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Transcript

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