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Layer 2 refers to the second layer of the Open Systems Interconnection (OSI) Model, which is the data link layer.
Layer 2 is where data packets are encoded and decoded into actual bits. It is the protocol layer that enables the transfer of data between adjacent network nodes in a network segment, such as a local or wide area network.
Layer 2 provides the procedural and functional means for data transfer between network nodes and provides the means to detect and correct errors that may occur at the physical layer (Layer 1).
Ethernet, which is used for multi-node local area networks (LAN), is the best example of the data link layer protocol. Other protocols include Point-to-Point Protocol (PPP), High-Level Data Link Control (HDLC) and Advanced Data Communication Control Procedures (ADCCP) for dual-node connections.
Layer 2 is mainly concerned with the local delivery of data frames between network devices on the same network or LAN, essentially bringing transmission protocol knowledge into the system, managing physical layer errors and fostering flow control and frame synchronization. It has two sublayers - logical link control (LLC) and media access control (MAC).
Major Layer 2 services include: