Elementary Computing CSC 100. M. Cheng, Computer Science

Transcription

1 Elementary Computing CSC 100 1

2 Networking History of Voice and Data Networks Dialup Modem and ADSL Ethernet and Local Area Network Network Speed Wired and Wireless Routers Eavesdropping and Network Security Mobile Telephone and Data Networks 2

3 Outcomes Networking is an essential service for computers and mobile devices. Most homes and offices are equipped with a Local Area Network. LANs are connected through gateways or routers to form a Wide Area Network. Mobile phone data networks are independent of our traditional Internet. 3

4 Study Guide What is a dialup or ADSL modem? What is a router or a hub? What is a LAN? What is a WAN? What is Ethernet? What is a wired or wireless router? How are IP addresses assigned by a router? 4

5 Study Guide How network speed is measured? What is SSID? What is packet sniffing? What is a rogue router? What is a firewall? How is mobile data network connected to the Internet? What is roaming & 4G mobile data network? 5

6 History of Telephones & Networks 6

7 Telephone Networks Telephone networks are older than the Internet by at least 60 years. Public Switched Telephone Network (PSTN) is a global network of regional telephone networks. They are designed primarily for voice communication. 7

8 The Internet The Internet was created in the 70 s as an experimental data network connecting up to 15 sites across the US, known as the ARPANET. Initially, connections were made over existing telephone networks. 8

9 How do we send data (1 s and 0 s) over a voice only network? 9

10 Dial- up Modems 10

11 A dialup modem is an equipment that converts 1s and 0s to audible sound, and vice versa. 11

12 Dialup Data/Fax Modem 12

13 Sound of a Dial- up Modem 13

14 A fax machine sends/receives a scanned document (in 1s and 0s) over the telephone using an internal dialup modem. 14

15 A Poor Man Machine 15

16 Sending Fax in Windows 16

17 Sending Fax in OS X 17

18 As the demand for faster speed increases, dialup modems are replaced by ADSL modems. 18

19 Asymmetric Digital Subscriber Line 19

20 Local Area Network (LAN) 20

21 LAN and Ethernet In 1974, XEROX research lab developed a personal office system called Alto. This system includes a GUI, a mouse, a laser printer and a Local Area Network (LAN) called Ethernet. This LAN connects several local computers to share printers and files. 21

22 Ethernet Port and Cable Ethernet Cable (8 pins) Ethernet Port 22

23 Ethernet Port and Cable Ethernet Cable (8 pins) Ethernet Port Telephone Modem Port Telephone Cable (4 pins) 23

24 A LAN is designed to work within an office or a building, typically under 100 meters. 24

25 How do you connect offices across blocks, streets, or towns? 25

26 Router 26

27 A Telephone Switch Board M. Cheng, Computer Science 27

28 What is a Router? It is an electronic switch board for computer communication. It allows data to be sent from one computer to another, and back. It has a Wide Area Network (WAN) connection to outside computers or networks. 28

29 What is a Router for? Several local computers can share a printer or files (e.g., documents, music, videos). A router has multiple LAN ports, one for each locally connected computer. It connects to the Internet via a WAN port; all local computers shared this WAN connection. 29

30 The Router Ports LAN ports (for local Computers and Printers) 30

31 The Router Ports WAN port (for ADSL modem and access to the Internet) LAN ports (for local Computers and Printers) 31

32 A Home Local Area Network WAN connection A Router or Gateway 32

33 A Home Local Area Network An ADSL modem connected to local Telephone or Cable network 33

34 Today, wireless LAN (or WiFi) is commonly used in offices and homes. 34

35 A WiFi Router LAN Ports 35

36 A WiFi Router WAN Port LAN Ports 36

37 Typical WiFi Router Setup 37

38 Router and IP Addresses Every connected computer or device is assigned a locally unique IP address. The WAN connection is assigned an external IP address by your Internet Service Provider (ISP). All connected devices will share this same external IP address when accessing the Internet. 38

39 Router s IP Address Assignment WiFi Router (When a router is connected to the Internet, it will have an IP address for its WAN port.) 39

40 Router s IP Address Assignment WiFi Router (When a computer is connected M. to Cheng, the router, Computer Science it will be assigned an IP address.) 40

41 Router s IP Address Assignment (When a laptop is connected to the WiFi router, it will be assigned an IP address.) WiFi Router

42 Router s IP Address Assignment (When a tablet is connected to the WiFi router, it will get an IP address.) WiFi Router

43 Router s IP Address Assignment (When a smartphone is connected to the WiFi router, it will also get an IP address.) WiFi Router

44 OS X Network Setup My machine s IP Address My router s IP address 44

45 Windows Network Setup My machine s IP Address My router s IP address 45

46 WiFi Router A typical wireless (also known as ) router has a range from 20 to 50 meters. A router will provide a dynamic IP address for each connected computer. Every WiFi router typically has a Service Set Identification (SSID) (e.g., UVic, UVicOpen). 46

47 Wide Area Network (WAN) 47

48 A WAN is designed to work across buildings and cities. 48

49 The Router Ports WAN port (for ADSL modem and access to the Internet) LAN ports (for local Computers and Printers) 49

50 A Home Local Area Network The Internet is a WAN An ADSL modem connected to local Telephone network A Router 50

51 LAN vs WAN LAN is typically used within an office, a home, or a building. WAN is typically used across buildings, cities, towns, states, provinces, and countries. A WAN connects many LANs (or other WANs) together to form a larger WAN. 51

52 Wide Area Network 52

53 Router and Network Security 53

54 What is a Firewall? It is a service which monitors all incoming and outgoing network traffic. It can block/allow certain network services, e.g., FTP, Skype, HTTP, etc. It prevents undesirable external network access by filtering certain IP packets. 54

55 OS X Firewall Setup 55

56 Windows 7 Firewall Setup 56

57 Packet Sniffing & Eavesdropping Any computer within the range of a wireless router can sniff all IP packets transmitted over the air. By collecting many IP packets, an intruder can determine what is being transmitted, e.g., names and passwords. 57

58 Security & Encryption Many WiFi routers provide a default security option (e.g., WEP, WPA, WPA2). A computer must provide a login password in order to obtain an IP address. All packets transmitted between a connected computer and the router are then encrypted. 58

59 OS X WiFi Security Setting 59

60 Windows WiFi Security Setting 60

61 Rouge Router & Fake SSID Any computer with a WiFi connection can be set up as a rouge router. An unsuspected user can be tricked to connect to a router with a fake SSID. As a result, all packets transmitted will be collected for analysis. 61

62 Mobile Telephone & Data Networks 62

63 First Mobile (Cellular) Telephone $4000 The Brick 63

64 Cellular Networks Public Switched Telephone Network 64

65 Mobile Phone Generations 1G mobile phones can only support voice over CDMA networks. 2G mobile phones support voice and SMS (Short Message Services up 160 chars) over GSM networks. 3G mobile phones support voice and high speed data access over GSM and CDMA networks. 65

66 A link between Mobile Network and the Internet 66

67 Mobile Data Networks Mobile Data Networks are proprietary networks supported by different mobile phone operators. Their services are not free! They charge every minute of phone calls or every byte of data transmitted. Mobile phones use phone numbers for identification; while the Internet uses IP addresses. 67

68 Roaming It is the ability for a mobile device to move within a mobile telephone network without losing its connection or identity. There is no such thing as mobile IP addresses!!! (Your IP address changes whenever you move.) Mobile phone numbers on the other hand can be reused across multiple mobile phone operators. 68

69 Roaming Mobile Devices A mobile phone is registered with a home mobile phone network operator. An agreement of billing must exist between the visited and the home phone networks. Different phone operators may charge different fees for roaming mobile phones. 69

70 Mobile Internet Access A modern mobile phone has both mobile data network and WiFi data network capabilities. Mobile data network is not free, while most WiFi networks are free. Mobile data network has a better coverage and provides a true roaming experience. 70

71 3G Modem and WiFi Router 71

72 4G Mobile Data Networks The 4 th generation mobile data network standards include LTE and WiMax. LTE (Long Term Evolution) is capable of up to 100 Mbps per mobile device. WiMax (similar to WiFi) is capable of up to 50 Mbps with a range of 10 Km. 72

73 The End. 73