Page 75 - Intelligent Communication Systems

58 INTELLIGENT COMMUNICATION SYSTEMS
Distributed computing and the prevalence of small computers has reduced the cost
of installation, operation, and maintenance of the LAN.
Each LAN is treated as a component of the global network. A number of local
area networks are interconnected in metropolitan networks. In this way the network
structure is expanded. And through this, a user in the local area network can com-
municate with any users in another local area network via the Internet. The Internet
will be the network infrastructure for everyone in the world.

7.6.2 LAN Topology
In a local area network, coaxial cables, optical fibers, or twisted-pair cables are
mainly used as transmission media. The star, bus, and/or ring topologies are used as
the LAN topology. These three types of LAN topologies are shown in Figure 7.5.
In the star network, each node is linked to the center node. This network is a
typical one in the global network. The center node is common and performs the
switching functions for all. Each node is linked to the center via its transmission
line. The star topology is used mainly in the intraoffice network. Twisted-pair
cables or optical-fiber cables are used as the transmission lines. Its merits are that
it is easy to manage and appropriate for peer-to-peer communications. A dis-
advantage is that it is not reliable, expandable, or flexible, because the center node
performs all of the switching functions—once it goes wrong, the network is in
trouble.

FIGURE 7.5 Three types of LAN topology.