(^520) PC Hardware: A Beginner’s Guide
Because it uses light and not electrical signals, fiber optic cable is not susceptible to
EMI or RFI, which gives it incredibly long attenuation and maximum segment lengths.
Network backbones commonly use fiber optic cable.
Backbones and Segments
The cable that runs the entire length of a LAN and interconnects all the computers, print-
ers, servers, and other devices of the network is called the backbone. The network back-
bone connects and interconnects all of a network’s resources and serves as the trunk line
for the entire network. Cables commonly used for backbones are 10Base5, 10BaseF,
10BaseT, 100BaseFX, and 100BaseTX.FDDI
Network backbones commonly use Fiber Distributed Data Interface (FDDI) technology.
FDDI is commonly pronounced “F-D-D-I,” but some pronounce it “fiddy.” FDDI is a
100 Mbps fiber optic network access method that is excellent for moving traffic around
the trunk of a network.
FDDI implements networks as two rings. You can attach workstations to one or both
rings of the backbone. The two rings serve as redundant network trunks—if one ring
breaks or fails, the other takes over, routing around the trouble spot. If both rings break,
the remaining pieces bond together to form a new ring.Segments
A segment is a discrete portion of a network, usually represented by a single run of cable,
a grou pof workstations, or even a LAN within a WAN. A cable segment is a single run of
cable with terminators at each end. A network segment is a grou pof workstations, servers,
or devices that are isolated on the other side of a bridge or router to improve the overall
network’s performance or security.Figure 20-7. The makeup of a fiber optic cable