Networking and Telecomunications


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Networking and Telecomunications

  1. 1. Networking & Telecommunications Introduction to Computer Science 2007-2008
  2. 2. Aims • Describe tech. that make telecomm. possible • Describe the nature and function of LANs and WANs • Discuss the use of online communication • Explain how wireless tech. is transforming how people work and comunicate • Describe trends in telecomm. and networking 4626. Introd to Computer Science
  3. 3. Contents 1. Basic Network Anatomy 2. Communication Software 3. E-mail and Instant Messaging 4626. Introd to Computer Science
  4. 4. Basic Network Anatomy • Hardware: share resources → reduce costs, powerful equipment • Software: share data → increases efficiency • People: enable people to work together and collaborate (CSCW) 4626. Introd to Computer Science
  5. 5. Networks Near and Far Local Area Netwok (LAN) • nodes: computers and peripherals • cable or wireless connections • different operative systems Metropolitan Area Netwok (MAN) • provided by telecomm. companies Wide Area Netwok (WAN) • nodes are networks • different media (telephonic lines, microwave, satellites) • bridges, gateways and routers connect networks 4626. Introd to Computer Science
  6. 6. Node: Backbone: any network peripheral high capacity lines Some interesting terms Hub: Switch: connects devices to a connects devices to a network (broadband) network (isolates) Router: Gateway: interconnect network protocol converter fragments
  7. 7. Specialised Networks GPS (Global Positioning System) • 24 sat. arounf Earth, 4 always over horizon • civil and military use Global Financial Systems • paper replaced by digital patterns as money • ATM (automatic teller machine) • e-commerce 4626. Introd to Computer Science
  8. 8. The Network Interface Direct connection • connects a device directly to the net • computer ports (serial, USB, Infrared) • Network Interface Cards (NIC) e.g. Ethernet 4626. Introd to Computer Science
  9. 9. The Network Interface Remote connection • modem or broadband connection device • Telephonic or TV networks to cover long distances • e-commerce 4626. Introd to Computer Science
  10. 10. Communication with Modem • Modulator/demodulator (analog/digital) • Internal or external (using serial/USB ports) • Modem fax to communicate with facsimile (fax) machines • Speed: • bits per second (bps): between 28,000 bps and 56,600 bps (56Kbits) • baud rate (symbols per second) 4626. Introd to Computer Science
  11. 11. Broadband Connection Bandwidth: quantity of inform. that can be transmitted Broadband connection: connection that use greater bandwidth • DSL (digital subscriber line) over phone lines • cable-modem over cable TV networks • high-speed wireless connections • satellite dishes 4626. Introd to Computer Science
  12. 12. Fiber-optic and Other Media Type Uses Distance Cost twisted pair small LANs 100 m. low coaxial cable big LANs 200 a 500 m. medium Backbones fiber-optic 2 a 100 km. high WANs infrared LANs 1 a 300 m. medium wireless (radio) Mobile devices variable high 4626. Introd to Computer Science
  13. 13. Wireless Technology Infrared • infrared tech. (as remote controls for TV) • short distances Bluetooth (about 1m.) • Radio tech. Wireless (WiFi) • create personal area networks • Radio tech. (PAN) • • standards: 802.11 a/b/g/n device oriented • • 50m. from base station distance up to 10. 4626. Introd to Computer Science
  14. 14. Communication Software Protocols • Rules for exchange data • Hardware must follow them • Network Operative Systems Network models • client/server • peer to peer (P2P) Terminal and emulation software 4626. Introd to Computer Science
  15. 15. The Network Advantage Share hw resources • reduce costs • more powerful devices Share data and programs • file servers to keep data and applications • P2P models in small networks • site and network licenses (economical) Groupware • support groups working together 4626. Introd to Computer Science
  16. 16. The Many Faces of E-mail • sent & receive messages from the network • stored on a server until user reads them • web-mail: accessing using a web browser • files as attachments • HTML or plain ASCII text emails 4626. Introd to Computer Science
  17. 17. Services Based on E-mail Mailing lists • participate on discussion groups • messages arrive to your mail box • subscription needed to participate Newsgroups • public discussion groups (without registration) • messages stored on a “notice board” 4626. Introd to Computer Science
  18. 18. Instant Messaging • text-based in early ages of internet (talk) • graphic interfaces nowadays • chat rooms (public) • bidirectional video conferences • variety of software and services • MS Messenger • Jabber (open source) • Pidgin (multiprotocol) 4626. Introd to Computer Science
  19. 19. Computer Telephony • Integrates telephonic services and computers • Examples • voice email • voice IP (VoIP) • Current trends: integration in one device 4626. Introd to Computer Science
  20. 20. Advantages of Online Communication • e-mail is fast • e-mail doesn’t depend on location • e-mail facilitates group communication • e-mail is digital data that can be combined with other computer generated documents • online comm. is less intrusive than telephone • online comm. allows time shifting • online comm. enables decisions to evolve over time • online comm. makes possible long-distance meetings • e-mail and instant messaging emphasize message over messenger 4626. Introd to Computer Science
  21. 21. click to see the skeetch Origin of the term ‘spam’ 4626. Introd to Computer Science