Chapter Four

1
Chapter Four

• Networking
• Media

2
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

3
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

4
Data Transmission

• Information can be transmitted via one of two
  methods
• Analog
• Digital
• Amplitude
• A measure of a signals strength

5
Analog Signal

• Uses variable voltage to create continuous waves,
  resulting in an inexact transmission

FIGURE 4-1 Example of an analog signal
6
Digital Signal

• Digital pulses can have a value of 1 or 0

FIGURE 4-2 Example of a digital signal
7
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

8
Data Transmission

• Frequency
• Number of times a signals amplitude changes over
  a period of time
• Expressed in Hertz (Hz)
• Noise
• Interference from sources near network cabling

9
Data Transmission

• Attenuate
• Loss of signal strength as transmission travels
  away from source

FIGURE 4-3 Analog signal distorted by noise and
then amplified
10
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
11
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

12
Media Characteristics

• Throughput and bandwidth
• Cost
• Size and scalability
• Connectors
• Noise immunity

13
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

14
Throughput and Bandwidth
FIGURE 4-5 A comparison of two digital frequencies
15
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

16
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

17
Connectors and Noise Immunity

• Connector
• Connects wire to network device
• Noise Immunity
• Electromagnetic Interference (EMI)
• Radio Frequency Interference (RFI)
• Conduits can protect cabling

18
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

19
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
20
Network Cabling
TABLE 4-1 Types of coaxial cable
21
Network Cabling

• Thicknet (10Base5)
• Thicknet
• Also called thickwire Ethernet
• Rigid coaxial cable used for original Ethernet
  networks
• IEEE designates Thicknet as 10Base5 Ethernet

22
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
23
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
24
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
25
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 pairs
  signals
• Alien Crosstalk occurs when signals from adjacent
  cables interfere with another cables transmission

26
Network Cabling

• Twist Ratio
• Number of twists per meter or foot in a
  twisted-pair cable

FIGURE 4-10 Twisted-pair cable
27
Network Cabling

• Shielded Twisted-Pair (STP)
• Twisted wire pairs are individually insulated and
  surrounded by shielding

FIGURE 4-11 STP cable
28
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
29
Network Cabling

• To manage network cabling, its necessary to be
  familiar with standards used on modern networks,
  particularly Category 3 (CAT3) and Category 5
  (CAT5)

Figure 4-13 CAT5 UTP cable
30
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
31
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
32
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
33
Network Cabling

• Fiber-Optic Cable
• Throughput
• Cost
• Connector
• Noise immunity
• Size and scalability

FIGURE 4-17 SMA fiber connector