WAN.ppt

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WAN.ppt

  1. 1. <ul><li>Wide Area Networks </li></ul>
  2. 2. Wide Area Network <ul><li>It connects computers and LANs over a larger geographical area. </li></ul><ul><li>It crosses public thorough-fares such as roads, railroads, and water. </li></ul>
  3. 3. WAN vs. LAN <ul><li>Geography </li></ul><ul><li>Ownership </li></ul><ul><li>Management </li></ul><ul><li>Speed </li></ul><ul><li>Cost </li></ul>
  4. 4. Wired Analog Service <ul><li>It uses standard wired analog telephone lines. </li></ul><ul><li>It requires a modem to convert digital signals to analog signals. </li></ul><ul><li>Its top is speed 56 Kbps. </li></ul><ul><li>Asymmetric – Some modems are faster downloading than uploading. </li></ul>
  5. 5. Wired Analog Service
  6. 6. Digital Cellular <ul><li>It provides WAN data access to mobile users. </li></ul><ul><li>Its coverage area is divided into smaller cells. </li></ul><ul><li>Users “roam” into adjacent cells or “handoff” into remote networks. </li></ul><ul><li>The current technology is 2.5G with a maximum speed of 384 Kbps. </li></ul>
  7. 7. Trunk-Based Leased Lines <ul><li>The same type of lines are used to connect the telephone company’s switches. </li></ul><ul><li>They provide “always-on” high-speed connections. </li></ul><ul><li>The most common is T1, which oper-ates at 1.5 Mbps over twisted pair wires. </li></ul>
  8. 8. Trunk-Based Leased Lines
  9. 9. Digital Subscriber Lines (DSL) <ul><li>They transmit at 1.5 Mbps over regular telephone lines. </li></ul><ul><li>They use the higher unused frequencies to send data. </li></ul><ul><li>Different versions of DSL: ADSL, G.list, HDSL, HDSL2 </li></ul>
  10. 10. Digital Subscriber Lines (DSL)
  11. 11. Cable Modem <ul><li>It uses the same coaxial cable that brings in cable TV signals. </li></ul><ul><li>All cables for a neighborhood are connected to a neighborhood splitter. </li></ul><ul><li>The connection is shared among all users in a neighborhood. </li></ul><ul><li>Speed: 300 Kbps – 1.5 Mbps </li></ul>
  12. 12. Local Multipoint Distribution Service (LMDS) <ul><li>Transmits: Maximum 155 Mbps downstream and 1.54 upstream </li></ul><ul><li>Range: 2 – 5 miles </li></ul><ul><li>It is a low-cost option to laying fiber optic cables. </li></ul><ul><li>Its signals are susceptible to interference from rain or fog. </li></ul>
  13. 13. Multichannel Multipoint Distribution Service (MMDS) <ul><li>It uses lower-frequency signals than LMDS. </li></ul><ul><li>Range: up to 35 miles </li></ul><ul><li>Its signals are less susceptible to interference from rain or fog. </li></ul>
  14. 14. Satellites <ul><li>They have been used for over 40 years. </li></ul><ul><li>They relay signals from one point on earth to another. </li></ul><ul><li>They are classified according to the type of orbit. </li></ul>
  15. 15. Low Earth Orbiting (LEO) <ul><li>They orbit at an altitude of 200 – 900 miles. </li></ul><ul><li>They circle the earth in 90 minutes. </li></ul><ul><li>They have a small “footprint.” </li></ul><ul><li>More satellites are needed to cover the entire earth. </li></ul>
  16. 16. Low Earth Orbiting (LEO)
  17. 17. Medium Earth Orbiting (MEO) <ul><li>They orbit at altitudes between 1,500 – 10,000 miles. </li></ul><ul><li>They circle the earth every 12 hours. </li></ul><ul><li>They have a large “footprint.” </li></ul><ul><li>Fewer are needed to cover the earth. </li></ul>
  18. 18. Remote Wireless Bridge <ul><li>It connects LANs located in different buildings. </li></ul><ul><li>The distance between buildings can be up to 18 miles at 11 Mbps. </li></ul><ul><li>It has similar characteristics to a wireless LAN. </li></ul>
  19. 19. Free Space Optics (FSO) <ul><li>It transmits up to 1.25 Gbps at a distance of 2.5 miles. </li></ul><ul><li>It uses low-powered infrared beams. </li></ul><ul><li>Its transmissions cannot be eavesdropped. </li></ul>
  20. 20. Virtual Private Network (VPN) <ul><li>It uses the public Internet to transmit private data. </li></ul><ul><li>It encrypts data into a packet before sending. </li></ul><ul><li>There is no cost for setting up or using a VPN. </li></ul>
  21. 21. Virtual Private Network (VPN)
  22. 22. Public Switched Data Networks (PSDN) <ul><li>Actual network itself </li></ul><ul><li>X.25 </li></ul><ul><li>Frame Relay </li></ul><ul><li>Asynchronous Transfer Mode (ATM) </li></ul>
  23. 23. Public Switched Data Networks (PSDN) <ul><li>Integrated Services Digital Network (ISDN) </li></ul><ul><li>Synchronous Optical Network (SONET) </li></ul><ul><li>Metro Ethernet Network (MEN) </li></ul>
  24. 24. Firewall <ul><li>It inspects incoming traffic. </li></ul><ul><li>Packet-filter firewall – Inspects header of each packet. </li></ul><ul><li>Stateful packet-filter firewall – Examines a packet’s source IP. </li></ul><ul><li>Proxy firewall – Examines the contents of a packet. </li></ul>
  25. 25. Network Address Translators (NAT) <ul><li>Disguises the internal IP by substituting a fake IP and port number. </li></ul><ul><li>When a packet is returned, NAT replaces the fake numbers with the actual IP and port number. </li></ul>
  26. 26. Privacy <ul><li>Privacy is the right to be left alone to the degree that you choose. </li></ul><ul><li>It is a difficult problem to keep personal data private. </li></ul><ul><li>Identity theft is a major crime. </li></ul>
  27. 27. Networking BASICS <ul><li>The Internet and Its Tools </li></ul>
  28. 28. The Internet <ul><li>It is not controlled or managed by one person or group. </li></ul><ul><li>Anyone can connect to the Internet. </li></ul><ul><li>There is no control regarding what can be posted. </li></ul>
  29. 29. History <ul><li>The U.S. was concerned that foreign nations may attack. </li></ul><ul><li>A computer network was needed that could withstand an attack. </li></ul><ul><li>The Internet was modeled after the interstate highway system. </li></ul>
  30. 30. History <ul><li>ARPANET was launched in 1969 to link 4 sites. </li></ul><ul><li>TCP/IP allowed multiple computers to connect to each other. </li></ul><ul><li>It was replaced by NSFNET in the 1980s. </li></ul><ul><li>Hypertext Transport Protocol and browsers opened up the Internet to anyone. </li></ul>
  31. 31. Domain Name System (DNS) <ul><li>It resolves (or finds) a Web site’s IP number when given its name. </li></ul><ul><li>It is a database organized as a hierarchy. </li></ul><ul><li>It is organized into 3 different levels. </li></ul><ul><li>DNS is distributed at multiple locations. </li></ul>
  32. 32. Domain Name System (DNS)
  33. 33. Web Browsers <ul><li>They allow users to view text, data, pictures, animation, and video. </li></ul><ul><li>A Web page contains instructions to a browser about how to display items. </li></ul><ul><li>Microsoft Internet Explorer is the most popular browser. </li></ul>
  34. 34. E-Mail <ul><li>It is the most common Internet tool. </li></ul><ul><li>They are either character-based or use a graphical user interface. </li></ul><ul><li>Documents are sent as attachments. </li></ul><ul><li>File compression software reduces the size of attachments. </li></ul>
  35. 35. Listserv <ul><li>It is also called a discussion list. </li></ul><ul><li>It is an extension of an e-mail distribution list. </li></ul><ul><li>Users subscribe and automatically receive copies of all e-mail messages. </li></ul><ul><li>Listserv address – Address of the automated mailing program. </li></ul>
  36. 36. Listserv Etiquette <ul><li>Spend time reading before responding. </li></ul><ul><li>Use a descriptive Subject heading. </li></ul><ul><li>Include part of the original message when replying. </li></ul><ul><li>Use upper- and lowercase. </li></ul>
  37. 37. Newsgroup <ul><li>Questions and answers are posted in a central location. </li></ul><ul><li>It is not necessary to save or sort e-mail messages. </li></ul><ul><li>It may require special software of the client. </li></ul>
  38. 38. Newsgroup
  39. 39. Portals <ul><li>Portals are also known as an online service. </li></ul><ul><li>Portals are ready-made menus of lists of information. </li></ul><ul><li>Each selection narrows choices until the information is located. </li></ul>
  40. 40. Search Engine <ul><li>The spider reads the Web pages and stores information in an index. </li></ul><ul><li>The search engine sifts through the index to find the user’s requests. </li></ul><ul><li>The ranking of pages is important. </li></ul>
  41. 41. Search Engine
  42. 42. Hypertext Markup Language (HTML) <ul><li>It is the standard way of defining how text and graphics are displayed. </li></ul><ul><li>The browser reads HTML document instructions. </li></ul>
  43. 43. Hypertext Markup Language (HTML) <ul><li>Each page is made up of elements. </li></ul><ul><li>The elements are indicated by tags. </li></ul><ul><li>A tag is <, tag name, >. </li></ul><ul><li>The ending tag contains a slash. </li></ul><ul><li><HTML> . . . </HTML> </li></ul>

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