Understanding the network.pdf - Back to Home

• Baseband transmission applies the signal voltage directly to the trans
mission medium. As the voltage signal travels across the conductor, the
signal is attenuated. To maintain signal integrity, a repeater is often needed.
Twisted-pair cable is a baseband medium.
• Broadband transmission is used with voltage signals that have been
modulated. By separating the medium's bandwidth into different frequency
channels, multiple signals can be sent across the medium simultaneously.
Coaxial and optical fiber cable can be used as both broadband and baseband
media.
NOTE
The network cable can also act as a broadcast antenna instead of a receiving
antenna. The network cable radiates the carrier signals as they move across the
wire. These signals can be detected and decoded. Network wiring should be exposed
as little as possible in environments where security is a major concern.
Network Topologies
Network devices connect to the transport medium through a transmitter/receiver
called a transceiver. A transceiver can be an external device or can be built into the
device's Network Interface Card (NIC). The pattern in which the network devices
(nodes) are connected together is called the network topology. Network cabling
topology is largely determined by the type of connection medium being used to
connect the nodes. In addition, there is a logical topology that is defined by how the
nodes interact with one another through the transmission media protocol. For
example, it's possible for a collection of hosts to be physically connected in a star
topology but to run as if they're connected as a logical ring. There are three topology
types used in LANs, WANs, and MANs, as discussed in the following sections.
Star Topology
Star topology consists of a central node off which all other nodes are connected by
a single path (see Figure 1.2). A pure star topology is almost never found in a
modern computer network, but modified star or constellation topology is common.