2. Excellence Publication Co. Ltd. Volume 1 2.91 Volume 1

3. Excellence Publication Co. Ltd. Volume 1 2.92  Computer networking concerns with a collection of computers and peripherals that are interconnected through wireless technology. Definition of Computer Networking Tom, Thank you I’ve got it.

4. Excellence Publication Co. Ltd. Volume 1 2.93 (a) Hardware devices Computer Networking (c) Data (b) Software application Below items can be shared by different users in the network:

5. Excellence Publication Co. Ltd. Volume 1 2.94 A. Local Area Networks (LANs) 1. Definition of a LAN  a network of a personal computer or workstation that spans a relatively small physical area 2. Advantages of Using LANs  can transmit large amounts of data  can transmit data at very fast rate

6. Excellence Publication Co. Ltd. Volume 1 2.95 3. Disadvantages of Using LANs  The connection distance and the number of computers attached to a single LAN are limited. 4. Different Types of Topologies in a LAN Bus Topology Ring Topology Star Topology

7. Excellence Publication Co. Ltd. Volume 1 2.96 5. Transfer Protocols  the message transfer is managed by a transfer protocol such as the TCP/IP  TCP/IP enables the Internet to detect and correct transmission problems automatically  TCP/IP connection is primarily point-to-point 6. Controlling Software  the network operating system, such as NetWare, Unix, Linux or Microsoft Windows, that resides in the server

8. Excellence Publication Co. Ltd. Volume 1 2.97 7. Access Methods  the physical transfer of data is performed by an access method such as the Ethernet or Token Ring 8. Communications Paths  the telephone lines, coaxial cables, optical fibers and so on that connect the network adapters

9. Excellence Publication Co. Ltd. Volume 1 2.98 B. Wide Area Networks (WANs)  a network of LANs that spans a relatively large geographical area LAN WAN Network of personal computers or workstations that spans a relatively small physical area. Definition CoveredArea A single building or group of buildings. A city, a country or even the world. Network of LANs that spans a relatively large geographical area. A comparison of a LAN and a WAN

10. Excellence Publication Co. Ltd. Volume 1 2.99 A. Wire-based Communications Channels  communications channels that can be found all over the world 1. Telephone Lines Pairs of insulated copper wires Telephone line Twisted-pair wire A Twisted-pair cable

11. Excellence Publication Co. Ltd. Volume 1 2.910  In order to connect to the Internet through telephone lines, we have to use modems. Internal Modem External Modem Internal Modem External Modem Appearance Position Expansion board Inserted into vacant expansion slots. Attached to computers through the standard RS-232. Internal and External Modems

12. Excellence Publication Co. Ltd. Volume 1 2.911  used for cable television and computer network connections 2. Coaxial Cables Insulating material Central wire Plastic outer coating Woven or braided metal  more expensive than telephone lines, but can transmit much more data at a time

13. Excellence Publication Co. Ltd. Volume 1 2.912  used extensively by telephone companies to rebuild their communications infrastructure 3. Optical Fibers Data transmitted within an optical fiber Transmitted as light rays Signals

14. Excellence Publication Co. Ltd. Volume 1 2.913 Several fibers are bundled into a common sheath to form a fiber cable sheath to form a fiber cable Opaque plastic protective coating Transparent core Light-reflecting cladding layers Optical Fibers Layers of moisture barrier sheathing and impact-resistant plastic jackets Fiber Cable Optical Fiber

15. Excellence Publication Co. Ltd. Volume 1 2.914 Advantages of using optical fibers over telephone lines or coaxial cables (1) greater bandwidths  the transmission speed is faster (2) data can be transmitted digitally (3) not susceptible to electrical interference (4) much more difficult to tamper with (5) much thinner and lighter

16. Excellence Publication Co. Ltd. Volume 1 2.915 Disadvantages of using optical fibers over telephone lines or coaxial cables (1) more expensive to install (2) more easily damaged (3) more difficult to split

17. Excellence Publication Co. Ltd. Volume 1 2.916 B. Wireless Communications Channels 1. Analogue and Digital Signals from Land-based Antennas  used for cable television broadcast, inter- urban telephone traffic and so on Microwave antenna Signals carried by microwave

18. Excellence Publication Co. Ltd. Volume 1 2.917 Advantages of using land-based microwave antennas over telephone lines or coaxial cables (1) no need to install any cables (2) installation and maintenance costs of cables can be saved (3) communications mobility is higher

19. Excellence Publication Co. Ltd. Volume 1 2.918 2. Analogue and Digital Signals from Communications Satellites  used for global positioning, navigation and messaging services  in a circular orbit above the earth  more expensive than land-based microwave antennas  can view a stationary patch which covers more than one-third of the global

20. Excellence Publication Co. Ltd. Volume 1 2.919 3. Infrared Waves from Infrared Devices  used for short-distance remote controls  transmission and reception by invisible band of radiation

21. Excellence Publication Co. Ltd. Volume 1 2.920 4. Radio Waves from Bluetooth Devices  used for short-distance mobile communications  speed is up to 720Kbps data transfer within a range of 10 metres  use omnidirectional radio waves that can transmit through non-metal barriers

22. Excellence Publication Co. Ltd. Volume 1 2.921 State two kinds of wireless communication channels and compare their differences based on the following criteria: (a) way (b) speed (c) limitations

23. Excellence Publication Co. Ltd. Volume 1 2.922 Back