Operation
The LLC sublayer is primarily concerned with:
- Multiplexing protocols transmitted over the MAC layer (when transmitting) and decoding them (when receiving).
- Providing node-to-node flow and error control
In today's networks, flow control and error management is typically taken care of by a transport layer protocol such as the TCP protocol, or by some application layer protocol, in an end-to-end fashion, i.e. retransmission is done from source to end destination. This implies that the need for LLC sublayer flow control and error management has reduced. LLC is consequently only a multiplexing feature in today's link layer protocols. An LLC header tells the data link layer what to do with a packet once a frame is received. It works like this: A host will receive a frame and look in the LLC header to find out to what protocol stack the packet is destined - for example, the IP protocol at the network layer or IPX. However, today most non-IP network protocols are abandoned.
Read more about this topic: Logical Link Control
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