Duties of IEEE 802.2 Logical Link Control (LLC)

In IEEE's version of Ethernet, the top sublayer of the Data link layer is Logical Link Control(LLC).

LLC' performs its functions in the software part of the Data Link Layer. LLC defines how to multiplex multiple network layer protocols in the data link layer frames. So, any logical operation in the Data Link Layer is happening in LLC.

Let us check the IEEE definition of Logical Link Control(LLC). Logical Link Control sublayer comes 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)

Logic Link Control (LLC) has a few duties in the OSI reference model. Let us check them.

1. Multiplex multiple network layer protocols into frames.

2. The second duty is Sequencing and flow control.

IEEE 802.2 uses the SAP(Service Access Point) or SNAP(Subnetwork Access Protocol) field to differentiate between encapsulated layer three payloads.

IEEE 802.2 (LLC) concerns Ethernet, Token Ring, and FDDI. To read more about the MAC sublayer, visit the link below.

Though LLC can do the sequencing and flow control, the Transport layer does it better. Let me explain how different the LLC and Transport Layer are in sequencing and flow control. LLC is limited to the same LAN. It does not work outside the LAN. To read more about different layers in the OSI Reference Model, click the link below.