Specifications

Ethernet LAN Standards 3-5
The Open Systems Interconnect (OSI) Model
On the receive side, the MAC layer follows the reverse of the above
steps. It checks the frame for errors, strips control information then
passes the remainder of the packet to the upper layers by way of
logical link control.
• LAYER ONE: Physical Layer–At this layer, the transmission of data
between devices is defined. The definition includes cables and
connectors, connector pinouts, voltage levels that represent digital
logic levels, bit timing, and the actual network interface device called a
Transceiver (transmitter/receiver). The IEEE 802 model divides the
physical layer into four sub-layers: Physical Layer Signaling (PLS),
Attachment Unit Interface (AUI), Physical Medium Attachment
(PMA), and Medium Dependent Interface (MDI).
Figure 3-3. Physical Layer of the OSI Model
- PLS (Physical Layer Signaling)–Defines the signaling and the
interface to the transceiver cable.
- AUI (Attachment Unit Interface)–Defines the transceiver cable
specifications.
- PMA (Physical Medium Attachment)–Defines the transceiver
operation and specifications.
- MDI (Medium Dependent Interface)–Defines the specifications
for the portion of the transceiver that connects to specific cable
types such as 10BASE5 coaxial cable.
The remaining chapters will concentrate primarily on the Physical and
Data Link layers of the OSI Model.
7
6
5
4
3
2
1
PMA
MDI
PLS
AUI
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1. Physical
1913-04