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1-20
Chapter 1
Planning a Network Topology
Work is also proceeding on a 10-Gbps Ethernet standard, products for which
will
surely appear on the market within a few years.
Fast Ethernet Equipment
Although 10-Mbps Ethernet equipment is still widely available, 100-Mbps Fast
Ethernet is currently the industry standard. All Fast Ethernet network
interface
adapters are dual-speed devices, capable of automatically detecting the
current
speed of a network and adjusting themselves to operate at either 10 or 100
Mbps.
Single-speed hubs are still available that run at either 10 or 100 Mbps, but
there
are also dual-speed hubs on the market with the same automatic speed adjust-
ment capability as a dual-speed network adapter.
A Fast Ethernet network requires Category 5 UTP or better, or fiber-optic
cable, but
standard Ethernet requires only Category 3. This is not a major impediment,
however,
because virtually all UTP cable installed today is at least Category 5.
For a typical business LAN, 10 Mbps is usually sufficiently fast to read and
write data
files stored on network servers. However, a heavily trafficked network or
one support-
ing high-bandwidth applications such as streaming audio or video can benefit
from the
100-Mbps Fast Ethernet transmission speed. Despite the fact that many
networks don’t
need the additional bandwidth, Fast Ethernet is the recommended technology
for new
LAN installations today. Fast Ethernet equipment is almost the same price as
standard
Ethernet, and the additional speed provides room for growth in the type of
applica-
tions your network uses.
Tip
Remember that the transmission speed of the LAN usually has little or no
effect on the
users’ Internet access performance. Even the slowest Ethernet LAN, running
at 10 Mbps, is
six times faster than the 1.544-Mbps T-1 connection large organizations
typically use to con-
nect to the Internet.
Gigabit Ethernet is still a relatively new technology, and as a result, it
is still quite
expensive when compared to Fast Ethernet. You use Gigabit Ethernet primarily
for
backbone networks and other applications that require its high speed.
Although virtu-
ally no networks run Gigabit Ethernet to the desktop, it is likely to occur
in the future.
Apart from the cost of the equipment, these different Ethernet speeds also
vary in their
cabling guidelines. Although all forms of Ethernet can still support the
100-meter max-
imum cable length, there are different limitations on the number of hubs
permitted on
a LAN, which is a factor you must consider when designing your network. As
men-
tioned earlier in this lesson, a standard Ethernet LAN can have up to four
hubs, while
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