Understanding Network Cabling
of Token Ring networks are offset somewhat by the greater overhead and processing
needs to handle the tokens. Overall, Token Ring networks perform about as fast as
Ethernet networks with similar bandwidth.
IBM invented the Token Ring network technology in the late 1960s, and the
first Token Ring networks started appearing in 1986. While quite a few Token Ring
LANs are installed (running at either 4 Mbps or 16 Mbps), you tend to see them
predominantly in companies that have a strong IBM relationship and, perhaps, also use
an IBM mainframe or minicomputer.
If you're designing a new LAN, generally your best bet is to use Ethernet in a
star topology. You'll find network equipment for this choice is readily available and
inexpensive. Many qualified installers are available for 100Base-T or 1000Base-T.
(There is little sense in installing 10Base-T these days; in fact, the equipment is no
longer available.) As noted earlier, for new networks, you should install Cat-5E cable
at a minimum, even if you're initially going to use 100Base-T, so that you have a ready
upgrade path to the faster standards.
Use Token Ring if some external need is driving this choice, such as connectivity to
an old IBM mainframe that doesn't support Ethernet.
Demystifying Network Cabling
Network cabling can be incredibly confusing. Not only are there many different types
of network cables--all with their own names and properties--but often you can select
different types of cables for a single type of network. For example, Ethernet networks
can use an astonishing number of cables, ranging from coaxial cable, to unshielded
or shielded twisted-pair cable, to fiber-optic cable. To design or support any given
network, you need to know your cable choices and how to maintain the particular type
of cable you select.
The focus in this section is to demystify cabling systems for you. It covers the
most common types of network cable--the kinds that you'll find in 99 percent of the
networks in existence and that you'll use for 99 percent of any new networks. When
appropriate, I will make passing reference to other cable types so that you know what
they are, but you should focus your attention on only a few ubiquitous cable types--
primarily the ones discussed here.
Overview of Basic Cable Types
The most common network cable types are unshielded twisted-pair (UTP) and
coaxial, followed by shielded twisted-pair (STP) and fiber optic. UTP is by far the most
common type in use today.
UTP cable consists of two or more pairs of plastic-insulated conductors inside a
cable sheath (made from either vinyl or Teflon). For each pair, the two conductors are
twisted within the cable, helping the cable resist outside electrical interference. Rigid
standards exist for how this cable is made, including the proper distance between each
twist of the pair. Figure 4-5 shows an example of UTP cable.