Chapter 8 Communications and Networks

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Chapter 8 Communications and Networks
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Chapter 8 Objectives
Discuss the components required for successful
communications
Describe various types of lines for
communications over the telephone network
Describe commonly usedcommunications devices
Describe uses of computer communications
Differentiate among types of networks
Discuss different ways to set upa home network
Explain the purpose ofcommunications software
Identify various physical and wireless
transmission media
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Communications

• What are computer communications?
• Process in which two or more computers
  or devices transfer data, instructions, and
  information

p. 296 Fig. 8-1
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Uses of Computer Communications

• What are some uses of communications technology?

Web
Internet
E-Mail
InstantMessaging
Internet Telephony
Newsgroups
Chat Rooms
WebFolders
Fax Machine or Computer Fax/Modem
VideoConferencing
FTP
p. 298
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Networks

• What is an intranet?

p. 475
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Communications (Telecommunications)

• Communications - transmission of a signal by way
  of a medium
• Signal - contains message comprised of data (0
  1)
• Channel - transmission media on which data travels

Bandwidth is amount of data that can travel over
channel
Transmission media are materials capable of
carrying one or more signals
p. 491
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Communications Devices

• What is a communications device?

p. 312 313 Fig. 8-17
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Transmission Capacities

• Bandwidth - an expression of how much data can be
  sent through a communications channel in a given
  amount of time (measured in bits per second)
• Broadband (fast)
• Any media faster than 1000 Kbps (kilobits per
  second) or 1 Mbps (megabits per second)
• Narrowband (slow)
• Anything below 1000 Kbs or 1 Mbps

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Characteristics of Communications

• Analog signal
• Continuously changes over time
• Digital signal
• At any given time is either high or low
• Signal frequency
• Speed at which signal can change from high to low
  

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Analog vs. Digital Signals
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Communications Channels / Medium

• Wired signal traveling via a physical wire.
• Coaxial
• Twisted pair
• Fiber optics
• Wireless - signals traveling through the air.
• Cellular
• Satellite
• Radio
• Infrared

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Wired Transmission Media

• What is physical transmission media?

• Wire, cable, and other tangible materials used
  to send communications signals

p. 492 Fig. 9-36
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Wired Media

• Twisted-pair cable
• Cable consisting of pairs of twisted wires
• Coaxial cable
• Inner conductor wire surrounded by insulation, a
  conductive shield, and a cover
• Fiber-optic cable
• Thousands of thin strands of glass or plastic
  bound together in a sheathing
• T1 carriers
• Carry twenty-four 64-Kbps signals on one line
• T3 lines
• Carry 672 signals on one line

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Wired Transmission Media

• What are twisted-pair cable and coaxial cable?

• Twisted-pair cable is used for telephone systems
  and network cabling

• Coaxial cable is often used for cable television
  wiring

p. 493 Fig. 9-379-38
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Wired Transmission Media

• What is fiber-optic cable?

• Capable of carrying significantly more data at
  faster speeds than wire cables

• Less susceptible to interference (noise) and,
  therefore, more secure
• Smaller size (thinner and lighter)

p. 493 Fig. 9-39
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Wireless Transmission Media

• What is wireless transmission media?

• Used when inconvenient, impractical, or
  impossible to install cables

p. 494 Fig. 9-40
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Wireless Media

• Microwave transmission
• A high-frequency radio signal that is sent
  through the air
• Communications satellite
• A microwave station placed in outer space
• Wireless fidelity (Wi-Fi)
• Wireless networking devices that use the 802.11
  protocol
• Bluetooth
• Enables digital devices to communicate wirelessly
  over short distances with speeds of up to 1 Mbps
  within range of up to 33 ft
• Infrared transmission
• Sending signals through the air via light wave

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Wireless Transmission Media

• What are broadcast radio and cellular radio?

• Broadcast radio distributes radio signals over
  long and short distances

• Cellular radio is form of broadcast radio used
  for mobile communications

p. 494 Fig. 9-41
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Wireless Transmission Media

• What is a microwave station?

• Earth-based reflective dish used for microwave
  communications

• Must transmit in straight line with no
  obstructions

p. 495 Fig. 9-42
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Wireless Transmission Media

• What is a communications satellite?

• Space station that receives microwave signals
  from earth-based station, amplifies signals, and
  broadcasts signals back to any number of
  earth-based stations

p. 496 Fig. 9-43
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Networks

• What is a network?

• Collection of computers and devices connected via
  communications devices and transmissionmedia

What is a local area network (LAN)?

• Network in limited geographical area such as home
  or office building

• Metropolitan area network (MAN) connects LANs in
  city or town

p. 303 - 304
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Networks

• What is a wide area network (WAN)?

• Network that covers large geographic area using
  many types of media

• Internet is worlds largest WAN

p. 304 Fig. 8-8
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Networks

• What is a client/server network?

• One or more computers act as server and other
  computers, or clients, access server

p. 305 Fig. 8-9
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Home Networks

• What is a home network?

• Multiple computers connected in home
• Several types of home networks
• Ethernet connect computers via cable
• Powerline cable use electrical lines in house
• Phoneline use telephone lines

p. 316 - 317 Fig. 8-22
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Networks

• What is a peer-to-peer network?

• Simple network that connects fewer than 10
  computers

• Each computer, or peer, has equal capabilities

p. 305 Fig. 8-10
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Networks

• What is an intranet?

p. 307
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Communications Over the Telephone Network

• What is the public switched telephone network
  (PSTN)?

• Worldwide telephone system that handles
  voice-oriented telephone calls

p. 310 Fig. 8-15
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Communications Devices

• What are ISDN and DSL modems?

Communications devices that send and receive
digital ISDN and DSL signals
Usually external devices in which one end
connects to a telephone line and the other end
connects to a port on the system unit
p. 314
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Communications Devices

• What is a cable modem?

• Sends and receives data over cable television
  network
• Much faster than dial-up modem or ISDN

p. 314 Fig. 8-18
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Communications Devices

• What is a wireless modem?

• Allows access to the Web wirelessly from a
  notebook computer, a PDA, a smart phone, or other
  mobile device

• Typically use the same waves used by cellular
  telephones

p. 314 Fig. 8-19
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Communications Devices

• What is a network card?

• Adapter card, PC Card, ExpressCard module, USB
  network adapter or flash card that enables a
  computer or device to access a network

p. 315 Fig. 8-20
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Communications Devices

• What is a wireless access point?

• Central communications device that allows
  computers and devices to transfer data wirelessly
  among themselves or to wired network

p. 315