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2. Danial Masood Chapter 11 Wide Area Network

3. Wide Area Network It connects computers and LANs over a larger geographical area. It crosses public thorough-fares such as roads, railroads, and water.

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. 4

5. Wired Analog Service 5

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. 6

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 operates at 1.5 Mbps over twisted pair wires. 7

8. Trunk-Based Leased Lines 8

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 9

10. 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 10

11. 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. 11

12. 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. 12

13. 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. 13

14. 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. 14

15. Low Earth Orbiting (LEO) 15

16. 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. 16

17. 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. 17

18. 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. 18

19. 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. 19

20. Virtual Private Network (VPN) 20

21. Public Switched Data Networks (PSDN) Actual network itself X.25 Frame Relay Asynchronous Transfer Mode (ATM) 21

22. Public Switched Data Networks (PSDN) Integrated Services Digital Network (ISDN) Synchronous Optical Network (SONET) Metro Ethernet Network (MEN) 22

23. 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. 23

24. 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. 24

25. 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. 25