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Telecommunications & Networks

Telecommunications & Networks. Chapter 8. Voice/Telephone Systems. Internet. User Computer HW SW Connections. LAN. WAN. User. Chapter 8 Model. Network Operating System Network Management Security Administration. Convergence. Merging of technologies Applications

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Telecommunications & Networks

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  1. Telecommunications & Networks Chapter 8

  2. Voice/Telephone Systems Internet User ComputerHWSWConnections LAN WAN User Chapter 8 Model Network Operating SystemNetwork ManagementSecurityAdministration IS for Management

  3. Convergence • Merging of technologies • Applications • Edutainment (Bill Gates’ word for merging of education & entertainment, as in Typing Tutor) • MS Windows expanding to include browser, email, etc. • Hardware • Computers & communications formerly managed by two different departments in an organization; now usually managed by one department • Increasingly deregulated industries can now develop & produce in areas in which they were previously restricted • Any place/any time/any device concept means one device to do almost anything IS for Management

  4. Information Superhighway • More than the Internet • ALL communications channels, no matter what the bandwidth/speed • Used for all purposes IS for Management

  5. Telecommunications System Components • Computers/terminals • Communications channels (composed of communications media) • Communications processors • Communications software IS for Management

  6. Telecommunications System Functions • Transmits information • Establishes interface between sender & receiver • Routes messages along most efficient paths • Performs elementary processing to ensure message is received by right recipient • Edits message to ensure that message received is same as message sent • Converts messages for speed & format IS for Management

  7. Analog vs. Digital Signals • Analog • Continuous wave • Telephone, television, radio • Signal attenuates, losing strength over distance • Repeated or amplified signal may not be exactly the same as original signal • Digital • Discrete signal (not continuous): on/off • Electric light switch (not rheostat) • Signal attenuates less • When repeated or amplified, signal is restored to original pattern • Modem converts analog/digital signals IS for Management

  8. Communications Channels #1 • Means by which signal is transmitted from one device to another • Can use different kinds of transmission media IS for Management

  9. Communications Channels #2 • Wired • Twisted wire (twisted pair; untwisted pair) • Cheap, easy to install, slow • Coaxial cable (thick & thin) • Reasonable, harder to install, faster • Fibre optic cable (signal is light pulses, not electricity) • Expensive, hard to install, fastest • Originally backbone media, but now extended to buildings, homes, etc. • Optical networks use fibre optic cable • DWDM (dense multiwave division multiplexing) means more signal can be sent at one time: faster IS for Management

  10. Communications Channels #3 • Wireless • Uses electromagnetic spectrum (EMS) • Ranges of frequencies of EMS assigned for different functions • Microwave systems: line-of-sight, only 25-30 miles apart • Satellite systems: geosynchronous orbit (same concept as line-of-sight), high orbit (22,000 miles above earth) vs. low orbit (much closer, can receive weaker signals from cheaper microwave stations) • Paging systems, cellular telephones, personal communication services (PCS), personal digital assistants (PDA) • Mobile data networks IS for Management

  11. Speed • Bandwidth: Range of frequencies that can be accommodated on a particular channel; greater the range, greater the transmission capacity • Baud: Binary event representing signal change from positive to negative or vice versa; not the same as bit rate (bits per second – bps); bit rate generally higher than baud rate IS for Management

  12. Communications Processors & Software • Communication Processors • Front-end processor • Concentrator • Controller • Multiplexer (MUX) • Software to run all of these processors • Network, access, & transmission control • Error detection/correction • Security IS for Management

  13. Network Topologies #1 • Star • Central “hub” computer • All messages go through hub computer - centralization • If hub computer fails, network fails (single point of failure) • Tree (extended star) • Bus • Single circuit connects all computers • “Collisions” possible (depends on model) IS for Management

  14. Network Topologies #2 • Ring • Computers connected in a circle, data flow in only one direction • Failure of one computer may crash network (solution: ring-star) • Hybrid • Combination of more than one of the three network topologies IS for Management

  15. PBXs, LANs, & WANs #1 • PBX: Special purpose computer for handling telephone calls and data • Do not require special wiring (just telephone wiring) • Geographic scope limited • Cannot handle high volume data traffic • LAN: Network over a limited distance with dedicated channels • Server • Gateway/bridge/router • Network operating system (NOS) • Peer-to-peer or client/server IS for Management

  16. PBXs, LANs, & WANs #2 • WAN: Network over a larger distance that may use multiple, non-dedicated channels • Switched lines • Dedicated lines • Satellites, etc. • Converged networks • Deliver voice, data, video, etc. in a single network infrastructure • Unifiedmessaging systems combine voice, fax, & e-mail in one system IS for Management

  17. Network Services & Broadband • VAN: Private, multipath, data-only, network managed by a 3rd party that adds services, such as protocol conversion; cheaper than owning because costs are shared by subscribers • Packet switching (X.25) • Broadband technologies • Frame Relay • ATM (asynchronous transfer mode) • ISDN (Integrated Services Digital Network) • DSL (digital subscriber line) • Cable model • T1 line (T3) IS for Management

  18. Telecommunications Technologies • E-Mail • Groupware • Voice Mail • Fax • Teleconferencing • Data- • Video- • Digital information services • AOL, Yahoo!, MSN, Lexis • Distance education (synchronous or async.) IS for Management

  19. EDI Electronic data interchange: Transfer of standardized data between computers of different organizations • Lowers transaction costs • Reduces paperwork & errors • Can lock in customers & suppliers • Can minimize inventory & inventory costs • Previously used private networks but moving toward use of the Internet and XML IS for Management

  20. Case: Monitoring Employees on Networks • Is it ethical? Is there a yes or no answer to this question? If not, when is it ethical? When is it unethical? • Do you believe that zero tolerance for personal use of computers while at work is an appropriate policy? Why yes or why not? • ALWAYS ask what the policy is in your organization (including the U of M) IS for Management

  21. Next Class • Chapter 9: The Internet & The New IT Infrastructure • Case Study: General Motors IS for Management

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