What is TCP?
TCP is a transport protocol that provides an ordered, reliable byte stream between applications. It stands for Transmission Control Protocol. While IP routes packets, TCP helps organize transmission.
Connections and reliability
Endpoints establish a connection before communicating. Data carries sequence information; the receiver acknowledges received portions, and data believed to be missing can be retransmitted. Out-of-order portions are presented to the application in an organized stream. Flow control tries to prevent a fast sender from overwhelming a slow receiver, while congestion control adapts to network capacity. TCP does not preserve message boundaries; applications identify the end of a request using their own format or length information. Port numbers distinguish services on the same device. The connection maintains communication state agreed upon by the client and server.
Uses and limitations
File transfers and many web connections require complete, correctly ordered data. However, waiting for missing portions can introduce delay, and real-time applications may choose other transports. TCP reliability does not mean encryption; confidentiality requires a layer such as TLS. Network delivery also does not prove successful completion of a business operation. For example, receiving a payment request does not remove the need for the application to verify the payment result. Performance analysis should separate connection establishment, packet loss, network latency and server processing time. High bandwidth alone does not imply low latency.