connection-oriented, byte-stream service between applications on hosts communicating over IP networks.

TCP operates above the Internet Protocol (IP) layer and below application protocols such as HTTP, HTTPS, FTP, and SMTP. It ensures data integrity and ordered delivery through sequencing and acknowledgments, and it supports multiplexing via port numbers.

Key mechanisms include a three-way handshake to establish a connection, a termination process to close a connection, and retransmission of segments that time out. The TCP header contains fields such as source and destination ports, sequence and acknowledgment numbers, data offset, flags, window size, checksum, and options. Flags include SYN, ACK, FIN, and RST.

Reliability is achieved through acknowledgments and retransmission. TCP uses flow control via a receiver window and congestion control to modulate the transmission rate based on network conditions. Early algorithms established slow start and congestion avoidance, with enhancements such as fast retransmit/fast recovery and selective acknowledgments (SACK). Modern implementations employ advanced congestion-control variants such as Cubic or BBR and support features like window scaling and timestamp options.

Applications rely on TCP for reliable delivery of streams, including web traffic (HTTP/HTTPS), email (SMTP, IMAP), file transfer (FTP), and remote access (SSH). While widely used, TCP is coupled with security considerations; TLS is commonly layered atop TCP to provide encryption. The term protocolsTCP is not a distinct standard but a shorthand for describing TCP-based transport protocols within the Internet protocol suite.