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Communications and NetworksChapter 9 Communications and Networks
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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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. Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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. Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication Systems9-7 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication ChannelsChannels 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) Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication Channels SummaryCopyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Connection Device SignalsTypes 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Connection Device Types and Transfer SpeedsTypes 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Connection Service Dial-Up services Leased lines – T1, T2, T3 and T4Digital 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Typical User Connection Costs & SpeedsCopyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Bandwidth Measurement of the capacity of the channel CategoriesVoice 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Protocols Set of communication rulesStandard 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Networks A computer network is a communication systemConnects 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Computer Networks Connect Computers9-19 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Network Types Local area networks Home networks WLANMetropolitan 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Network Architecture Topology describes how a network is arrangedArrangement 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 This section, CONFIGURATIONS, is to be replaced by the attached file "Insert for page 255.docx.“ Could not find file. Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Star Network Smaller computers linked to a central unit9-22 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Bus Network Each device handles its own communication control9-23 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Ring Network Each device is connected to two other devices9-24 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Tree Network Several computers linked to a central host9-25 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Principal Network ConfigurationsCopyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Organizational Internets9-27 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
Careers In IT Network Administrator9-28 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
A Look to the Future Cars that Monitor and RespondPod 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
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.
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.
Networks & Components Discuss the components required for successful communications Explain the purpose of communications software Identify various sending.
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