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Chapter 4:
Understanding Network Cabling
By far, the most prevalent bus network used in the past (and in limited existence
today) is one called 10Base-2 Ethernet, or more commonly, Thin Ethernet. This network
type has the following characteristics:
Has a rated maximum speed of 10 Mbps
Uses RG-58/AU or RG-58/CU coaxial cable and BNC connectors
Requires a 50-ohm terminating connector at each end of each segment to function
Can handle a maximum of 30 nodes per segment
Can be run up to a maximum segment length of 185 meters (607 feet)
Can use extended segments through the use of repeaters
Requires each node to be at least 0.5 meter (1.5 feet) of cable distance from any
other node
If repeaters are used, you can connect a maximum of three segments together, and
each segment may have up to 30 nodes (with the repeater counting as a node). You can
also have two additional segments (a total of five) if those extra two segments are used
for distance only and do not have any nodes on them. An entire repeated segment must
never exceed a total of 925 meters (3,035 feet). Remember the 5-4-3 rule: five segments,
four repeaters, three populated segments.
NOTE
Repeaters are hardware devices that electrically boost the signal on a cable so it can be
extended further; they do not route any of the data. In fact, a repeater is "ignorant" of any of the
data it carries. Repeaters are inexpensive and reliable. However, remember that extending a cable
with a repeater means that all the network traffic on one side of the repeater is echoed to the cable
on the other side of the repeater, regardless of whether that traffic needs to go on that other cable.
Repeaters are discussed in more detail in Chapter 6.
Star Topology
A star topology is one in which a central unit, called a hub or concentrator, hosts a set of
network cables that radiate out to each node on the network. Technically, the hub is
referred to as a multistation access unit (MAU), but that particular terminology tends
to be used with only Token Ring networks, which use a logical ring topology (see the
following section). Each hub usually hosts about 24 nodes, although hubs range in size
from 2 nodes up to 96 nodes. Regardless of the hub size, you can connect multiple hubs
together to grow the network in any way that makes sense. See Chapter 6 for more on
connecting hubs together in different configurations. Figure 4-3 shows a simple star
topology network.
All the network traffic used on any of the network connections to the hub is echoed
to all the other connected nodes on that particular hub. Because of this, all the bandwidth
of any single node's connection is shared with all other node's connections. For example,
if one of the nodes connected to the hub is using half the available bandwidth, all the