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  1. 1. Chapter 8 Communications and Networks
  2. 2. Communications <ul><ul><li>Process in which two or more computers or devices transfer data, instructions, and information </li></ul></ul>set-top boxes mainframe computers smart phones notebook computers servers Web-enabled PDAs desktop computers Tablet PCs GPS receivers
  3. 3. Successful Communications—5 components Sending device — initiates instruction to transmit data, instructions, or information Communications device — connects the communications channel to the receiving device Receiving device — accepts transmission of data, instructions, or information Communications device — connects the sending device to the communications channel Communications channel — media on which data, instructions, or information travel
  4. 4. Types of Networks <ul><ul><li>Collection of computers and devices connected via communications devices and transmission media </li></ul></ul><ul><ul><li>Local Area Network (LAN) </li></ul></ul><ul><ul><ul><li>Network in limited geographical area—office building </li></ul></ul></ul><ul><ul><li>Metropolitan area network (MAN)—covers city </li></ul></ul><ul><ul><li>Wide area network (WAN) </li></ul></ul><ul><ul><ul><li>Potentially world-wide coverage </li></ul></ul></ul><ul><ul><ul><li>Internet is the largest WAN </li></ul></ul></ul>
  5. 5. Types of Networks <ul><li>Client/Server </li></ul><ul><li>Peer to Peer </li></ul><ul><li>Simple network that connects fewer than 10 computers </li></ul><ul><li>Each computer has equal capabilities </li></ul><ul><ul><li>One or more computers act as server and other computers, or clients , access server </li></ul></ul>
  6. 6. Types of Networks <ul><li>What is Internet peer-to-peer ( P2P )? </li></ul><ul><li>Intranet </li></ul><ul><li>Restricted network usually within an organization </li></ul><ul><li>Allows sharing of organizational-related info without putting it out for public reading </li></ul>p. 292 Fig. 8-11 <ul><ul><li>Enables users to connect to each other’s hard disks and exchange files directly </li></ul></ul>Next
  7. 7. Networks Topology <ul><li>Layout of devices in a network </li></ul><ul><ul><li>Bus network </li></ul></ul><ul><ul><ul><li>All computers and devices connect to a central cable, or bus </li></ul></ul></ul><ul><li>Ring network </li></ul><ul><ul><li>Cable forms closed ring, or loop, with all computers and devices arranged along ring </li></ul></ul>
  8. 8. Networks Topology <ul><li>Star network </li></ul>p. 293 Fig. 8-14 <ul><ul><li>All devices connect to a central device, called hub </li></ul></ul><ul><ul><li>All data transferred from one computer to another passes through hub </li></ul></ul>Next
  9. 9. Ethernet and Token Ring Technology <ul><li>Ethernet technology allows computers to contend for access to network </li></ul><ul><ul><li>If two computers send data at same time, a collision occurs and computers must send again </li></ul></ul>Token ring technology controls access to network by requiring devices to pass a special signal, called token
  10. 10. Networks <ul><li>TCP/IP and 802.11 </li></ul><ul><li>BlueTooth </li></ul><ul><li>Short-range radio waves transmit data between Bluetooth devices </li></ul>p. 294 <ul><ul><li>TCP/IP ( T ransmission C ontrol P rotocol/ I nternet P rotocol) technology transmits data by breaking it up into small pieces, or packets </li></ul></ul><ul><ul><ul><li>Commonly used for Internet transmissions </li></ul></ul></ul><ul><ul><li>802.11 is family of standards for wireless LANs </li></ul></ul>Next
  11. 11. Networks <ul><li>What are IrDA , RFID , and Wireless Applications Protocol (WAP) ? </li></ul>p. 294 IrDA specification allows data to be transferred wirelessly via infrared light waves Wireless Applications Protocol (WAP) allow wireless mobile devices to access Internet Radio Frequency Identification (RFID) uses radio signals to communicate with a tag placed in an object
  12. 12. Communications Devices <ul><li>What are examples of communications devices ? </li></ul>p. 298 Next Common types are dial-up modems, ISDN and DSL modems, cable modems, network cards, wireless access points, and routers ISDN and DSL modems send and receive data from ISDN and DSL lines
  13. 13. Using the Telephone System to Communicate <ul><li>Public switched telephone network (PSTN)? </li></ul><ul><li>Dial-up line </li></ul><ul><ul><li>Temporary connection using telephone line for communications </li></ul></ul><ul><ul><ul><li>Costs no more than making regular call </li></ul></ul></ul><ul><ul><ul><li>Computers at any two locations can establish a connection using modems and telephone network </li></ul></ul></ul>
  14. 14. Communications Devices <ul><li>What is a cable modem ? </li></ul>p. 300 Fig. 8-19 <ul><ul><li>Sends and receives data over cable television network </li></ul></ul><ul><ul><li>Much faster than dial-up modem or ISDN </li></ul></ul><ul><ul><li>Sometimes called a broadband modem </li></ul></ul>Next
  15. 15. Communications Devices <ul><li>What is a network card ? </li></ul>p. 300 Fig. 8-20 <ul><ul><li>Adapter card, PC Card, or compact flash card that enables computer or device to access network </li></ul></ul>Next
  16. 16. Communications Devices <ul><li>What are ISDN and DSL modems ? </li></ul>p. 300 Communications devices that send and receive digital ISDN and DSL signals Usually external devices in which one end connects to a telephone line and the other end connects to a port on the system unit Next
  17. 17. Communications Devices <ul><li>What is a wireless access point ? </li></ul>p. 301 Fig. 8-21 <ul><ul><li>Central communications device that allows computers and devices to transfer data wirelessly among themselves or to wired network </li></ul></ul>Next
  18. 18. Communications Devices <ul><li>What is a router ? </li></ul><ul><ul><li>Connects computers and transmits data to correct destination on network </li></ul></ul><ul><ul><li>Routers forward data on Internet using fastest available path </li></ul></ul><ul><ul><li>Allow messages to flow between networks </li></ul></ul>
  19. 19. Firewalls <ul><li>Program or hardware device that filters information coming from Internet connection </li></ul><ul><li>If packet of info is flagged, not allowed through </li></ul>
  20. 20. Communications Channel <ul><li>What is a channel ? </li></ul>p. 303 <ul><ul><li>Transmission media on which data travels in communications system </li></ul></ul><ul><ul><li>Wire, cable, and other tangible materials used to send communications signals </li></ul></ul><ul><ul><li>Bandwidth is amount of data that can travel over channel </li></ul></ul><ul><ul><li>Transmission media are materials capable of carrying one or more signals </li></ul></ul>Next
  21. 21. Communications Channel <ul><li>How is a request sent over the Internet using a communications channel? </li></ul>p. 304 Fig. 8-24 Step 1. The sending device requests information using either a physical transmission media or a wireless transmission media. Step 2. When the request leaves the ISP, it travels over T1 lines, microwave stations, earth-based stations, and communications satellites until it reaches the Internet backbone. Step 3. The request travels over T3 lines along the Internet backbone. Step 4. The Request travels over T1 lines until it reaches the destination network server. Next
  22. 22. Physical Transmission Media <ul><li>What are twisted-pair cable and coaxial cable ? </li></ul>p. 305 Fig. 8-25—8-26 <ul><ul><li>Twisted-pair cable is used for telephone systems and network cabling </li></ul></ul><ul><ul><li>Coaxial cable is often used for cable television wiring </li></ul></ul>Next
  23. 23. Physical Transmission Media <ul><li>What is fiber-optic cable ? </li></ul>p. 306 Fig. 8-27 <ul><ul><li>Capable of carrying significantly more data at faster speeds than wire cables </li></ul></ul><ul><ul><li>Less susceptible to interference (noise) and, therefore, more secure </li></ul></ul><ul><ul><li>Smaller size (thinner and lighter) </li></ul></ul>Next
  24. 24. Wireless Transmission Media <ul><li>What is wireless transmission media ? </li></ul>p. 306 <ul><ul><li>Used when inconvenient, impractical, or impossible to install cables </li></ul></ul><ul><ul><li>Includes infrared, broadcast radio, cellular radio, microwaves, and communications satellites </li></ul></ul>Next
  25. 25. Internet Telephony p. 285 Next Internet telephony transmission of phone calls over data network Sometimes called Voice over IP
  26. 26. Uses of Computer Communications <ul><li>What are voice mail and wireless messaging services ? </li></ul>p. 289 Fig. 8-7 <ul><ul><li>Voice mail is voice message converted to digital form </li></ul></ul><ul><ul><li>Wireless messaging services include: </li></ul></ul><ul><ul><ul><li>Text Messaging </li></ul></ul></ul><ul><ul><ul><li>Instant Messaging </li></ul></ul></ul><ul><ul><ul><li>Picture Messaging </li></ul></ul></ul>Next
  27. 27. Collaboration and Groupware <ul><li>What are collaboration and groupware ? </li></ul><ul><ul><ul><li>Microsoft Office 2003 allows collaboration </li></ul></ul></ul><ul><ul><li>Groupware is software that allows people to share information </li></ul></ul><ul><ul><li>Collaboration is working with other users connected to a server </li></ul></ul>Next
  28. 28. Public Access Points <ul><ul><li>Public Internet access point allows wireless connection to Internet in public location </li></ul></ul><ul><ul><li>Hot spot </li></ul></ul>Next
  29. 29. Global Positioning System Next
  30. 30. Verichip (December, 2001) <ul><li>Implantable Personal Verification System </li></ul><ul><li>Uses RFID </li></ul><ul><ul><li>Size of a TicTac </li></ul></ul><ul><ul><li>Implanted under the skin </li></ul></ul><ul><ul><li>Immediate ID and retrieval of subscriber supplied registry info </li></ul></ul>