TOPIC 1: Introduction to Data Comm & Networking

1. TOPIC 1: Introduction to Data Comm & Networking Anetwork,or communications network, is a system of interconnected computers, telephones, or other communications devices that can communicate with one another and share applications and data. Network

2. In Information Technology, networking is the construction, design, and use of network, including the physical hardware(cabling, hub, bridge, router and so forth), the selection and use of telecommunication protocol and computer softwarefor using and managing the network, and the establishment of operation policies and procedures related to the network.

3. 4.2 Benefits of networks Sharing of Programs & data Sharing of peripheral devices Access to databases Better Communications

4. Benefits of Networks People and organizations use computers in networks for severalreasons. These include the following: • Sharing of ___________________: Expensive devices such as printers, disk drives, and scanners can be shared. • Sharing of ___________________: People in an organization can use the same software and have the access to the same files. • Better _______________: Networks make e-mail possible, keeping everyone posted about important information. • Access to ____________: Networks enable users to tap into all kinds of databases.

5. 4.3 Types of Networks

6. An example of a local area network (LAN) in an office building.

7. An example of WAN

9. Most large computer networks have at least one host computer, a mainframe or midsize central computer that controls the network. • The other devices within the network are called nodes. A______is any device that is attached to a network—for example, a microcomputer, terminal, storage device, or printer.

10. A LAN can contain a variety of interconnected computers and peripherals.

11. WANs are often made up of LANs linked by phone lines, microwave towers, and communication satellites.

12. Local Area Network (LAN) Client/Server LAN Peer-to-Peer LAN

13. 4.4 Clients/ Server Vs Peer-to-Peer (a) Client-server LANs • One popular type of server-based network is the ________________ network, in which individual computers share the processing and storage workload with a __________ server. • A client-server LAN consists of clients, which are microcomputers that ___________ data, and servers, which are computers used to __________ data. • A server controls access to the hardware and software on the network and provides a centralized storage area for programs, data, and information. • The other computers on the network, called clients, rely on the servers for these resources, such as files, devices, processing power, and storage.

14. Computer transactions using the client/server model: • For example, to check your bank account from your computer, a client program in your computer sends a request to a database server at the bank computer to retrieve your account balance. The balance is returned back to your personal computer, which displays the information for you. • Relative to the Internet, your Web _________ is a client program that requests services from a Web ________ in another computer somewhere on the Internet. • The major difference between the server and the client computers is that the server ordinarily is fasterand has more storage space. • Some servers are dedicated to performing a special task.

15. EXAMPLE: • Server machine running maybank2u.com server • Your desktop computer running Internet Explorer Your browser connects to the server and request a page • What’s my bank account balance? The server sends back the requested page

17. Example Shared Print Server E ACCESS 1 E ACCESS 2 E ACCESS 3 Shared Network Printer

18. (b) Peer-to-peer LANs • In a _____________ LAN, all microcomputers (nodes) on the network have _________ relationships to all others, and all have similar types of software that support the sharing or resources. • Each computer on a peer-to-peer network can share the hardware (such as printer), data, or information located on any other computer in the network.

19. A ________ operating system and application software thus must be installed on each computer in the network. • Only one computer on the network, however, needs to connect to peripherals, such as a printer, scanner, or fax modem; the other computers on the network share these hardware resources. • On the Internet, peer-to-peer (referred to as _____) is a type of Internet network that allows a group of computer users with the same networking program to connect with each other and directly access files from one another's hard drives.

20. Corporations are looking at the advantages of using P2P as a way for employees to share files without the expense involved in maintaining a centralized server and as a way for businesses to exchange information with each other directly. • P2P LANs are also commonly set up in small organizations. P2P networks are popular in schools, where a network’s main benefit is shared storage and printers or enhanced communications.

21. Example : TBS staffroom

23. 4.5 Components Required for Networking • Connection or cabling system: LANs may use a wired or wireless connection system.Wired connections may be twisted-pair wiring, coaxial cable, or fiber-optic cable. Wireless connections may be infrared or radio-wave transmission. • Microcomputers with _________________ cards: A network interface card (inserted into an expansion slot in a PC) enables the computer to send and receive messages over a cable network. • Network operating system: The network operating system (NOS) is the system software that manages the activity of a network. • Other shared devices: Printers, scanners, storage devices, and other peripherals may be added to the network as necessary and shared by all users.

24. A_________ is a special computer that directs communicating messages when several networks are connected together. It determines a route for the packet to take toward its destination. A router accepts incoming data transmissions and distributes them to devices attached to its local network.

25. Hardware Required for Networking Router to WAN Shared hard disk bridge Printer Fiber-optic backbone bridge Local Printer Cabling

27. 4.6 Topology of LANs • The ____________, or shape, of a network is called a _________. • The three basic topologies are star, ring, and bus. • Networks also can use combinations of these topologies.

28. PC2 PC1 PC3 PC4 Central Hub Printer PC5 PC7 PC6 (a) Star network • A star network is one in which all microcomputers and other communications devices are connected to a _______ server, thus forming a star. • The center computer that provides a common connection point for devices in the network is called the ______. • All data that transfer from one computer to another passes through the hub.

29. The advantage of a star network is that the hub prevents collisions between messages. • Moreover, if a connection is broken between any communications device and the hub, the rest of the devices on the network will ________ operating. • However, if the _____ goes down, the entire network will stop.

31. PC1 PC2 PC4 PC 3 (b) Ring network • A ring network is one in which all microcomputers and other communications devices are connected in a continuous _____, or ring. • Electronic messages are passed around the ring until they reach the right destination. • There is no ________ server. • The advantage of a ring network is that messages flow in only one direction. Thus, there is no danger of collisions. • The disadvantage is that, if a connection is broken, the entire network stops working.

33. PC1 PC2 PC5 Printer PC3 PC4 terminal (c) Bus network • In a bus network, all communications devices are connected to a _________ channel. • The bus is the __________ cable that connects the computers and other devices. • The bus in a bus network can transmit data, instructions, and information in both directions. Only one device, such as a computer, can transfer items at one time, however. • Each communications device transmits electronic messages to other devices. If some of those messages collide, the device waits and tries to transmit again.

35. Bus networks are flexible in that computers and other devices can be attached or detached from the network at any point without disturbing the rest of the network. • Failure of one device also does not affect the rest of the bus network, the transmission simply bypasses the failed device. • The disadvantage is that extra circuitry and software are needed to avoid collisions between data. • Also, if a connection in the bus is broken—as when someone moves a desk and knocks the connection out—the entire network may stop working.

36. (d) Hybrid network • Hybrid networks are combinations of star, ring, and bus networks. • For example, a small college campus might use a bus network to connect buildings and star and ring networks within certain buildings.

38. Hybrid Network Terminal Computer Computer Printer Computer Printer Server Terminal Printer Computer Computer Computer Computer Terminal Terminal Computer Computer Printer Computer