Transcript Networking Media

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