TCPIPStack

The TCP/IP stack is a suite of communication protocols used for transferring data over the Internet and many other networks. It defines how data is formatted, addressed, transmitted, routed, and received between devices. In most descriptions, the stack is described as four layers: Link, Internet, Transport, and Application.

The link layer encompasses the physical network technologies and framing used on a local network, such as Ethernet or Wi-Fi. The Internet layer provides logical addressing and routing with the Internet Protocol (IP), enabling packets to move between networks. The transport layer offers end-to-end delivery services, primarily the Transmission Control Protocol (TCP), which provides reliable, connection-oriented transmission, and the User Datagram Protocol (UDP), which offers a simpler, best-effort delivery. The application layer contains higher-level protocols used by programs, including HTTP, FTP, DNS, SMTP, and more, often with security extensions such as TLS.

Core protocols include IP (IPv4 and IPv6) for addressing and routing, TCP for reliable streams, UDP for datagrams, ICMP for diagnostics and error reporting, ARP for mapping IP addresses to hardware addresses, and DHCP for dynamic host configuration. Security features may be implemented at various layers, such as TLS for end-to-end encryption in applications or IPsec for network-layer security.

Implementation and scope vary by system. TCP/IP stacks are implemented in operating system kernels, network devices, and embedded systems. Common software stacks appear in BSD-derived, Linux, and Windows environments, and lightweight or specialized implementations (for example, lwIP or uIP) are used in resource-constrained devices. The stack evolved from ARPANET developments in the 1970s and became the foundational protocol suite of the Internet.