Chapter 8 Communications and Networks

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Chapter 8 Communications and Networks
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Communications

• Process in which two or more computers or devices
  transfer data, instructions, and information

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Successful Communications5 components
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Types of Networks

• Collection of computers and devices connected via
  communications devices and transmissionmedia
• Local Area Network (LAN)
• Network in limited geographical areaoffice
  building
• Metropolitan area network (MAN)covers city
• Wide area network (WAN)
• Potentially world-wide coverage
• Internet is the largest WAN

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Types of Networks

• Client/Server

• Peer to Peer
• Simple network that connects fewer than 10
  computers
• Each computer has equal capabilities

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

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Types of Networks

• What is Internet peer-to-peer (P2P)?

• Intranet
• Restricted network usually within an organization
• Allows sharing of organizational-related info
  without putting it out for public reading

• Enables users to connect to each others hard
  disks and exchange files directly

p. 292 Fig. 8-11
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Networks Topology

• Layout of devices in a network
• Bus network
• All computers and devices connect to a central
  cable, or bus

• Ring network
• Cable forms closed ring, or loop, with all
  computers and devices arranged along ring

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Networks Topology

• Star network

• All devices connect to a central device, called
  hub

• All data transferred from one computer to another
  passes through hub

p. 293 Fig. 8-14
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Ethernet and Token Ring Technology

• Ethernet technology allows computers to contend
  for access to network
• If two computers send data at same time, a
  collision occurs and computers must send again

Token ring technology controls access to network
by requiring devices to pass a special signal,
called token
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Networks

• TCP/IP and 802.11

• BlueTooth
• Short-range radio waves transmitdata between
  Bluetooth devices

• TCP/IP (Transmission Control Protocol/Internet
  Protocol) technology transmits data by breaking
  it up into small pieces, or packets
• Commonly used for Internet transmissions
• 802.11 is family of standards for wireless LANs

p. 294
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Networks

• What are IrDA, RFID, and Wireless Applications
  Protocol (WAP)?

Radio Frequency Identification (RFID) uses
radio signals to communicatewith a tag placed in
an object
IrDAspecification allows data to be transferred
wirelessly via infrared light waves
Wireless Applications Protocol (WAP) allow
wireless mobile devices to access Internet
p. 294
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Communications Devices

• What are examples of communications devices?

p. 298
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Using the Telephone System to Communicate

• Public switched telephone network (PSTN)?

• Dial-up line
• Temporary connection using telephone line for
  communications
• Costs no more than making regular call
• Computers at any two locations can establish a
  connection using modems and telephone network

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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
• Sometimes called a broadband modem

p. 300 Fig. 8-19
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Communications Devices

• What is a network card?

• Adapter card, PC Card, or compact flash card that
  enables computer or device to access network

p. 300 Fig. 8-20
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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. 300
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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. 301 Fig. 8-21
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Communications Devices

• What is a router?

• Connects computers and transmits data to correct
  destination on network

• Routers forward data on Internet using fastest
  available path
• Allow messages to flow between networks

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Firewalls

• Program or hardware device that filters
  information coming from Internet connection
• If packet of info is flagged, not allowed through

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Communications Channel

• What is a channel?

• Transmission media on which data travels in
  communications system
• Wire, cable, and other tangible materials used
  to send communications signals

Transmission media are materials capable of
carrying one or more signals
Bandwidth is amount of data that can travel over
channel
p. 303
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Communications Channel

• How is a request sent over the Internet using a
  communications channel?

Step 1. The sending device requests information
using either a physical transmission media or a
wireless transmission media.
Step 2. When the request leaves the ISP, it
travels over T1 lines, microwave stations,
earth-based stations, and communications
satellites until it reaches the Internet backbone.
Step 3. The request travels over T3 lines along
the Internet backbone.
Step 4. The Request travels over T1 lines until
it reaches the destination network server.
p. 304 Fig. 8-24
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Physical 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. 305 Fig. 8-258-26
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Physical 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. 306 Fig. 8-27
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Wireless Transmission Media

• What is wireless transmission media?

• Used when inconvenient, impractical, or
  impossible to install cables
• Includes infrared, broadcast radio, cellular
  radio, microwaves, and communications satellites

p. 306
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Internet Telephony
p. 285
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Uses of Computer Communications

• What are voice mail and wireless messaging
  services?

• Voice mail is voice message converted to digital
  form
• Wireless messaging services include
• Text Messaging
• Instant Messaging
• Picture Messaging

p. 289 Fig. 8-7
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Collaboration and Groupware

• What are collaboration and groupware?

• Collaboration is working with other users
  connected to a server

• Microsoft Office 2003allows collaboration
• Groupware is softwarethat allows peopleto
  shareinformation

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Public Access Points

• Public Internet access point allows wireless
  connection to Internet in public location
• Hot spot

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Global Positioning System
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Verichip (December, 2001)

• Implantable Personal Verification System
• Uses RFID
• Size of a TicTac
• Implanted under the skin
• Immediate ID and retrieval of subscriber supplied
  registry info

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