LLC (Logical Link Control) IEEE 802.2

In IEEE's version of Ethernet, the top sublayer of Data link layer is Logical Link Control(LLC). LLC's function is performed in software. LLC defines how to multiplex multiple network layer protocols in the data link layer frames. Logical Link Control sublayer performs its multiplexing by using Service Access Point (SAP) identifiers. Logical Link Control sublayer is defined under IEEE 802.2. There are two types of IEEE 802.2 frames. They are:
  1. Service Access Point(SAP)

  2. Subnetwork Access Protocol(SNAP)

Major Duties of Logical Link Control(LLC)
  1. Multiplex multiple network layer protocols in to frames

  2. Sequencing and flow control

IEEE 802.2 uses SAP(Service Access Point) or SNAP(Subnetwork Access Protocol) field to differentiate between encapsulated layer 3 payloads. IEEE 802.2 (LLC) concerns Ethernet, Token Ring and FDDI. To read more about MAC sublayer, visit the link below.
MAC Sublayer IEEE 802.3

Though sequencing and flow control can be done in Logical Link Control Layer, normally this process is done at Transport layer. To read more about different layers in OSI Reference Model, click the link below.
OSI Reference Model

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