Publication date: Aug., 2014
Revision A1
23
This above diagram shows the Ethernet architecture, LLC sub-layer and
MAC sub-layer, which are responded to the Data Link layer, and transceivers, which
are responded to the Physical layer in OSI model. In this section, we are mainly
describing the MAC sub-layer.
3-2. Logical Link Control (LLC)
Data link layer is composed of both the sub-layers of MAC and MAC-client.
Here MAC client may be logical link control or bridge relay entity.
Logical link control supports the interface between the Ethernet MAC and
upper layers in the protocol stack, usually Network layer, which is nothing to do with
the nature of the LAN. So it can operate over other different LAN technology such
as Token Ring, FDDI and so on. Likewise, for the interface to the MAC layer, LLC
defines the services with the interface independent of the medium access
technology and with some of the nature of the medium itself.
The table 3-1 is the format of LLC PDU. It
comprises four fields, DSAP, SSAP, Control and Information. The DSAP address
Coaxial/STP/UTP
IEEE 802.2 LLC
IEEE802.3 CSMA/CD MAC
IEEE 802.3 PLS
ANSI X3T9.5 PMD
CS
IEEE 802.3
MAU
Physical
Layer
Data
Link
Layer
MII
Fiber
Table 3-1 LLC Format
