Wide Area Networks

1. Wide Area Networks Networking BASICS

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. Networking BASICS

3. WAN vs. LAN • Geography • Ownership • Management • Speed • Cost Networking BASICS

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. Networking BASICS

5. Wired Analog Service Networking BASICS

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. Networking BASICS

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. Networking BASICS

8. Trunk-Based Leased Lines Networking BASICS

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 Networking BASICS

10. Digital Subscriber Lines (DSL) Networking BASICS

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 Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

16. Low Earth Orbiting (LEO) Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

21. Virtual Private Network (VPN) Networking BASICS

22. Public Switched Data Networks (PSDN) • Actual network itself • X.25 • Frame Relay • Asynchronous Transfer Mode (ATM) Networking BASICS

23. Public Switched Data Networks (PSDN) • Integrated Services Digital Network (ISDN) • Synchronous Optical Network (SONET) • Metro Ethernet Network (MEN) Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

27. Networking BASICS The Internet and Its Tools Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

32. Domain Name System (DNS) Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

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. Networking BASICS

38. Newsgroup Networking BASICS

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. Networking BASICS

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. Networking BASICS

41. Search Engine Networking BASICS

42. Hypertext Markup Language (HTML) • It is the standard way of defining how text and graphics are displayed. • The browser reads HTML document instructions. Networking BASICS

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> Networking BASICS