What layer of the OSI model does TCP operate on?

TCP, or Transmission Control Protocol, operates at the Transport layer of the OSI (Open Systems Interconnection) model. The Transport layer is responsible for providing reliable data transfer services to the upper layers, which includes error checking, data segmentation, and flow control. TCP specifically ensures that data packets are delivered in sequence and without errors, making it a connection-oriented protocol. This means that before data transmission begins, a connection is established between the sender and receiver to maintain correspondence for the duration of the session.

The Transport layer facilitates communication between applications rather than managing the actual data routes—that function is handled by the Network layer. Unlike the application layer, which is concerned with user interface and application data, the Transport layer focuses on data transfer reliability and flow management, which is where TCP excels. The Data link layer primarily deals with node-to-node data transfer over a single physical link. TCP's role as a part of the Transport layer is critical for ensuring effective and reliable network communication.