Data Link Layer - List of Data-link-layer Services

List of Data-link-layer Services

  • Encapsulation of network layer data packets into frames
  • Frame synchronization
  • Logical link control (LLC) sublayer:
    • Error control (automatic repeat request,ARQ), in addition to ARQ provided by some transport-layer protocols, to forward error correction (FEC) techniques provided on the physical layer, and to error-detection and packet canceling provided at all layers, including the network layer. Data-link-layer error control (i.e. retransmission of erroneous packets) is provided in wireless networks and V.42 telephone network modems, but not in LAN protocols such as Ethernet, since bit errors are so uncommon in short wires. In that case, only error detection and canceling of erroneous packets are provided.
    • Flow control, in addition to the one provided on the transport layer. Data-link-layer error control is not used in LAN protocols such as Ethernet, but in modems and wireless networks.
  • Media access control (MAC) sublayer:
    • Multiple access protocols for channel-access control, for example CSMA/CD protocols for collision detection and retransmission in Ethernet bus networks and hub networks, or the CSMA/CA protocol for collision avoidance in wireless networks.
    • Physical addressing (MAC addressing)
    • LAN switching (packet switching) including MAC filtering and spanning tree protocol
    • Data packet queueing or scheduling
    • Store-and-forward switching or cut-through switching
    • Quality of Service (QoS) control
    • Virtual LANs (VLAN)

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