The TCP protocol operates on layer 4, the Transport layer of the OSI model.
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet Protocol Suite and the Open Systems Interconnection (OSI). The protocols of the layer provide host-to-host communication services for applications. It provides services such as connection-oriented data stream support, reliability, flow control, and multiplexing.
The details of implementation and semantics of the Transport Layer of the TCP/IP model (RFC 1122), which is …