The OSI model, or Open Systems Interconnection model, is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers. Each layer serves a specific purpose and communicates with the layers directly above and below it. This model helps network engineers understand how data flows through a network and troubleshoot connectivity issues.
The Physical Layer is the foundation of the OSI model. It deals with the actual transmission of raw bits over a physical medium. This layer defines electrical and physical specifications for devices, including voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Examples include Ethernet cables, fiber optic cables, and wireless radio frequencies.
The Data Link Layer is responsible for node-to-node delivery of data. It takes packets from the Network Layer and encapsulates them into frames. This layer provides error detection and correction, flow control, and handles Media Access Control or MAC addresses. Examples include Ethernet, Wi-Fi protocols, and Point-to-Point Protocol. The layer ensures reliable transmission between directly connected nodes.
The Network Layer is responsible for routing packets between different networks. It uses logical addressing through IP addresses to identify devices across networks. This layer determines the best path for data transmission using routing protocols like OSPF, BGP, and RIP. Routers operate at this layer, making decisions about packet forwarding based on routing tables and network topology.