Information Technology Reference
In-Depth Information
outlet.) The TR-to-TR cables are called
backbone wiring
, since they form a unify-
ing structure between TRs. Of course, a very large floor would have more than one
TR, to adhere to the station wire maximums, but the wire between those TRs would
still be referred to as backbone. All the details of this structured wiring concept are
covered later in this chapter.
Cost Factors in Cabling Systems
A variety of methods exist to implement LAN wiring schemes; most methods in
common use will be described in succeeding chapters. These methods vary in three
significant degrees, all of which have cost implications.
First, some LAN topologies require that certain types of wire and connections
be used. For example, the Ethernet 10BaseT can use Category 3 twisted pair and
jacks, while 100BaseTX and 1000BaseT require Category 5e twisted-pair wire and
jacks, and 100BaseFX and 1000BaseSX/LX require the proper mode fiber and con-
nectors. Although your network requirements will frequently dictate which topology
you must use, you may have several choices to make that will influence initial cabling
cost as well as the cost of future expansion. In some cases, it would be possible to
choose an older wiring technology such as 10BaseT on the basis of cost. However,
when you consider the cost of a future upgrade to 100 or 1000 Mbps, a Category 5e
unshielded twisted-pair installation would only support 10 Mbps 10BaseT today, but
100 Mbps 100BaseTX (and Gigabit) for the future. Likewise, you may want to invest
in Category 6 or 7 wiring components to support future upgrades.
Second, LAN wiring methods vary in the extent to which they will support
higher speed network data rates, including future standards that may not be fully
implemented yet. For example, it is probably less expensive to install a Category 5e
cabling system that supports your current need for 10/100 Mbps networking than
it would be to install an advanced Category 6 or 7 facility. Category 5e will support
1000 Mbps on four pairs, but that is its limit. You might never need the
1000/10,000 Mbps (1-10 Gbps) capability, particularly if your facility will be occu-
pied for less than 5 years. What if you had to stay longer? Should you put in
Category 5e jacks and cable to save money, or should you go ahead and install a
Category 6 (or even Category 7) system now, in case the future comes along a little
sooner than expected?
Third, you may choose combinations of cable and connection hardware that
differ in features and cost. This factor may also influence the final, installed cost of
your network cable system. Even among manufacturers that offer products certified
to identical performance ratings, there is a lot of price variation. You may choose a
big-name manufacturer whose cable and connectors cost more than the little guy's.
