IST 1010 Introduction to information technology

1. IST 1010 Introduction to information technology 9th Feb 2011

2. Agenda • Overview: communication, computer networks • Telecommunication: Media, etc • Types of networks: PAN, LAN, MAN, WAN • Network topologies • Carriers and services • Distributed, centralized,

3. Communications • Communications • The message (data and information) is communicated via the signal • The transmission medium “carries” the signal Transmissionmedium Sender Receiver Signal

4. Computer Networks • A computer network is a system for communicating between two or more computers and associated devices. It is an interconnection of computers for the purposes of sharing information and resources. • A popular example of a computer network is the internet, which allows millions of users to share information • Computer networks can be classified according to their size: • Personal area network (PAN) • Local area network (LAN) • Metropolitan area network (MAN) • Wide area network (WAN)

5. An example of a network Router Hub Bridge Segment Node Hub Internet

6. Telecommunications • Telecommunications • The electronic transmission of signals for communications, including such means as: • Telephone • Radio • Television • Telecommunication medium • Anything that carries an electronic signal and interfaces between a sending device and a receiving device

7. Communications and Telecommunications • In human speech, the sender transmits a signal through the transmission medium of the air • In telecommunications, the sender transmits a signal through the transmission medium of a cable Schematic

9. Data Communications • Data communications • A specialized subset of telecommunications that refers to the electronic collection, processing, and distribution of data -- typically between computer system hardware devices

10. Elements of a Telecommunications System • Telecommunication devices • Relay signals between computer systems and transmission media Schematic

12. Computer Network • Computer network… • The communications media, devices, and software needed to connect two or more computer systems and/or devices • Used to share hardware, programs, and databases across the organization • Fosters teamwork, innovative ideas, and new business strategies

13. Types of Telecommunications Media (1) • Twisted pair wire cable • Insulated pairs of wires historically used in telephone service and to connect computer devices • Coaxial cable • Consists of an inner conductor wire surrounded by insulation, called the dielectric • The dielectric is surrounded by a conductive shield, which is surrounded by a non-conductive jacket. Coaxial cable has better data transmission rate than twisted pair

14. Types of Telecommunications Media (2) • Fiber-optic Cable • Many extremely thin strands of glass or plastic bound together in a sheathing which transmits signals with light beams • Can be used for voice, data, and video

15. Personal Area Network • A PAN is a network that is used for communicating among computers and computer devices (including telephones) in close proximity of around a few meters within a room • It can be used for communicating between the devices themselves, or for connecting to a larger network such as the internet • PAN’s can be wired or wireless • PAN’s can be wired with a computer bus such as a universal serial bus: USB (a serial bus standard for connecting devices to a computer, where many devices can be connected concurrently) • PAN’s can also be wireless through the use of bluetooth (a radio standard designed for low power consumption for interconnecting computers and devices such as telephones, printers or keyboards to the computer) or IrDA (infrared data association) technologies

16. Local Area Network • A LAN is a network that is used for communicating among computer devices, usually within an office building or home • LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users • Is limited in size, typically spanning a few hundred meters, and no more than a mile • Is fast, with speeds from 10 Mbps to 10 Gbps • Requires little wiring, typically a single cable connecting to each device • Has lower cost compared to MAN’s or WAN’s

17. LAN basics • LAN’s can be either wired or wireless. Twisted pair, coax or fiber optic cable can be used in wired LAN’s • Nodes in a LAN are linked together with a certain topology. These topologies include: • Bus • Ring • Star • Branching tree

18. A node is defined to be any device connected to the network. This could be a computer, a printer, a router, etc. • A Hub is a networking device that connects multiple segments of the network together • A Network Interface Card (NIC) is the circuit board that has the networking logic implemented, and provides a plug for the cable into the computer (unless wireless). In most cases, this is an Ethernet card inserted in a slot of the computer’s motherboard

19. The Network Operating System (NOS) is the software (typically part of the operating system kernel) that communicates with the NIC, and enables users to share files and hardware and communicate with other computers. Examples of NOS include: Windows XP, Windows NT, Sun Solaris, Linux, etc..

20. Network Topologies • Network Topology • A logical model that describes how networks are structured or configured

21. Network Topologies • Bus Topology • Each node is connected one after the other (like christmas lights) • Nodes communicate with each other along the same path called the backbone

22. Ring Topology • The ring network is like a bus network, but the “end” of the network is connected to the first node • Nodes in the network use tokens to communicate with each other Backbone

23. Hub • Star Topology • Each node is connected to a device in the center of the network called a hub • The hub simply passes the signal arriving from any node to the other nodes in the network • The hub does not route the data

24. Branching Tree Topology

26. Multiplexer • Multiplexer • Allows several telecommunications signals to be transmitted over a single communications medium at the same time Pretty picture

27. Communicationslink Multiplexor Front-endprocessor Hostcomputer

28. Front-End Processor • Front-end processor… • Special purpose computers that manage communication to and from a computer system Pretty picture

29. Job 1 Incoming and outgoing jobs Job 2 Job 3 Front-endprocessor Mainsystem Job 4

30. Carriers and Services (1) • Carriers • Organizations that take the responsibility of ensuring telecommunications can effectively take place between enterprises • Common carriers • Long-distance telephone companies • Value-added carriers • Companies that have developed private telecommunications systems and offer their services for a fee • Switched lines • Lines that use switching equipment to allow one transmission device to be connected to other transmission devices (e.g., standard telephone line) • Dedicated line • A line that provides constant connection between two points. No switching or dialing is needed

31. Carriers and Services (2) • Private branch exchange (PBX) • Communication system that can manage both voice and data transfer within a location (e.g. a building) and to outside lines • Wide area telecommunication service (WATS) • Billing method for heavy users of voice services • Phone and dialing services • Includes automatic number identification (a.k.a. caller ID) • Integration of telephones and personal computers • Access code screening • Call priorities • One number portability (use anywhere) • Intelligent dialing (auto re-dial for a busy number)

32. Carriers and Services (3) • ISDN • ISDN = Integrated Services Digital Network • Technology that uses existing common-carrier lines to simultaneously transmit voice, video, and image data in digital form Pretty picture

34. Networks and Distributed Processing • Centralized processing • Data processing that occurs in a single location or facility • Decentralized processing • Data processing that occurs when devices are placed at various remote locations • Distributed processing • Data processing that occurs when computers are placed at remote locations but are connected to each other via telecommunications devices

35. Network Concepts and Considerations • Other network topologies • A topology is a logical model that describes how networks are structured or configured • Hierarchical • Hybrid

36. Hierarchical • Uses treelike structures with messages passed along the branches of the hierarchy • Hybrid • Network made up of various types of topologies

37. Network Types • Local area network (LAN) • Connects computer systems and devices in the same geographic area (can be Ring, Bus, Hierarchical, Star, Hybrid) • Wide area network (WAN) • Ties together large geographic regions using microwave and satellite transmission or telephone lines • International network • Links systems between countries

38. Terminal-to-Host Connection • Applications and databases reside on the same host computer • User interacts with the application using a “dumb terminal” Target PC “dumb terminal” Hostcomputer REF: the thin-client set up at USIU – where you can’t use flash disks

39. File Server Connection • Applications and databases reside on the same host computer • File server transfers data and programs to PCs on the network, where these target PCs perform most of the processing Target PC File downloaded to user File server Hostcomputer

40. Client/Server Connection • Applications and databases reside on specialized host computers • Servers do most or all of the processing and transmit the results to the client Client Server Server Client Server

41. Advantages & Disadvantages of Client/Server Advantages • Reduced cost potential • Improved Performance • Increased Security • Disadvantages • Increased cost potential • Loss of control • Complex multi-vendor environment

42. Communications Software and Protocols (1) • Communications software • Provides error checking, message formatting, communications logs, data security and privacy, and translation capabilities for networks • Network operating system (NOS) • Systems software that controls the computer systems and devices on a network and allows them to communicate with each other • Network management software • Enables a manager on a networked desktop to monitor the use of individual computers and shared hardware, scan for viruses, and ensure compliance with software licenses

43. Communications Software and Protocols (2) • Protocol • Rules that ensure communications among computers of different types and from different manufacturers.

44. Communications Software and Protocols (3) • Open Systems Interconnection (OSI) Model • Serves as a standard model for network architectures and is endorsed by the International Standards Committee • Communication functions are represented in seven layers to promote the development of modular networks. Designed to permit communication among different computers from different operating systems • Seven layers (see figure 6.20)

45. Communications Software and Protocols (4) • TCP/IP • TCP/IP = Transmission Control Protocol/Internet Protocol Standard originally developed by the U.S. government to link defense research agencies; it is the primary communication protocol of the Internet • Systems Network Architecture (SNA) • IBM communication protocol • Ethernet • Protocol standard developed forLANs using a bus topology • X.400 and X.500 • An international standard for message handling and network directories

46. Telecommunications Applications (1) • Linking personal computers to mainframe computers • Download and upload information • Voice mail • Enables users to leave, receive, and store verbal messages for and from other users • Electronic mail (e-mail) • Enables a sender to connect a computer to a network, type messages, and send it to another person on the network

47. Telecommunications Applications (3) • Videoconferencing • Allows participants to conduct long-distance meetings “face to face” while eliminating Pretty picture

49. Thanks