1. Telecommunications & Networks Chapter 8

2. Telecom & NetworksIS for Management2 Chapter 8 Model User User Computer HW SW Connections InternetLANWAN Voice/Telephone Systems Network Operating System Network Management Security Administration

3. Telecom & NetworksIS for Management3 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

4. Telecom & NetworksIS for Management4 Information Superhighway More than the Internet ALL communications channels, no matter what the bandwidth/speed Used for all purposes

5. Telecom & NetworksIS for Management5 Telecommunications System Components Computers/terminals Communications channels (composed of communications media) Communications processors Communications software

6. Telecom & NetworksIS for Management6 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

7. Telecom & NetworksIS for Management7 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

8. Telecom & NetworksIS for Management8 Communications Channels #1 Means by which signal is transmitted from one device to another Can use different kinds of transmission media

9. Telecom & NetworksIS for Management9 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

10. Telecom & NetworksIS for Management10 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

11. Telecom & NetworksIS for Management11 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

12. Telecom & NetworksIS for Management12 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

13. Telecom & NetworksIS for Management13 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)

14. Telecom & NetworksIS for Management14 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

15. Telecom & NetworksIS for Management15 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

16. Telecom & NetworksIS for Management16 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 –Unified messaging systems combine voice, fax, & e-mail in one system

17. Telecom & NetworksIS for Management17 Network Services & Broadband VAN: Private, multipath, data-only, network managed by a 3 rd 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)

18. Telecom & NetworksIS for Management18 Telecommunications Technologies E-Mail Groupware Voice Mail Fax Teleconferencing –Data- –Video- Digital information services –AOL, Yahoo!, MSN, Lexis Distance education (synchronous or async.)

19. Telecom & NetworksIS for Management19 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

20. Telecom & NetworksIS for Management20 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)

21. Telecom & NetworksIS for Management21 Next Class Chapter 9: The Internet & The New IT Infrastructure Case Study: General Motors