Page 827 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

pronounced as the speed of the transmission increases. It is
recommended that you use shorter cable lengths as the speed of the

transmission increases.

Long cable lengths can often be supplemented through the use of
repeaters or concentrators. A repeater is a signal amplification device,
much like the amplifier for your car or home stereo. The repeater
boosts the signal strength of an incoming data stream and
rebroadcasts it through its second port. A concentrator does the same

thing except it has more than two ports. However, using more than
four repeaters (or hubs) in a row is discouraged (see the sidebar “5-4-3
Rule”).

5-4-3 Rule

The 5-4-3 rule was used whenever Ethernet or other IEEE 802.3
shared-access networks are deployed using hubs and repeaters as

network connection devices in a tree topology (in other words, a
central trunk with various splitting branches). This rule defines the
number of repeaters/concentrators and segments that can be used
in a network design. The rule states that between any two nodes (a
node can be any type of processing entity, such as a server, client,
or router), there can be a maximum of five segments connected by
four repeaters/concentrators, and it states that only three of those

five segments can be populated (in other words, have additional or
other user, server, or networking device connections).

The 5-4-3 rule does not apply to switched networks or the use of
bridges or routers.

An alternative to conductor-based network cabling is fiber-optic
cable. Fiber-optic cables transmit pulses of light rather than

electricity. This gives fiber-optic cable the advantage of being
extremely fast and nearly impervious to tapping and interference.
Fiber will typically cost more to deploy than twisted pair, but its
price premium has decreased to be more in line with other
deployments and is often well worth the expense for its security,
interference resilience, and performance.