What is layer 2? - Definition from Whatis.com

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layer 2

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layer 2

Layer 2 refers to the Data Link layer of the commonly-referenced multilayered communication model, Open Systems Interconnection (OSI). The Data Link layer is concerned with moving data across the physical links in the network. In a network, the switch is a device that redirects data messages at the layer 2 level, using the destination Media Access Control (MAC) address to determine where to direct the message.

The Data-Link layer contains two sublayers that are described in the IEEE-802 LAN standards:

Media Access Control (MAC) sublayer
Logical Link Control (LLC) sublayer

The Data Link layer ensures that an initial connection has been set up, divides output data into data frames, and handles the acknowledgements from a receiver that the data arrived successfully. It also ensures that incoming data has been received successfully by analyzing bit patterns at special places in the frames.

Related glossary terms: TP0-TP4 (transport protocols 0 to 4), physical layer, Transport Services Access Point (TSAP), Media Access Control layer (MAC layer), Layer Two Tunneling Protocol (L2TP), data link layer, OSI (Open Systems Interconnection), CDPD (Cellular Digital Packet Data), presentation layer, Application layer

This was last updated in October 2006

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