Logical Link Control (LLC)

The logical link control (LLC) is the upper sublayer of the data link layer of the open system interconnections (OSI) reference model for data transmission. It acts act an interface between the network layer and the medium access control (MAC) sublayer of the data link layer.

The LLC sublayer is mainly used for its multiplexing property. It allows several network protocols to operate simultaneously within a multipoint network over the same network medium.

LLC Layer in the OSI Model

The Open System Interconnections (OSI) model is a 7 – layered networking framework that conceptualizes how communications should be done between heterogeneous systems. The data link layer is the second lowest layer. It is divided into two sublayers −

  • The logical link control (LLC) sublayer
  • The medium access control (MAC) sublayer

The following diagram depicts the position of the LLC sublayer −

Functions of LLC Sublayer

·         The primary function of LLC is to multiplex protocols over the MAC layer while transmitting and likewise to de-multiplex the protocols while receiving.

·         LLC provides hop-to-hop flow and error control.

·         It allows multipoint communication over computer network.

·         Frame Sequence Numbers are assigned by LLC.

·         In case of acknowledged services, it tracks acknowledgements

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