Figure 7-2 Example Coaxial Bus Topology
Although new networks are no longer connected in a bus
configuration, some older bus-connected networks do still exist and are still
useful.
Since the early 1990s, the network configuration of choice
has been the star-connected topology, shown in Figure 7-3. The central network
unit is either a multiport repeater (also known as a hub) or a network switch.
All connections in a star network are point-to-point links implemented with
either twisted-pair or optical fiber cable.
Figure 7-3 Example Star-Connected Topology
The IEEE 802.3 Logical Relationship to the ISO Reference
Model
Figure 7-4 shows the IEEE 802.3 logical layers and their
relationship to the OSI reference model. As with all IEEE 802 protocols, the ISO
data link layer is divided into two IEEE 802 sublayers, the Media Access Control
(MAC) sublayer and the MAC-client sublayer. The IEEE 802.3 physical layer
corresponds to the ISO physical layer.
Figure 7-4 Ethernet's Logical Relationship to the ISO
Reference Model
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