1. Introduction to Computer Science Computer Networks, Web & Internet

2. 2 What is Communication Communication is simply the act of transferring information from one place to another.

3. What is (Computer) Network A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. 3

4. What is (Computer) Network The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. 4

5. 5 Network Channels Communications Channels Communications Channel / Communications Medium: The physical or cable-less media that link the different components of a network..

6. Network Channels Communications Channels (Continued) Physical Channels: – Twisted Pair: A physical communications channel that uses strands of copper wire twisted together in pairs to form a telephone wire. 6

7. Network Channels Communications Channels (Continued) Physical Channels: – Coaxial Cable/Co-ax: A physical communications channel that uses one or more central wire conductors surrounded by an insulator and encased in either a wire mesh or metal sheathing. 7

8. 8 Network Channels Communications Channels (Continued) Physical Channels: – Coaxial Cable/Co-ax: Baseband Cable: Carries a single communication or message at very high megabit speeds, is often used in local area networks. Broadband Cable: Carries multiple signals – data, voice, and video – simultaneously; each signal can be a different speed.

9. 9 Network Channels Communications Channels (Continued) Physical Channels: – Fiber-optic Cable: A physical communications channel that uses light and glass fibers.

10. 10 Network Channels Communications Channels (Continued) Wireless Channels – Wireless: Wireless channels transmit data using radio signals sent through air or space rather than over wire or optical cables. – Microwave: A cableless medium that uses high-frequency radio signals to send data or information through the air. – Satellite: A cableless medium in which communications are beamed from a microwave station to a communications satellite to orbit above the earth and relayed to other earth stations.

11. 11 Network Channels Communications Channels (Continued) Wireless Channels – Satellite Low-earth-orbit satellite (LEO): Because they circle Earth at a distance far closer than other satellites, LEO satellite systems offer significant advantages: they do not have the comparatively long propagation delays, do not require use of bulky, expensive, directional antennas, less expensive to produce and to launch into orbit. However, greater numbers are needed to provide coverage for a geographic because they do orbit closer to Earth. Very Small Aperture Terminal (VSAT): A satellite earth station with an antenna diameter of under one meter.

12. 12 Network Channels Communications Channels (Continued) Wireless Channels – Infrared: A cableless medium that transmits data and information in coded form by means of an infrared light beamed from one transceiver to another. Transceiver: A combination transmitter and receiver that transmits and receives data and information.

13. 13 Network Channels Communications Channels (Continued) Wireless Channels – Radio Waves Radio Wave Transmission/Radio Frequency (RF) Transmission: A cableless medium that uses frequencies rented from public radio networks to transmit data and information.

14. 14 Principles of Communications Networks Definition Communication: The sending and receiving of data and information over a communication’s network. Multiuser System: A communications system in which more than one user share hardware, programs, information, people, and procedures.

15. 15 Principles of Communications Networks Role of Communications Networks Communications Network: A set of locations, or nodes, consisting of hardware, programs, and information linked together as a system that transmits and receives data and information. Node: A communication station within a network.

16. 16 Network Service Applications Definition Network Services: The applications available on a communications network. Electronic Mail – Electronic Mailbox: An area of space on magnetic disk in a server or host computer that is allocated for storing an individual’s e-mail.

17. 17 Network Service Applications Definition (Continued)

18. 18 Network Service Applications Definition (Continued) Voice Mail: A system that captures, stores, and transmits spoken messages using an ordinary telephone connected to a computer network. – PPTs (post, telephone, and telegraph companies): A general term for telephone companies outside the United States. – Unified Messaging Systems: Offers users the ability to manage several communications media, including telephone, fax, e-mail (including those from the Web), and voice mail through a central message manager.

19. 19 Network Service Applications Definition (Continued)

20. 20 Network Service Applications Definition (Continued) Videoconferencing: A type of conferencing in which video cameras and microphones capture the sight and sound of participants for transmission over a network. – Web-casting: Uses the reach of the Internet to link people from anywhere in the world into a conference. Work Group Conferencing: A type of conferencing that uses a software package called groupware to interconnect participants’ computers at their various locations. Participants interact through a microcomputer directly linked to a server and their comments are broadcast to all others taking part in the conference.

21. 21 Network Service Applications Definition (Continued) Electronic Bulletin Board: A network service application that allows messages and announcements to be posted and read. It is accessed by dialing a telephone number and interconnecting with the bulletin board through a modem. Electronic Funds Transfer (EFT): The movement of money over a network.

22. 22 Network Service Applications Definition (Continued)

23. 23 Network Service Applications Definition (Continued) Electronic Data Interchange (EDI): A form of electronic communication that allows trading partners to exchange business transaction data in structured formats that can be processed by application software.

24. 24 Types of Network Definition Topology: A network configuration, or the arrangement of the nodes or workstations of a network in relation to one another.

25. 25 Types of Network Definition (Continued)

26. 26 Types of Network Wide Area Networks Wide Area Network (WAN): A network that connects sites dispersed across states, countries, or continents. Common Carrier: A company that furnishes public communications facilities for voice and data transmission. T-Carrier: A very high-speed channel designed for use as the backbone of a network and for point-to- point connection of locations.

27. 27 Types of Network Local Area Networks Local Area Network (LAN): A network that interconnects computers and communications devices within an office or series of offices; typically spans a distance of a few hundred feet to several miles. Workstation/Client: A desktop computer connected to a network.

28. 28 Types of Network Local Area Networks (Continued)

29. 29 Types of Network Metropolitan Area Networks Metropolitan Area Network (MAN): A network that transmits data and information over citywide distances and at greater speeds than a LAN.

30. 30 Origin of the Internet Definition What is internet?

31. 31 Origin of the Internet Definition Internet/the Net: A communication network that is itself a connection of many other networks.

32. 32 So, who owns the Internet? Well, nobody does. No single person or company owns the Internet or even controls it entirely. As a wide-area network, it is made up of many smaller networks. These smaller networks are often owned and managed by a person or organization. The Internet, then, is really defined by how connections can be made between these networks.

33. 33 Origin of the Internet Computers on the Internet Client Computer: The computer that accesses the information stored on a server computer. Server Computer: The computer that contains data and information that can be accessed by a client computer.

34. 34 Origin of the Internet Computers on the Internet (Continued) Client-server Computing: A type of computing in which all data and information retrieval requests and responses pass over a network. Much of the processing is performed on the server and the results of the processing are transmitted to the client. Surf or Surfing: Moving among a number of networks that are linked together, or inter-networked.

35. 35 Capabilities of the Internet Three Main Functions Communicate Retrieve Shop, Buy, and Sell

36. 36 Capabilities of the Internet Communications Capabilities E-mail or Electronic Mail: A service that transports text messages from a sender to one or more receivers via computer. Mailing Lists: Each mailing list has subscribers who receive messages as part of an ongoing discussion of the list’s topic. – Moderated: A mailing list in which the messages are first screened by an individual to determine their suitability given the purpose of the list.

37. 37 Capabilities of the Internet Communications Capabilities (Continued) Newsgroups: Worldwide discussion areas where notices can be posted for anyone to view. Chat Session or Internet Relay Chat (IRC): A live interactive discussion in which parties on the network exchange ideas and observation electronically.

38. 38 Capabilities of the Internet Communications Capabilities (Continued) Instant Messages: A combination of real-time chat and e-mail by which short text messages are rapidly exchanged over the Internet, with messages appearing on recipient’s display screen immediately upon arrival. Internet Telephony or Voice Over the Internet or Voice over IP: Real-time voice conversations transmitted between computers on the Internet.

39. 39 Capabilities of the Internet Communications Capabilities (Continued) Telnet: A network capability that permits remote sign-on to any computer on the Internet from the computer an individual is using at that time.

40. 40 Capabilities of the Internet Retrieval Capabilities FTP (File Transfer Protocol): Used for transferring files containing documents or software between computers on the Internet. Web Directory: A listing of Web sites and their URLs, categorized by topic. – Keyword: A string of letters or words that indicates the subject to be searched. Search Engines: Software programs that look through the Web to locate sites matching a keyword entered by the user.

41. 41 Capabilities of the Internet Retrieval Capabilities (Continued) Portal: A gateway or hub on the Internet from which other sites can be visited. – Vertical Portal or Vortal: A Web site that specializes in providing information related to a particular industry such as automobiles, healthcare, or investments. – Horizontal Portal: Provides services and links to Web sites of interest to a wide variety of users.

42. 42 Capabilities of the Internet Retrieval Capabilities (Continued) Webcasting: The prearranged delivery, or push, of information of interest to a user’s desktop automatically. Streaming: An on-demand retrieval and playing of audio, video, or other media that can occur while the downloading is occurring.

43. 43 Capabilities of the Internet Shop, Buy, and Sell Electronic Commerce/e-commerce: Conducting commercial activities on the Internet.

44. 44 The Internet Community Definition Internet Users Service Providers or Internet Service Providers (ISPs): A company that sells communications services that enable users to access the Internet. Application Service Providers (ASPs): Companies that develop, install, and operate (or host) an information technology application on the Internet for the user, charging a recurring fee for doing so.

45. 45 The Internet Community Definition (Continued) Content Providers: Individuals or companies that furnish the information available on the Internet.

46. 46 The Internet Community Definition (Continued) Infrastructure Providers – Network Infrastructure Providers: Companies, such as telephone, cellular telephone, cable TV, and satellite transmission companies, that operate the network of communication channels that carry data and information to and from user and content locations. – Component Infrastructure Providers: Companies that supply the computer hardware and software that makes it possible to use, operate, or store and retrieve content from the Internet.

47. 47 The Internet Community Definition (Continued) Internet Support Agencies – Internet Corp. for Assigned Names and Numbers (ICANN): The nonprofit corporation that was formed to assume responsibility for the IP address space allocation, protocol parameter assignment, domain name system management, and root server system management. – Internet Engineering Task Force (IETF): A large international community of network designers, operators, vendors, and researchers concerned with the evolution of Internet architecture and the smooth operation of the Internet.

48. 48 The Internet Connection Internet backbone A set of high-speed networks that carry Internet traffic. These networks are provided by companies such as AT&T, GTE, and IBM Internet service provider (ISP) A company that provides other companies or individuals with access to the Internet

49. 49 The Internet Connection There are various technologies available that you can use to connect a home computer to the Internet – A phone modem converts computer data into an analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data – A digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office – A cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth

50. 50 The Internet Connection Broadband A connection in which transfer speeds are faster than 128 bits per second – DSL connections and cable modems are broadband connections – The speed for downloads (getting data from the Internet to your home computer) may not be the same as uploads (sending data from your home computer to the Internet)

51. 51 Internet Addresses Addresses on Host Computers E-mail Addresses World Wide Web Addresses – Uniform Resource Locator (URL): A document’s address on the WWW. FTP Addresses

52. 52 Internet Addresses Network Addresses Hostname A unique identification that specifies a particular computer on the Internet For example: - matisse.csc.villanova.edu - condor.develocorp.com

53. 53 Internet Addresses Network Addresses Network software translates a hostname into its corresponding IP address For example 205.39.145.18

54. 54 Internet Addresses Network Addresses An IP address can be split into – network address, which specifies a specific network – host number, which specifies a particular machine in that network

55. 55 Internet Addresses Domain Name A hostname consists of the computer name followed by the domain name csc.villanova.edu is the domain name – A domain name is separated into two or more sections that specify the organization, and possibly a subset of an organization, of which the computer is a part – Two organizations can have a computer named the same thing because the domain name makes it clear which one is being referred to

56. 56 Internet Addresses Domain Name The very last section of the domain is called its top-level domain (TLD) name

57. 57 Internet Addresses Domain Name Organizations based in countries other than the United States use a top- level domain that corresponds to their two-letter country codes

58. The End Thank You