In the LAN model, the lowest two ISO layers are replaced by three layers:
The Logical Link Control (LLC) Layer
This allows several 'logical' links to exist on the shared medium and
indeed several to exist between a pair of attached systems. Three classes
of LLC are provided:
The service provided by a CO logical links is the same as that provided by
the OSI Datalink layer which assures compatibility between the LAN and WAN
worlds at the Datalink service interface.
Unacknowledged connectionless service.
Connection Oriented service.
Acknowledged connectionless service.
The Medium Access Control (MAC) Layer
This defines the procedure to be used for sharing the medium, for example
CSMA-CD as used in the Ethernet.
The Physical Layer