OSI Model
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Data-Link Layer
The data-link layer provides error-free transfer of data frames from one computer to another over the physical layer. The layers above this layer can assume virtually error-free transmission over the network.
The data-link layer provides the following functions:
- Establishment and termination of logical links (virtual-circuit connection) between two computers identified by their unique network adapter addresses.
- Control of frame flow by instructing the transmitting computer not to transmit frame buffers.
- Sequential transmission and reception of frames.
- Providing and listening for frame acknowledgment, and detecting and recovering from errors that occur in the physical layer by retransmitting non-acknowledged frames and handling duplicate frame receipts.
- Management of media access to determine when the computer is permitted to use the physical medium.
- Delimiting of frames to create and recognize frame boundaries.
- Error-checking of frames to confirm the integrity of the received frame.
- Inspection of the destination address of each received frame and determination of whether the frame should be directed to the layer above.
Note
While the services of the data-link layer provide for reliable delivery of data, many routable protocol suites such as TCP/IP and IPX/SPX do not provide for, nor utilize reliable data-link layer delivery services. Instead, reliable data delivery is provided by protocols operating at the transport layer.
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