Chapter 9 Communications and Networks

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Chapter 9Communications and Networks
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Communications

• What is computer communications?

• A process in which one computer transfers data,
  instructions, and information to another
  computer(s)

p.9.2 Fig. 9-1
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Communications

• What is needed for successful communications?

p.9.2
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Communications

• What is the primary function of a communications
  device?

• To convert or format signals so they are suitable
  for the communications channel or a receiving
  device

p.9.3 Fig. 9-2
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Sending and Receiving Devices

• What is a sending and receiving device?

• Initiates or accepts transmission of data,
  instructions, and information

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Sending and Receiving Devices

• What are some specialized sending and receiving
  devices?

p.9.3 Fig. 9-3
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Uses of Communications Technologies

• What are some uses of communications technology?

• Communications technology use is all around you

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Uses of Communications Technologies

• What is groupware?

• A software application that helps groups of
  people work together on projects and share
  information over a network
• A component of workgroup computing
• includes network hardware and software that
  enables group members to work together
• Most groupware provides personal information
  manager (PIM) functions

p.9.10
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Uses of Communications Technologies

• What is a global positioning system (GPS)?

• Consists of one or more earth-based receivers
  that accept and analyze signals sent by
  satellites in order to determine the receivers
  geographic location

Where am I?
p.9.10 Fig. 9-8
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Uses of Communications Technologies

• What is Digital Angel?

• A computer chip containing a GPS device
• Worn as a bracelet or woven into fabric that has
  an antenna that communicates with the GPS
  satellite
• Measures and sends biological information to the
  satellite

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Networks

• What is a network?

• A collection of computers and devices connected
  by communications channels
• Facilitates communications among users and allows
  users to share resources with other users

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Networks

• What is a site license?

• A legal agreement that allows multiple users to
  run a software package simultaneously
• License fee usually is based on the number of
  users or the number of computers attached of the
  network

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Networks

• What is a local area network (LAN)?

• A network that connects computers and devices in
  a limited geographical area such as a home,
  school computer laboratory, office building, or
  closely positioned group of buildings

Click to view Web Link then click LAN
p.9.12 Fig. 9-9
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Networks

• What is a node ?

• Each computer or device on a network

node
node
node
node
p.9.12
node
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Networks

• What is a network operating system?

• The system software that organizes and
  coordinates the activities on a local area
  network
• Also called a network OS or NOS

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Networks

• How do some popular operating systems support
  networks ?

• Many operating systems have built-in network
  features
• In other cases, the network OS is a set of
  programs that works with another operating
  system(s)

p.9.12 Fig. 9-10
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Networks

• What is a peer-to-peer LAN?

• A simple, inexpensive network that typically
  connects less than 10 computers together
• Each computer on a peer-to-peer network can share
  the hardware, data, or information located on any
  other computer in the network
• Each computer stores files on its own storage
  devices

p.9.13 Fig. 9-11
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Networks

• What is a client/server LAN?

• A network in which one or more computers act as a
  server and the other computers on the network can
  request services from the server

p.9.14 Fig. 9-12
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Networks

• What are servers and clients?

• Server
• Controls access to the hardware and software on
  the network
• Provides a centralized storage area for programs
• Dedicated servers perform a specific task

• Clients
• Other computers on the network
• Rely on the server for resources

p.9.14
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Networks

• What is a wide area network (WAN)?

communications satellite

• A network that covers a large geographic area
  using a communications channel that combines many
  types of media
• Can be one large network or can consist of two or
  more LANs connected together
• The Internet is the worlds largest WAN

Click to view Web Link then click Wide Area
Network
p.9.15 Fig. 9-13
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Networks

• What is an Internet use of peer-to-peer (P2P)?

• An Internet network that enables users with the
  same networking software to connect to each
  others hard disks and exchange files directly
• Napster and Gnutella are two examples of P2P

p.9.16 Fig. 9-14
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Networks

• What is a metropolitan area network (MAN)?

• A backbone network that connects local area
  networks in a metropolitan area such as a city or
  town
• Handles the bulk of communications activity, or
  traffic, across that region

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Networks

• What is a network topology?

• The configuration, or physical arrangement, of
  the devices in a communications network
• Networks usually use combinations of three
  topologies

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Networks

• What is a bus network?

• Consists of a single central cable, to which all
  computers and other devices connect
• The bus is the physical cable
• The bus is also called the backbone
• Inexpensive and easy to install

personal computer
personal computer
personal computer
p.9.17 Fig. 9-15
personal computer
personal computer
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Networks

• What is a ring network?

• A cable forms a closed ring, or loop, with all
  computers and devices arranged along the ring
• Data travels from device to device around the
  entire ring, in one direction
• If a device fails, all the devices before the
  failed device are unaffected, but those after the
  failed device cannot function

p.9.16 Fig. 9-16
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Networks

• What is a star network?

• All of the devices connect to a central computer
• The central computer is called the hub
• All data that transfers from one computer to
  another passes through the hub

personal computer
personal computer
personal computer
host computer
personal computer
p.9.17 Fig. 9-17
printer
file server
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Networks

• What are network communications technologies?

• Specific combinations of hardware and software
  that allow the different devices on several types
  of networks to be able to communicate

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Technology Trailblazer

• Robert Metcalfe

• The inventor of Ethernet
• Founder of 3Com Corporation
• Former publisher and a current InfoWorld magazine
  columnist

Click to view Web Link then click Robert
Metcalfe
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Networks

• What is Ethernet?

• A LAN technology that allows personal computers
  to contend for access to the network
• Based on a bus topology, but can be wired in a
  star pattern
• The most popular LAN because it is relatively
  inexpensive and easy to install and maintain

Click to view Web Link then click Ethernet
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Networks

• What is token ring?

• A LAN technology that controls access to the
  network by requiring that network devices share
  or pass a special signal, called a token
• A token is similar to a ticket
• The device with the token can transmit data over
  the network
• Only one token exists per network
• Based on a ring topology, although it can use a
  star topology

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Networks

• What is TCP/IP?

• Short for transmission control protocol/Internet
  protocol
• A technology that manages the transmission of
  data by breaking it up into packets
• Commonly used for Internet transmissions

Click to view Web Link then click TCP/IP
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Networks

• What is the Wireless Applications Protocol (WAP)?

• Allows wireless mobile devices to access the
  Internet and its services such as the Web and
  e-mail
• Uses a client/server network
• The wireless device contains the client
  software, which connects to the Internet
  service provider's server
• Devices that support WAP are called WAP-enabled
  devices

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Networks

• What is an intranet?

• An internal network that uses Internet
  technologies
• Generally makes company information accessible to
  employees and facilitate working in groups
• Typically also includes a connection to the
  Internet

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Networks

• What is an extranet?

• Allows customers or suppliers to access part of a
  companys intranet

p.9.20 Fig. 9-18
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Networks

• What is a firewall?

• A general term that refers to hardware and/or
  software that restricts access to data and
  information on a network

printer
personal computer
personal computer
corporate network
personal computer
Internet
firewall
personal computer
personal computer
p.9.20 Fig. 9-19
personal computer
personal computer
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Communications Software

• What is communications software?

• Consists of programs that help you establish a
  connection to another computer or network
• Manages the transmission of data, instructions,
  and information
• For two computers to communicate, they must
  have compatible communications software
• Often, separate communications programs on your
  computer each serve a different purpose

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Communications Software

• What is file transfer protocol (FTP)?

• An Internet standard that allows you to upload
  and download files to and from a Web server,
  called the FTP server
• An anonymous FTP site allows anyone to transfer
  files
• Other sites require a specific username and
  password to access the FTP server

Click to view Web Link then click FTP Programs
p.9.24 Fig. 9-23
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The Telephone Network

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

• The worldwide telephone system that handles
  voice-oriented telephone calls

satellite
Click to viewanimation
p.9.25 Fig. 9-24
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The Telephone Network

• What is a dial-up line?

• A temporary connection that uses one or more
  analog telephone lines for communications
• Not permanent
• A modem at the sending end dials the telephone
  number of a modem at the receiving end

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The Telephone Network

• What is a dedicated line?

• A connection that always is established between
  two communications devices
• The quality and consistency of the connection is
  better than a dial-up line because dedicated
  lines provide a constant connection

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The Telephone Network

• What is transfer rate?

• The speed with which a line carries data and
  information
• The faster the transfer rate, the faster you can
  send and receive data and information
• Usually are expressed as bits per second (bps)

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The Telephone Network

• What is an ISDN line?

• Integrated Services Digital Network
• A set of standards for digital transmission of
  data over standard copper telephone lines
• Telephone line can carry three or more signals at
  once, through the same line using a technique
  called multiplexing

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The Telephone Network

• What is DSL?

• Digital subscriber line
• Transmits at fast speeds on existing standard
  copper telephone wiring
• Some installations can be used for both voice and
  data
• Requires a special network card or DSL modem
• ADSL (asymmetric digital subscriber line)
  supports faster transfer rates when receiving
  data than when sending data

Click to view Web Link then click DSL
p.9.26 Fig. 9-26
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The Telephone Network

• What is a T-carrier line?

• Any of several types of digital lines that carry
  multiple signals over a single communications
  line
• Uses a technique called multiplexing so that
  multiple signals can share the telephone line
• Provides extremely fast data transfer rates
• Usually only affordable by medium to large
  companies

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The Telephone Network

• What is asynchronous transfer mode (ATM)?

• A service that carries voice, data, video, and
  multimedia at extremely high speeds
• Predicted to become the Internet standard for
  data transmission

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Communications Devices

• What is a communications device?

• Any type of hardware capable of transmitting
  data, instructions, and information between a
  sending device and a receiving device
• Sometimes the device must convert the data,
  instructions, and information from analog to
  digital signals or vice versa

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Communications Devices

• What is a modem?

• A communications device that converts a
  computer's digital signals to analog signals
  before they are transmitted over standard
  telephone lines
• Sometimes called a dial-up modem

Click to view Web Link then click Modems
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Communications Devices

• What is a network interface card (NIC)?

• Also called a LAN adapter
• A card you insert into an expansion slot of a
  personal computer or other device, enabling the
  device to connect to a network
• Works with a particular network technology
• Available for desktop and mobile computers

NIC for desktop computer
Click to view Web Link then click Network
Interface Cards
NIC for notebook computer
p.9.29 Fig. 9-29
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Communications Devices

• What is a hub?

• A device that provides a central point for cables
  in a network

p.9.30 Fig. 9-30
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Communications Channel

• What is a channel?

• The communications path between two devices

Click to view Web Link then click Bandwidth
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Communications Channel

• What are characteristics of transmission media?

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Physical Transmission Media

• What is physical transmission media?

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

p.9.32 Fig. 9-32
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Physical Transmission Media

• What is twisted-pair cable?

• Consists of one or more twisted pair wires
  bundled together
• Each twisted pairwire consists of two separate
  insulated copper wires
• Twisted together to reduce noise
• Noise is an electrical disturbance that can
  degrade communications

p.9.33 Fig. 9-33
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Physical Transmission Media

• What is coaxial cable?

• Consists of a single copper wire surrounded by at
  least three layers
• Often called coax
• Often used for cable television wiring

p.9.33 Fig. 9-34
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Physical Transmission Media

• What is fiber-optic cable?

• Contains a core of dozens or hundreds of thin
  strands of glass or plastic
• Uses light to transmit signals
• Each strand is called an optical fiber
• Thin as a human hair

p.9.34 Fig. 9-35
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Physical Transmission Media

• What are the advantages and disadvantages of
  fiber-optic cable?

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Wireless Transmission Media

• What is wireless transmission media?

• Send communications signals through the air or
  space
• Used when it is inconvenient, impractical, or
  impossible to install cables

Click to view video
p.9.34 Fig. 9-36
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Wireless Transmission Media

• What is Bluetooth?

• Uses short-range radio waves to transmit data
  among Bluetooth-enabled devices
• Device contains a small chip that allows it to
  communicate with other Bluetooth-enabled
  devices

p.9.35 Fig. 9-37
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Wireless Transmission Media

• What is cellular radio?

• A form of broadcast radio that is used widely for
  mobile communications, specifically wireless
  modems and cellular telephones
• A cellular telephoneis a telephone device that
  uses radio signals to transmit voice and
  digital data messages

mobile telephone switching office (MTSO)
calling party in auto
cell
public switched telephone network
cell
cell
base station (microwave station)
cell
p.9.36 Fig. 9-39
called party
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Wireless Transmission Media

• What are microwaves?

• Radio waves that provide a high-speed signal
  transmission
• Involves sending signals from one microwave
  station to another

p.9.38 Fig. 9-40
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Wireless Transmission Media

• What is a microwave station?

• An earth-based reflective dish that contains the
  antenna, transceivers, and other equipment
  necessary for microwave communications
• Uses line-of-sight transmission
• Must transmit in a straight line with no
  obstructions between microwave antennas

p.9.38 Fig. 9-40
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Wireless Transmission Media

• What is a communications satellite?

• A space station that receives microwave signals
  from an earth-based station, amplifies the
  signals, and broadcasts the signals back over a
  wide area to any number of earth-based stations
• Transmission to a satellite is an uplink
• Transmission from a satellite to an earth-based
  station is a downlink

Click to view video
p.9.38 Fig. 9-41
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Wireless Transmission Media

• What is infrared (IR)?

• A wireless transmission media that sends signals
  using infrared light waves
• Requires a line-of-sight transmission
• Many computers and devices have an IrDA port that
  enables the transfer of data using infrared light
  rays

Click to view video
p.9.39 Fig. 9-42