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3. Data Communications

3. Data Communications 3.4 Internet – Internet Connection Internet/Intranet The development of the Internet The development of IT as a timeline Difference between intranet and the Internet Functions of a typical school intranet The development of the Internet

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3. Data Communications

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  1. 3. Data Communications 3.4 Internet – Internet Connection

  2. Internet/Intranet • The development of the Internet • The development of IT as a timeline • Difference between intranet and the Internet • Functions of a typical school intranet

  3. The development of the Internet It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969 and was first known as the Advanced Research Projects Agency Network. The original aim was to create a network that would allow users of a research computer at one university to be able to "talk to" research computers at other universities. Extracted from whatis.com

  4. The development of the Internet A side benefit of ARPANet's design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster. Extracted from whatis.com

  5. The development of the Internet • A global network connecting millions of computers. As of 1999, the Internet has more than 200 million users worldwide, and that number is growing rapidly. More than 100 countries are linked into exchanges of data, news and opinions. Extracted from pcwebopaedia.com

  6. The development of IT as a timeline • Please refer to the following website spider.georgetowncollege.edu/infoweb/ AcademicSupport/classes/ITClass/ Powerpoint/it1/sld007.htm

  7. Cellular Telephone Telegraph Television Satellite 1970s 1800s 1880s 1930s 1890s 1950s 1840s Fibre Optics Computer Fax Radio The development of IT as a timeline

  8. Intranet • Share information • Less expensive to build and manage than private networks • A network based on TCP/IP protocols • Belong to an organisation, usually a corporation • Accessible only by the organisation’s members, employees or others with authorisation • An intranet’s web sites look and act like any other web sites • The firewall surrounding an intranet fends off unauthorised access

  9. Functions of a typical school intranet • E-mailing • Password • Chat room • Message board • Notice board • File cabinet • Question database • Library service

  10. Internet Connection • Essential components: • Dial-up software • Telephone lines • ISP • Leased lines • Connection services: • ISDN • Cable • ADSL

  11. Dial-up software Microsoft Dial-up program Reference links: www.download.com, tucows.hkstar.com

  12. Telephone lines Registered Jack-11 (RJ-11) www.techweb.com/encyclopedia/

  13. The Internet HKIX ISP ISP ISP ISPs in HK ISP – Internet Services Provider HKIX – Hong Kong Information Exchange

  14. Leased lines • a permanent telephone connection between two points set up by a telecommunications common carrier. • are typically used by businesses to connect geographically distant offices • always active • The fee for the connection is a fixed monthly rate • the carrier can assure a given level of quality

  15. Leased lines • a T-1 channel is a type of leased line that provides a maximum transmission speed of 1.544 Mbps • You can divide the connection into different lines for data and voice communication or use the channel for one high speed data circuit

  16. ISDN • Integrated Services Digital Network is an international communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires • ISDN supports data transfer rates of 64 Kbps • two lines at once, called B (bearer) channels • one for voice and the other for data, or you can use both lines for data to give you data rates of 128 Kbps • Detailed references: www.webopaedia.com, www.techweb.com/encyclopedia

  17. ISDN

  18. ISDN

  19. Cable modem • A modem used to connect a computer to a cable TV service that provides Internet access. • Cable modems can dramatically increase the bandwidth between the user's computer and the Internet service provider • Cable modems link to the computer via Ethernet, which makes the service online all the time • the speed will vary depending on how many customers on that cable segment are using the Web at the same time

  20. Cable modem

  21. Cable modem

  22. ADSL • Asymmetric Digital Subscriber Line, a new technology that allows more data to be sent over existing copper telephone lines (POTS). • ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate).

  23. TCP/IP • A protocol is a set of special rules governing transmitting and receiving of data between end points • TCP – Transmission Control Protocol • IP – Internet Protocol • Refer to the handouts of chapter 3.2 for the functions of TCP and IP

  24. IP Address • An identifier for a computer or device on a TCP/IP network • The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. • Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.

  25. IP address classes • Class A addresses are for large networks with many devices. • Class B addresses are for medium-sized networks. • Class C addresses are for small networks (fewer than 256 devices). • Class D addresses are multicast addresses.

  26. Class A IP addresses 0XXXXXXX.xxxxxxxx.xxxxxxxx.xxxxxxxx Network ID Host ID

  27. Class B IP addresses 10XXXXXX.XXXXXXXX.xxxxxxxx.xxxxxxxx Network ID Host ID

  28. Class C IP addresses 110XXXXX.XXXXXXXX.XXXXXXXX.xxxxxxxx Network ID Host ID

  29. Class D IP addresses 1110xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx Multicast address

  30. Subnet mask • The method used for splitting IP networks into a series of subgroups, or subnets. • The mask is a binary pattern that is matched up with the IP address to turn part of the host ID address field into a field for subnets. • It's called a mask because it can be used to identify the subnet to which an IP address belongs by performing a bitwise AND operation on the mask and the IP address

  31. Subnet mask E.g. with explanations: Subnet mask: 255.255.255.0 (11111111.11111111.11111111.00000000) IP address: 150.215.17.9 (10010110.11010111.00010001.00001001) Subnet address: 150.215.17.0 (10010110.11010111.00010001.00000000)

  32. Subnet mask E.g. with explanations: Subnet mask: 255.255.240.0 (11111111.11111111.11110000.00000000) IP address: 150.215.17.9 (10010110.11010111.00010001.00001001) Subnet address: 150.215.16.0 (10010110.11010111.00010000.00000000)

  33. Default subnet mask numbers

  34. Reserved IP addresses • 127.X.X.X • Loop back • X.X.X.0 • Network • X.X.X.255 • Broadcasting

  35. DNS • Short for Domain Name System (or Service), an Internet service that translates domain names into IP addresses • Because domain names are alphabetic, they're easier to remember • The Internet however, is really based on IP addresses • Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 198.105.232.4.

  36. DNS • The DNS system is, in fact, its own network • If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned

  37. Routers • A device that forwards data packets from one local area network (LAN) or wide area network (WAN) to another • Based on routing tables and routing protocols, routers read the network address in each transmitted frame and make a decision on how to send it based on the most expedient route (traffic load, line costs, speed, bad lines, etc.)

  38. Install TCP/IP Network Fig. 1

  39. Install TCP/IP Add Fig. 2

  40. Install TCP/IP Add Protocol Fig. 3

  41. Install TCP/IP TCP/IP protocol Fig. 4

  42. Configure TCP/IP Dynamic Host Configuration Protocol (DHCP) Fig. 5

  43. Configure TCP/IP IP address Subnet mask Fig. 6

  44. TCP/IP Utilities • ping (Packet Inter-Network Groper) • This is used to test whether the host is reachable or not. • ping 10.123.48.173 • ping www.yahoo.com

  45. TCP/IP Utilities • nslookup (name service lookup) • This is used to find the web address from the IP address or vice and versa • nslookup 10.123.48.173 • nslookup www.yahoo.com

  46. TCP/IP Utilities • tracert (trace route) • This is used to show the path of the packet which has passed through on its way to destination. • tracert www.koei.co.jp • tracert www.netvigator.com

  47. TCP/IP Utilities • netstat (network statistics) • This is used to view TCP/IP statistics and the current active TCP/IP connections • netstat

  48. TCP/IP Utilities • ipconfig (IP configuration) • This is used to list the IP configuration of the current computer • ipconfig • ipconfig /all

  49. TCP/IP Utilities • arp (Address Resolution Protocol) • This is used to displays and modifies the IP-to-Physical address translation tables • arp -a

  50. Firewall • A firewall is special software or hardware designed to protect a private computer network from unauthorized access. Firewalls are used by corporations, banks and research facilities to keep information private and secure.

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