TCP (Transmission Control Protocol) is a connection-oriented, reliable transport-layer protocol of the TCP/IP suite that provides process-to-process (end-to-end) communication between applications on hosts.

• Establishes a logical connection first using the three-way handshake before data transfer.
• Provides reliability by sequencing, acknowledgement, retransmission of lost/duplicate segments, and error detection.
• Offers flow control (sliding window) and congestion control (slow start, congestion avoidance).
• Delivers a byte-stream service to the application; uses 20-byte headers and ports for multiplexing.