Chapter One - Mercer University
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Transcript Chapter One - Mercer University
Chapter Four
Networking
Media
Chapter Objectives
Explain concepts related to data
transmission and noise
Describe the physical characteristics of
coaxial cable, STP, UTP, and fiber-optic
media
Explain the benefits and limitations of
different networking media
Chapter Objectives
Identify the best practices for cabling
buildings and work areas
Describe the methods of transmitting data
through the atmosphere
Identify the network media best suited to
specific LAN environments
Data Transmission
Information can be transmitted via one of
two methods
– Analog
– Digital
Amplitude
– A measure of a signal’s strength
Analog Signal
Uses variable voltage to create continuous waves,
resulting in an inexact transmission
FIGURE 4-1 Example of an analog signal
Digital Signal
Digital pulses can have a value of 1 or 0
FIGURE 4-2 Example of a digital signal
Data Transmission
Binary system encodes using 1s and 0s
Bits can only have a value of either 1 or 0
Eight bits together form a byte
Data Transmission
Frequency
– Number of times a signal’s amplitude changes
over a period of time
– Expressed in Hertz (Hz)
Noise
– Interference from sources near network cabling
Data Transmission
Attenuate
– Loss of signal strength as transmission travels away
from source
FIGURE 4-3 Analog signal distorted by noise and then amplified
Data Transmission
Regeneration
– Process of retransmitting a digital signal
Repeater
– Device used to regenerate a signal
Figure 4-4 Digital signal distorted by noise and then repeated
Data Transmission
Modem
– Name reflects function as modulator/demodulator
– Modulates analog signals into digital sounds at
the transmitting end for transmission over
telephone lines
– Demodulates digital signals into analog signals
at the receiving end
Media Characteristics
Throughput and bandwidth
Cost
Size and scalability
Connectors
Noise immunity
Throughput and Bandwidth
Throughput is the amount of data the medium
can transmit during a given period of time
– Also called capacity
Bandwidth measures the difference between the
highest and lowest frequencies a media can
transmit
– Range of frequencies is directly related to throughput
Throughput and Bandwidth
FIGURE 4-5 A comparison of two digital frequencies
Cost
Cost of installation
Cost of new infrastructure versus reusing
existing infrastructure
Cost of maintenance and support
Cost of a lower transmission rate affecting
productivity
Cost of obsolescence
Size and Scalability
Specifications determining size and scalability
– Maximum nodes per segment (dependent on
attenuation)
– Maximum segment length
– Maximum network length
Latency is the delay between the transmission
of a signal and its receipt
Connectors and Noise Immunity
Connector
– Connects wire to network device
Noise Immunity
– Electromagnetic Interference (EMI)
– Radio Frequency Interference (RFI)
– Conduits can protect cabling
Network Cabling
Baseband and Broadband Transmission
– In baseband transmission, digital signals are sent
through direct current (DC) pulses applied to the
wire
– In broadband transmission, signals are
modulated as radio frequency (RF) analog pulses
that use different frequency ranges
Network Cabling
Coaxial Cable
– Central copper core
surrounded by an
insulator
– Braiding insulates
coaxial cable
– Sheath is the outer
cover of a cable
– Foundation for
Ethernet network in
the 1980s
FIGURE 4-6 Coaxial cable
Network Cabling
TABLE 4-1 Types of coaxial cable
Network Cabling
Thicknet (10Base5)
– Thicknet
• Also called thickwire Ethernet
• Rigid coaxial cable used for original Ethernet
networks
– IEEE designates Thicknet as 10Base5 Ethernet
Network Cabling
Thicknet (10Base5)
–
–
–
–
–
Throughput
Cost
Connector
Noise immunity
Size and
scalability
FIGURE 4-7 Thicknet cable transceiver with detail of a vampire tap
piercing the core
Network Cabling
Thinnet (10Base2)
Also known as thin
Ethernet, was most
popular medium for
Ethernet LANs in the
1980s
–
–
–
–
–
Throughput
Cost
Size and scalability
Connector
Noise Immunity
FIGURE 4-8 Thinnet BNC connectors
Network Cabling
Signal Bounce
– Caused by
improper
termination
– Travels
endlessly
between two
ends of network
– Prevents new
signals from
getting through
FIGURE 4-9 Typical coaxial network using
a bus topology
Network Cabling
Twisted-Pair (TP) Cable
– Similar to telephone wiring
– Consists of color-coded pairs of insulated copper wires
twisted around each other and encased in plastic
coating
– Twists help reduce effects of crosstalk, interference
caused by signals traveling on nearby wire pairs
infringing on another pair’s signals
– Alien Crosstalk occurs when signals from adjacent
cables interfere with another cable’s transmission
Network Cabling
Twist Ratio
– Number of
twists per meter
or foot in a
twisted-pair
cable
FIGURE 4-10 Twisted-pair cable
Network Cabling
Shielded Twisted-Pair (STP)
– Twisted wire pairs are individually insulated and
surrounded by shielding
FIGURE 4-11 STP cable
Network Cabling
Unshielded Twisted-Pair
– Consists of one or more insulated wire pairs encased in a
plastic sheath
– Does not contain additional shielding
FIGURE 4-12
UTP cable
Network Cabling
To manage network cabling, it’s necessary to be familiar
with standards used on modern networks, particularly
Category 3 (CAT3) and Category 5 (CAT5)
Figure 4-13
CAT5 UTP
cable
Network Cabling
STP and UTP
– Throughput
– Cost
– Connector
– Noise immunity
– Size and
scalability
FIGURE 4-14 RJ-45 connector, used by
both STP and UTP
Network Cabling
Fiber-Optic Cable
– Contains one or
several glass
fibers at its core
– Cladding is the
glass shield
around the core
FIGURE 4-15 Fiber-optic cable
Network Cabling
Single-Mode Fiber
– Carries single
frequency of light
to transmit data
Multimode Fiber
– Carries many
frequencies of light
over a single or
many fibers
FIGURE 4-16 Single-mode and
multimode fiber-optic cables
Network Cabling
Fiber-Optic Cable
– Throughput
– Cost
– Connector
– Noise immunity
– Size and scalability
FIGURE 4-17 SMA fiber connector