chap006
TRANSCRIPT
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McGraw-Hill/Irwin Copyright © 2008, The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved.
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McGraw-Hill/Irwin Copyright © 2008, The McGraw-Hill Companies, Inc. All rights reserved.
Telecommunicationsand Networks
Telecommunicationsand Networks
Chapter
6Chapter
6
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• Understand the concept of a network
• Apply Metcalfe’s law in understanding the value of a network
• Identify major developments and trends in the industries, technologies, and business applications of telecommunications and Internet technologies
• Provide examples of the business value of Internet, intranet, and extranet applications
Learning ObjectivesLearning Objectives
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Learning ObjectivesLearning Objectives
• Identify the basic components, functions, and types of telecommunications networks used in business
• Explain the functions of major components of telecommunications network hardware, software, media, and services
• Explain the concept of client/server networking
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Learning ObjectivesLearning Objectives
• Understand the two forms of peer-to-peer networking
• Explain the difference between digital and analog signals
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Case 1: Wireless Mobile ApplicationsCase 1: Wireless Mobile Applications
• Best Buy’s Geek Squad remains connected via a Pocket PC phone• It connects wirelessly to Best Buy’s IT and
ordering system
• It also have Web browsing capabilities, for access to Google and Yahoo maps
• Handwriting recognition software bypasses small keyboard problem
• Voice recognition is being tested
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Case 1: Wireless Mobile ApplicationsCase 1: Wireless Mobile Applications
• Biggest problems• Lack of application software
• Reduced functionality of software that exists
• Requires middleware to synchronize data between back-end systems and the devices
• Applications don’t always meet worker’s needs
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Case Study QuestionsCase Study Questions
• What are the business advantages and limitations of the Best Buy Geek Squad’s use of their wireless Pocket PC mobile devices?• How have they overcome the limitations?
• What are the software development challenges of wireless mobile devices?• How are MedStar Health and Unifi meeting
those challenges?
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Case Study QuestionsCase Study Questions
• Why don’t the companies in this case use some of the thousands of software packages available for their wireless mobile devices?• What are the advantages and limitations of this
approach?
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Network ConceptsNetwork Concepts
• A network is an interconnected or interrelated chain, group, or system
• The number of possible connections on a network is N(N–1) or N2 –N• N = number of nodes (points of connection)• Example: 10 computers on a network = 10(10–1)
= 10x9 = 90 possible connections
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Metcalfe’s LawMetcalfe’s Law
• The usefulness, or utility, of a network equals the square of the number of users• The more users on a network, the more useful
it becomes
• Until critical mass is reached, a change in technology only affects the technology• Once critical mass is attained, social, political,
and economic systems change• Example: The Internet is growing exponentially.
We can expect more value, for less cost, virtually every time we log on.
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Telecommunication TrendsTelecommunication Trends
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Telecommunications-Based ServicesTelecommunications-Based Services
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Internet Networking TechnologiesInternet Networking Technologies
• Internet networking technologies are being used as technology platform• Web browser suites• HTML Web page editors• Network management software• Firewalls
• Being applied in Internet, intranet, and extranet applications
• Reinforces previous move toward client/server networks based on open-systems architecture
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Open SystemsOpen Systems
• Open systems use common standards for hardware, software, applications, and networks• Internet networking technologies are a common
standard for open systems
• Connectivity• Open systems provide greater connectivity
and network interoperability• Middleware may be needed to help diverse
systems work together
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MiddlewareMiddleware
• Middleware• A general term for any programming that
mediates between two separate programs• Allows a particular database to access other
databases without custom programming
• Commonly known as the “plumbing” of an information system • It routes data and information between back-end
data sources and end user applications• An essential component of any IT infrastructure
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Digital Network TechnologiesDigital Network Technologies
• Telecommunications are being revolutionized by switch from analog to digital• Analog: voice-oriented transmission• Digital: discrete pulse transmission
• Benefits• Higher transmission speeds• Moves larger amounts of information• Greater economy and much lower error rates• Transmits multiple types of communications
(data, voice, video) on the same circuits
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Wireless TechnologiesWireless Technologies
• Fiber-optic• Uses pulses of laser-generated light• Reduced size and installation effort• Vastly greater communication capacity• Faster transmission speeds• Freedom from electrical interference
• Satellite Transmission• Can move massive quantities of data, audio,
and video over global networks• Especially useful in isolated areas
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Business Application TrendsBusiness Application Trends
• Telecommunications networks now play a vital and pervasive role in Web-enabled…• E-business processes• Electronic commerce• Enterprise collaboration• Other applications that support operations,
management, and strategic objectives
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Internet2Internet2
• Next generation of the Internet• High-performance• Different infrastructure than the current Internet• Will not replace the current Internet• In use at over 200 universities, scientific
institutions, communications corporations• May never become totally open• Users are connected via Abilene, a backbone
that supports throughput of 10 Gbps• Infinite bandwidth
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Value of Telecommunications NetworksValue of Telecommunications Networks
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The Internet RevolutionThe Internet Revolution
• The Internet has become a global information superhighway• Millions of smaller, private networks operating
independent of, or in harmony with, each other• 10 servers in 1991 to over 46 million today• Sustained growth in excess of 1 million servers
per month• No central computer system• No governing body• Based on common standards
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Internet Service ProvidersInternet Service Providers
• ISP• A company that specializes in providing easy
access to the Internet• For a monthly fee, provides software, user name,
password, and Internet access
• ISPs themselves are connected to one another through network access points• One ISP can easily connect to another to obtain
addresses of websites or user nodes
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Internet ApplicationsInternet Applications
• Most popular Internet applications and uses• E-mail• Instant messaging• Browsing the Web• Newsgroups• Chat rooms• Publish opinions, subject matter, creative work• Buy and sell• Downloading (data, software, reports, pictures,
music, videos)
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Business Use of the InternetBusiness Use of the Internet
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Business Value of the InternetBusiness Value of the Internet
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The Role of IntranetsThe Role of Intranets
• Many companies have sophisticated and widespread intranets, offering…• Detailed data retrieval• Collaboration• Personalized customer profiles• Links to the Internet
• Intranets use Internet technologies• Web browsers and servers• TCP/IP network protocols• HTML publishing and databases
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IntranetsIntranets
• Intranets are protected by…• Passwords• Encryption• Firewalls
• Customers, suppliers, and other business partners can access an intranet via extranet links
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Business Value of IntranetsBusiness Value of Intranets
• Intranets support• Communications and collaboration
• Business operations and management
• Web publishing
• Intranet portal management
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Intranets as Information PortalsIntranets as Information Portals
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ExtranetsExtranets
• Network links that use Internet technologies to connect the intranet of a business to the intranets of another
• Virtual Private Networks• Direct private network links, or private secure
Internet links between companies
• Unsecured Extranet• Link between a company and others via the
Internet, relying on encryption of sensitive data and firewall security systems
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Extranet ConnectivityExtranet Connectivity
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Business Value of ExtranetsBusiness Value of Extranets
• Web browser technology makes customer and supplier access to intranets easier and faster
• Another way to build and strengthen strategic relationships
• Enables and improves collaboration between a business, customers, and partners
• Facilitates online, interactive product development and marketing
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Telecommunications Network AlternativesTelecommunications Network Alternatives
• Telecommunications is a highly technical, rapidly changing field• Most business professionals don’t need detailed
technical knowledge • However, understanding basic components and
their characteristics is necessary• Can help you make informed decisions about
telecommunications alternatives
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Case 2: Wireless Sensor NetworksCase 2: Wireless Sensor Networks
• HP experimenting with wireless networked sensors• Reinventing how companies manage the flow
of goods• Wireless sensor devices (motes) combine a circuit
board with networking and application software• Powered by a pair of AA batteries
• Mesh networking• Each device wakes for a fraction of a second to
transmit information to its nearest neighbor
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Case 2: Wireless Sensor NetworksCase 2: Wireless Sensor Networks
• Other uses• Ground-sensor networks can detect illegal
crossings of people or vehicles• Monitoring of industrial plants and ships• Remotely adjusting lighting and heat• Testing soil for pollutants• Detecting chemical storage leaks• Monitoring vibration levels• Analyzing traffic patterns
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Case Study QuestionsCase Study Questions
• What are some of the business benefits associated with using wireless networks to collect and transmit data?
• What are some of the challenges being faced in this use of wireless technologies?• What solutions can you offer?
• The use of wireless networking as described in the case is both innovative and functional. • What other business uses can you envision
for this approach?
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Telecommunications Network ModelTelecommunications Network Model
• A telecommunications network is any arrangement where• A sender transmits a message• To a receiver• Over a channel• Consisting of some sort of medium
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Telecommunications Network ModelTelecommunications Network Model
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Telecommunications Network ComponentsTelecommunications Network Components
• Terminals• Any input/output device that uses networks
to transmit or receive data
• Telecommunications processors• Devices that support data transmission, reception
• Telecommunications channels• Media over which data are transmitted, received
• Computers• All sizes and types
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Telecommunications Network ComponentsTelecommunications Network Components
• Telecommunications control software• Controls telecommunications activities• Manages the functions of telecommunications
networks
• Includes network management programs of all kinds• Telecommunications monitors (mainframes)• Network operating systems (network servers)• Web browsers (microcomputers)
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Network Component AlternativesNetwork Component Alternatives
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Types of Communications NetworksTypes of Communications Networks
• Primary types of communications networks• Wide Area • Local Area • Virtual Private • Client/Server• Peer-to-peer
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Wide Area Network (WAN)Wide Area Network (WAN)
• Telecommunication network that covers a large geographic area
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Local Area Network (LAN)Local Area Network (LAN)
• Connects computers within a limited physical area, such as an office, classroom, or building
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Virtual Private Networks (VPN)Virtual Private Networks (VPN)
• Used to establish secure intranets and extranets• The Internet is the main backbone network• Relies on network firewalls, encryption, and
other security features to build a “pipe” through the Internet
• Creates a private network without the high cost of a separate proprietary connection
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Virtual Private NetworkVirtual Private Network
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Client/Server NetworksClient/Server Networks
• Clients• End user personal computers or networked
computers
• Servers• Used to manage the networks
• Processing• Shared between the clients and servers• Sometimes called a two-tier architecture
• Larger computer systems are being replaced with multiple client/server networks
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Client/Server NetworkClient/Server Network
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Network ComputingNetwork Computing
• Networks are the central computing resource of the organization• Thin clients provide a browser-based user
interface for processing applets
• Thin clients include• Network computers• Net PCs• Other low-cost network devices or
information appliances
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Network ComputingNetwork Computing
• Application and database servers provide• The operating system• Application software• Applets• Databases• Database management software
• Sometimes called a three-tier client/server model because it consists of• Thin clients• Application servers• Database servers
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Network ComputingNetwork Computing
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Peer-to-Peer NetworksPeer-to-Peer Networks
• Central Server Architecture• P2P file-sharing software connects all PCs
to a central server• When a PC requests a file, the server searches
all active peers on the network• The server sends the requesting PC a list of
links to all active peers who have the file• Clicking a link connects the two PCs and
automatically transfers the file to the requesting PC
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Peer-to-Peer NetworksPeer-to-Peer Networks
• Pure Peer-to-Peer Architecture• No central directory or server• File-sharing software connects one PC to
another online user• When you request a file, the software searches
every online user and sends you a list of active file names
• Clicking a link automatically transfers the file from that user’s hard drive to yours
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Central Server Peer-to-Peer NetworksCentral Server Peer-to-Peer Networks
• Advantages• Can better protect the integrity and security
of the content and users of the network
• Disadvantages• Directory server can be slowed or overwhelmed
by too many users or technical problems
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Peer-to-Peer Network DiagramsPeer-to-Peer Network Diagrams
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Digital and Analog SignalsDigital and Analog Signals
• Analog or digital refers to the method used to convert information into an electrical signal• Analog: an electrical current is generated that
is proportional to the quantity being observed• Digital: the quantity being observed is expressed
as a number• Analog: if the temperature is 83 degrees, a measuring
device would generate 8.3 volts
• Digital: a measurement of 83 degrees would be displayed as the number 83
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Telecommunications MediaTelecommunications Media
• Twisted-Pair Wire• Ordinary telephone wire• Copper wire is twisted
into pairs
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Telecommunications MediaTelecommunications Media
• Coaxial Cable• Sturdy copper or
aluminum wire wrappedwith spacers to insulateand protect it
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Telecommunications MediaTelecommunications Media
• Fiber-Optic Cable• One or more hair-thin
filaments of glass fiber wrapped in a protective jacket
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The Problem of “The Last Mile”The Problem of “The Last Mile”
• Network providers use fiber optic cable as a communications backbone• Houses connected to the backbone are wired
with twisted pair• Users don’t benefit from the faster, better
technology
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Wireless TechnologiesWireless Technologies
• Terrestrial Microwave• Earthbound microwave systems transmit
high-speed radio signals• Follows a line-of-sight path between relay
systems spaced about 30 miles apart
• Communications Satellites• Serve as relay stations• Use microwave radio signals• Earth stations beam signals to the satellites• Not suitable for interactive, real-time processing
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Wireless TechnologiesWireless Technologies
• Cellular and PCS Telephone and Pager Systems• Geographic areas are divided into cells• Each cell has a low-power transmitter or radio
relay antenna• Computers and other communications processors
coordinate and control the transmissions to and from mobile users
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Wireless TechnologiesWireless Technologies
• Wireless LANS• Uses wireless radio-wave technology to
connect PCs within an office or a building• Can be high-frequency, similar to digital
cellular, or low frequency (spread spectrum)
• Bluetooth• Short-range wireless technology• Connects PCs to devices, such as a printer • Fairly low cost to implement
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Wireless TechnologiesWireless Technologies
• Other Wireless Systems• Cellular phones• Mobile radio• PDAs
• Telecommunications networks now play vital and pervasive roles in• Web-enabled e-business processes• Electronic commerce• Enterprise collaboration• Other applications that support business
operations, management, and strategic objectives
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The Wireless WebThe Wireless Web
• Wireless Internet access is growing as Web-enabled information appliances proliferate• Smart telephones, pagers, PDAs• All are very thin clients in wireless networks
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Telecommunications ProcessorsTelecommunications Processors
• Modems• The most common type of communications
processor• Converts a digital signal to an analog frequency
that can be transmitted over phone lines, then back into a digital signal
• Modulation and demodulation
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Comparing TechnologiesComparing Technologies
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Inter-Network ProcessorsInter-Network Processors
• Switch… makes connections between telecommunications circuits in a network
• Router… intelligent communications processor that interconnects networks based on different protocols
• Hub… a port-switching communications processor
• Gateway… connects networks with different communications architectures
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Communications ProcessorsCommunications Processors
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Communications ProcessorsCommunications Processors
• Multiplexer… allows a single communications channel to carry simultaneous data transmissions from many terminals• In time division multiplexing (TDM), the
multiplexer divides the time each terminal can use the high-speed into short time slots
• Multiplexers increase the number of transmissions possible
• Does not increase the number of physical data channels
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Telecommunications SoftwareTelecommunications Software
• May reside in PCs, servers, mainframes, and communications processors• Vital part of all telecommunications networks• Used to manage network performance• WANs often use telecommunications monitors
or teleprocessing monitors• Other networks use operating system software• Middleware helps diverse networks
communicate with each other
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Network Management FunctionsNetwork Management Functions
• Traffic Management• Manage network resources and traffic to
avoid congestion and optimize service levels
• Security• Provide authentication, encryption, firewall,
auditing, and enforcement
• Network Monitoring• Troubleshoot and watch over the network,
alerting administrators of potential problems
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Network Management FunctionsNetwork Management Functions
• Capacity Planning• Survey network resources, traffic patterns, and
users’ needs• Determine the best way to accommodate the
needs of the network as it grows and changes
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Network TopologiesNetwork Topologies
• Topology• The structure of a network
• Star Network• Ties end user computers to a central computer
• Ring Network• Ties local computer processors together in a ring
on a relatively equal basis
• Bus Network• Local processors share the same communications
channel
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Network TopologiesNetwork Topologies
• Mesh Network• Uses direct communications lines to connect
some or all of the computers in the ring to each other
• Switch• A message-switching computer that handles
data communication between autonomous local computers
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Network TopologiesNetwork Topologies
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Network Architectures and ProtocolsNetwork Architectures and Protocols
• Protocol• A standard set of rules and procedures for the
control of communications in a network
• Handshaking• The process of exchanging predetermined
signals and characters• Establishes a telecommunications session
between terminals and computers
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Network Architectures and ProtocolsNetwork Architectures and Protocols
• Network Architecture• Master plan of standard protocols, hardware,
software, and interfaces between end users and computer systems
• Goal is to promote an open, simple, flexible, and efficient telecommunications environment
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OSI and TCP/IP ModelsOSI and TCP/IP Models
• Open Systems Interconnection (OSI) Model• A seven-layer model that serves as a standard
model for network architectures• Model for how messages should be transmitted
between two points in a network• Each layer adds functions
• Transmission Control Protocol/Internet Protocol (TCP/IP)• A five-layer telecommunications protocol used
by the Internet
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OSI and TCP/IP ModelsOSI and TCP/IP Models
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Voice Over IPVoice Over IP
• Internet Telephony• Using an Internet connection to pass voice
data using IP instead of a telephone network• Often referred to as voice over IP or VoIP• Works like a regular phone, but skips long-
distance charges• Runs over standard network infrastructure• Requires a well-configured network to work
smoothly
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BandwidthBandwidth
• Bandwidth• The frequency range of a telecommunications
channel that determines the maximum transmission rate
• Speed and capacity typically measured in bits per second (bps)
• Sometimes call baud rate
• Transmission Rates• Narrow-band = low speed• Broadband = high speed
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Transmission SpeedsTransmission Speeds
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Switching AlternativesSwitching Alternatives
• Circuit Switching• Switch opens a circuit to establish a link
between a sender and a receiver• It remains open until the communication
session is completed
• Packet Switching• Breaks messages into groups called packets• Transmits packets separately
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Network InteroperabilityNetwork Interoperability
• Ensures that anyone anywhere on one network can communicate with anyone anywhere on another network• From a telecommunications perspective, no
need to speak a common language
• Telecommunications would be possible without• Complete accessibility• Transparency• Seamless interoperability across all networks
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Case 3: Leading the Way for VoIPCase 3: Leading the Way for VoIP
• VoIP works by• Digitizing a voice signal• Chopping it into packets• Sending them over a network or the Internet• Reassembling them at the destination
• VoIP allowed the Minnesota Dept. of Labor to cut its phone bill in half
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Case Study QuestionsCase Study Questions
• What are the main benefits that can be gained by companies that switch to VoIP systems?
• What are some of the major cost factors that may limit a positive rate of return from investments in VoIP projects?
• Should more companies switch to VoIP systems?
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Case 4: Serving Citizens with WirelessCase 4: Serving Citizens with Wireless
• Earth Alert Emergency Management System in Maryland provides• Devices to communicate warnings to individuals
before a disaster• Tools to collect timely information after a disaster
• Aurora, Colorado• Connects police and fire department vehicles
via wireless connections
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Case Study QuestionsCase Study Questions
• What is the business value of advanced mobile technologies in Maryland’s emergency management services?
• In what other government services could GPS serve to provide business value?
• As there disadvantages or risks associated with the deployment of GPS systems to monitor the location of people?