Sách Local area network overview

15.1 Background
15.2 Topologies and Transmission Media
15.3 LAN Protocol Architecture
15.4 Bridges
15.5 Layer 2 and Layer 3 Switches
15.6 Recommended Reading and Web Site
15.7 Key Terms, Review Questions, and Problems


KEY POINTS
ã A LAN consists of a shared transmission medium and a set of hard-
ware and software for interfacing devices to the medium and regulat-
ing the orderly access to the medium.
ã The topologies that have been used for LANs are ring, bus, tree, and
star. A ring LAN consists of a closed loop of repeaters that allow data
to circulate around the ring. A repeater may also function as a device
attachment point. Transmission is generally in the form of frames. The
bus and tree topologies are passive sections of cable to which stations
are attached. A transmission of a frame by anyone station can be
heard by any other station. A star LAN includes a central node to
which stations are attached.
ã A set of standards has been defined for LANs that specifies a range of
data rates and encompasses a variety of topologies and transmission
media.
ã In most cases, an organization will have multiple LANs that need to be
interconnected. The simplest approach to meeting this requirement is
the bridge.
ã Hubs and switches form the basic building blocks of most LANs.


We turn now to a discussion of local area networks CLANs).Whereas wide
area networks may be public or private, LANs usually are owned by the orga-
nization that is using the network to interconnect equipment. LANs have
much greater capacity than wide area networks, to carry what is generally a
greater internal communications load.
In this chapter we look at the underlying technology and protocol archi-
tecture of LANs. Chapters 16 and 17 are devoted to a discussion of specific
LAN systems.

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