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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