1. Communications and Networks
Chapter 9
Communications and Networks

2. Competencies (Page 1 of 2)
Discuss connectivity, the wireless revolution, and communication systems
Describe physical and wireless communications channels
Discuss connection devices, and services including dial-up, DSL, cable, satellite and cellular.
Describe data transmission factors, including bandwidths and protocols
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3. Competencies (Page 2 of 2)
9-3
Competencies (Page 2 of 2)
Discuss networks and key network terminologies.
Describe different types of networks, including local area, metropolitan area, and wide area networks.
Describe network topologies, including configurations and strategies.
Describe organization- al uses of Internet technologies, include- ing intranets, extranets, and firewalls.
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4. Introduction
Cell phones and other wireless technologies are allowing us to stay connected in today’s world like never before. Increased connectivity potentially means increased productivity especially in the business world. You will learn more about the concept of connectivity and the impact of the wireless revolution in this chapter.
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5. 9-5
Communications
Ask students to give examples of communication devices that they use daily
The process of sharing data, programs, and information between two or more computers
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6. 9-6
Communications Today
Numerous applications depend on communication systems— , Instant messaging (IM), Internet telephone, and Electronic commerce
Connectivity uses computer networks to link people and resources
Going wireless has been the most dramatic change
Connectivity is a concept related to using computer networks to link people and resources
Microcomputers. minicomputers, and mainframes can all be connected
Wireless revolution
Use of mobile or wireless devices
The revolution is the support of more than just the wireless telephone
Many devices can and will connect to one another without any physical connection
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7. Communication Systems
9-7
Communication Systems
Four basic elements
Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
Electronic systems that transmit data from one location to another
Communication systems can be wired or wireless
Basic elements
Sending and receiving devices – computer or a specialized communication device
Communication channel – carries the message
Connection devices – act as an interface between sending and receiving devices; convert outgoing messages into packets (key term) that can travel across the communication channel
Data transmission specifications – rules and procedures that coordinate the sending and receiving devices
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8. Communication Channels
Channels carry data from one computer to another
Two categories of communication channels
Physical connection
Wireless connection
Channels are essential to a communication system
They carry data
Types of channels
Telephone lines (key term)
Coaxial cables(key term)
Fiber-optic cable (key term)
Infrared (key term)
Broadcast radio (key term)
Microwave (key term)
Satellite (key term)
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9. Physical Connections Ethernet cable (Twisted pair cables)
Coaxial cable
Fiber-optic cable
Ethernet cable – consists of twisted pair cable; slowest; being phased out by more advanced and reliable media
Coaxial cable – single solid copper core; 80 times transmission of twisted pair; television and computer networks
Fiber optic – 26,000 times capacity of twisted pair cable; more secure and reliable; best over limited distances; lighter, more reliable, and less expensive than coaxial cable
Craig -- please ask photo researcher to locate a photo of an Ethernet cable – to replace the top item (telephone line).
Return
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10. Wireless Connections Infrared Radio frequency (RF)
9-10
Wireless Connections
Infrared
Radio frequency (RF)
Wi-Fi (wireless fidelity)
Microwave
Stations
Satellite
GPS
Microwave dish
Wireless connections do not use a solid substance to connect; uses the air itself
Types of wireless connections are:
Infrared
Light waves used over short distances
Sometimes called line of sight communications
Sending and receiving devices must be in clear view of one another
Broadcast radio
Uses towers called transceivers (key term)
Web-enabled devices follow a standard known as Wi-Fi (wireless fidelity)
Microwave
Uses high-frequency radio waves
Also line of sight
Used for short distances
Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations; many of these offered by Intelsat, the International Telecommunications Satellite Consortium which is owned by 114 governments and forms a worldwide communications system
Satellites can be used to send and receive data; Uplink
is sending data to satellite and Downlink refers to receiving data from a Satellite
GPS (Global Positioning system) use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth
Satellite
GPS
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11. Communication Channels Summary
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12. Connection Device Signals
Types of signals
Analog
Digital
Signals
Sent analog – telephone signals; continuous electronic wave
Sent digital – computer signals; presence or absence of an electronic pulse; on/off
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13. Connection Device Types and Transfer Speeds
Types of modems
External
Internal
PC Card
Wireless
Modem – modulator-demodulator
Modulation (key term) is the name of the process for converting from digital to analog
Demodulation (key term) is the name of the process for converting from analog to digital
External – stands apart from the computer is typically connected with a cable
Internal – built into the computer system unit already
PC card – credit card-size expansion board that is inserted into portable computers; telephone cable connects the modem to the telephone wall jack
Wireless modem (key term) may be external, internal, or a PC card
Does not use cables
Signals are sent through the air
Transfer Speed or transfer rate (key term)-measured in bits per second (key term); the higher the speed the faster the transfer rate
Transfer Speeds
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14. Connection Service Dial-Up services Leased lines – T1, T2, T3 and T4
Digital subscriber line (DSL)
Uses existing phone lines
One type widely used is ADSL
Cable
Uses existing TV cable
Provides speeds as fast as DSL at a lower cost
Satellite/air connection services
Seven times faster than dial-up
Slower than DSL & cable modem
Cellular Services
Alternative for mobile devices and laptops
Current service areas limited
Standard telephone lines and conventional modems use a dial-up service
Slow
Still popular, but many are using other types of connections
T1, T2, T3, and T4 leased lines – do not require conventional modems and provide very high capacity and is expensive—mainly used by corporations not typical end user; T1 lines provide a speed of 1.5 mbps (mega bits per second)(key term) which is over 26 times as fast as a conventional modem
DSL – uses existing telephone lines to provide high-speed connections; uses DSL modems
Cable – Cable connections reach 90% of homes in America but not all cable companies support cable modems presently
Satellite/air connection services – Uses just what it says—satellite and air connections; older satellites couldn’t upload and dial up was still used for the process; but newer satellites are two-way satellites capable of handling both uploading and downloading; available almost anywhere but slower than DSL
Cellular services – option for mobile devices and laptops using 3G cellular networks (key term) – current access is limited but growing – download speed 400 – 700 Kpbs and upload at 50 Kbps – future service to have speeds equal to DSL
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15. Typical User Connection Costs & Speeds
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16. Bandwidth Measurement of the capacity of the channel Categories
Voice band also known as low bandwidth
Medium band
Broadband
Used for high capacity transmission
Used by DSL, cable, and satellite
Several technical matters affect data communications
One is bandwidth – bits-per-second (bps) transmission capability of a channel
Three types:
Voiceband – also known as low bandwidth; standard phone line; too slow for many types of transmissions – especially high-quality video; typical speeds are 56 to 96 kbps
Medium band – with special leased lines to connect minicomputers and mainframes as well as to transmit data over long distances (for larger computer systems); not typically used by individuals
Broadband – used for high-capacity transmissions (DSL, cable, satellite connections); specialized high-speed devices; effectively transmits high-quality video and other communication needs; typically 1.5 mbps; higher speeds possible
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17. Protocols Set of communication rules
Standard for Internet: TCP/IP (Transmission control protocol/Internet protocol)
Identification
Packetization
Rules for exchanging data between computers
Essential features of protocol
Identification - Identifying sending and receiving devices (IP address); (key term) Internet unique number address; domain name server (DNS) (key term) converts text-based addresses to IP addresses
Packetization – allows message to be broken into so easier to transmit over Internet through various interconnected networks; allows message to be reassembled at destination
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18. Networks A computer network is a communication system
Connects two or more computers
Allows information exchange
A computer network is a communication system that connects two or more computers so that they can exchange information and share resources
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19. Computer Networks Connect Computers
9-19
Computer Networks
Computer Networks Connect Computers
Common network terms
Node
Client
Server
Switch
Network interface cards (NIC)
Network operating system (NOS)
Distributed processing
Host computer
Network administrator
Node – any device connected to a network
Client – a node that requests and uses resources available from other nodes
Server – a node that shares resources with other nodes; dedicated servers specialize in performing specific tasks—could be an application server, communication server, database server, file server, printer server, or Web server
Switch – the center or central node for other nodes
Network interface cards (NIC) – connects the computer to a network
Network operating system (NOS) – software to control and coordinate activities between computers on a network
Distributed processing - computing power located and shared at different locations
Host computer – large centralized computer
Network administrator – a computer specialist; network administrator
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20. Network Types Local area networks Home networks WLAN
Metropolitan area networks
Wide area networks
LAN
Communications networks differ in geographical size. Three important types are:
1)LANs
Computers and devices linked in close proximity to each other
Linked by cable
Typically use a bus (key term) form of organization
With gateways, LANs can be connected to other LANs or any other type of network. Ethernet (key term) is one standard for connecting network nodes together.
Home Networks – LANs are now being commonly used by individuals in home/apartments; allow different computers to share resources including a common Internet connection; can be connected by various means including a wireless LAN (key term) (WLAN) that uses radio frequencies to connect computers; all communications pass through the network’s centrally located wireless receiver (key term) or base station (key term)
Home networking includes the following:
Radio frequency, telephone lines, electric wiring, cables, NIC/adapter cards
2)MANs (metropolitan area network)– also known as a regional network; (key term) span distances up to 100 miles
Network linking nodes and resources within the geographical bounds of a city
Cellular phones can extend the reach of a MAN
3)WANs (wide area networks)
Countrywide and worldwide networks
Use microwave relays and satellites to reach users
Internet is the widest WAN
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21. Network Architecture Topology describes how a network is arranged
Arrangement is called topology
Types of network topology
Star
Bus
Ring
Tree
Networks are connections of two or more computers that work together to exchange information and share resources
The network architecture describes how the network is arranged and how the resources are coordinated and shared
Network architecture also describes how a computer network is configured and what strategies are used
 Topology – network arrangement or configuration
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22. Star Network Smaller computers linked to a central unit
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Star Network
Smaller computers linked to a central unit
Central unit is called the network hub
Control is maintained by polling
Host computer – large centralized computer, usually a mainframe
Star network (Key Term) – nodes are connected to a single computer called a network hub
All communications pass through the hub/host computer; each connecting device is asked (“polled”) whether it has a message to send and then each device is in turn allowed to send its message
Can be used as a time-sharing system (key term)
Return
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23. Bus Network Each device handles its own communication control
9-23
Bus Network
Each device handles its own communication control
There is no host computer
Has a common connecting cable called a backbone
Bus network (key term)– each device handles its own communications control
No host computer
Common connecting cable called a bus or backbone
Not as efficient as star, but it is low cost and widely used
Return
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24. Ring Network Each device is connected to two other devices
9-24
Ring Network
Each device is connected to two other devices
No central file server or computer
Useful in a decentralized environment
Ring network (key term)
Each device connected to two others forming a ring
No central files server or computer
Messages passed around ring until reach correct destination
Often used to link mainframes—especially over wide geographical areas
Useful in decentralized organization
Makes possible distributed data processing system (key term)
Computers can perform processing tasks on own
Can also share programs, data, and other resources
Return
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25. Tree Network Several computers linked to a central host
9-25
Tree Network
Several computers linked to a central host
Computers are hosts to other computers
Useful in centralized organizations
Tree Network (key term)
Sometime called hybrid network
Consists of several computers linked to central host computer
All computers can server as hosts to other computers (unlike star network)
Host at top could be mainframe; computers below could be minis; then “down” to micros
Useful in centralized organization
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26. Principal Network Configurations
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27. Organizational Internets
9-27
Organizational Internets
Intranets
Private network within an organization
Provides information to employees
Extranets
Private network that connects organizations
Used to allow suppliers and others access
Firewalls
Security system
Protects against external threats
Intranet – Intranets use browsers, Web sites, and Web pages like the public Internet; typically include , mailing lists, newsgroups, and FTP services
Extranet – Purpose is to increase efficiency and reduce costs
Firewalls – Organizational firewalls include a proxy server (key term) that is a gatekeeper; all communications between the outside world and an organization must pass through the proxy server where the source and content of each communication is evaluated; end users have many of the same concerns regarding security as organizations and can use firewalls as well
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28. Careers In IT Network Administrator
9-28
Careers In IT
Network Administrator
Manage a company’s LAN and WAN networks
Maintain hardware and software
Diagnose and repair problems
Candidates usually have a bachelor’s degree in computer science and practical experience
Annual salary is typically between $48,500 and $79,000
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29. A Look to the Future Cars that Monitor and Respond
Pod car (Personalization on Demand)
Predicts and responds
Designed to learn and adapt to an individual's driving needs and habits
Toyota and Sony are collaborating on a "smart" car
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30. Discussion Questions (1 of 2)
Define and discuss connectivity, the wireless revolution, and communications.
Identify and describe the various physical and wireless communication channels.
Identify the standard Internet protocol and discuss its essential features.
Have students turn to the end of Chapter 9 in their textbooks to view the same “Open-Ended” questions/statements
Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

31. Discussion Questions (2 of 2)
Define and discuss the four principal network topologies.
Define and discuss three common network strategies.
Have students turn to the end of Chapter 9 in their textbooks to view the same “Open-Ended” questions/statements
Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.