segments and backbones
With the various topologies you've looked at, you have seen the words segment and
backbone mentioned a couple of times. A network segment is a cable length (or
multiple cable lengths) that is uninterrupted by network connectivity devices, such
as bridges and routers. It is typical that a single network may be broken into multiple
network segments through the use of a bridge or router to cut down on network
traffic, as shown in Figure 1-12.
In Figure 1-12, notice that there are three network segments named Segment A,
Segment B, and Segment C. Also notice that each network segment could have a
number of clients and servers all connected through a number of hubs that are then
connected to a backbone. This is just one possible solution involving network segments.