Computer Network

1. Computer Network Chapter 4

2. “I think there is a world of market for maybe five computers” Thomas J. Watson Chairman IBM, 1943

3. Why Use Networks? • Network • Group of computers and devices • Connected by transmission media • Stand-alone computer • Not connected to other computers • Uses local software and data • Advantages of networks over standalone computers • Device sharing by multiple users • Saves money and time • Central network management

4. Types of Networks • Network models • Peer-to-Peer • Client/server

5. Figure 1-1 Resource sharing on a simple peer-to-peer network Peer-to-Peer Network

6. Figure 1-2 Resource sharing on a client/server network Client/Server Networks

7. Networks are everywhere • Computers • Printer • Copier • Fax • Scanner • Personal Digital Assistants • Cell Phones • Radios • RFID (Radio Frequency ID)

8. Introduction • Today people are often linked by wires or air (wireless) carrying voice and computer signals via the telephone system. • Data communications dominate the world. • Computer Network: The linkage of computer systems by means of communication lines or channels (e.g., fiber optic, microwave, satellite, telephone line, 802.11)

9. Computer Network • At least two computers need to be connected • Copper • Fiber Optics • Microwaves • Infrared • Satellites

10. Data Communications Data Processing + Telecommunications = Data Communications

11. Data Communication • Electronic transfer of information from one computer to another. • Data • Text • Pictures • Graphics • Video • Voice

12. Network Components (Examples) Links Interfaces Switches/routers Ethernet card Large router Fibers Wireless card Introduction Coaxial Cable Switch

13. Why network? • Resource sharing • Files, Applications, Printer, Fax • Communication Medium • Email, Collaboration, videoconferencing • E-business • Supply-chain, inventory, B2C

14. Business Applications of Networks • A network with two clients and one server.

15. Business Applications of Networks (2) • The client-server model involves requests and replies.

16. Home Network Applications • Access to remote information • Person-to-person communication • Interactive entertainment • Electronic commerce

17. Communication Lines/Channels • Fiber optic • Microwave • Satellite • Telephone Line etc.

18. Impact of Data Communications • It enables information to be accessed and transmitted quickly. • Automatic Data Collection or Polling (i.e. Chuck E. Cheese) –menu update, get info from POS • It allows the storing of information in a centralized database that may be shared by a few users in a small computer network or by thousands of users in a large computer network. • It facilitates centralized management and decentralized operations (e.g., restaurant chain).

19. Impact of Data Communications • It links business processes performed by independent computer systems to improve organizational efficiency and effectiveness • It links a business to its customers • Communication devices, such as cell phones, personal digital assistants, etc.

20. Local Area Network • LAN is linkage of computers in a specific geographical area (usually within an office or building) such as in hotels, restaurants, or country clubs using transmission medium such as twisted pair wire or coaxial cable.

21. Why Local Area Network (LAN)? • Increased processing and transfer requirements in many graphics-intensive applications now require significantly higher transfer rates (data, audio, image, video) • Decreased cost of storage space leads to program and file bloat, increased need for transfer capacity • Watch this video

22. Basic LAN Hardware • Computers/Server(s) • Resources • Cables • Connectors (Hubs) • Network Interface Cards (Ethernet) ADVANCED • Bridges • Routers

24. Full versus half duplex • Half duplex: communication can happen in both directions but one at a time (like walkie-talkie) • Full duplex: communication can happen in both directions at the same time (like a phone)

25. Client • Is any network entity that can request resources from the network. • Workstations can be clients but not all clients are workstations • For example, a printer can request resources from the network, it is a client, not a workstation.

26. Server • A computer that provides resources to the clients on the network. • Servers are typically powerful computers

27. Switch

28. Hub vs. Switch • Hub—sends signals to all computers connected • Switch– sends signals to intended computer(s)

29. LANs share • Files (databases) • Resources (Printers, fax) • Programs (Fidelio, MS Office) • Working together • Communication

30. WAN (Wide Area Network ) Communications Hardware • WAN=Connection of at least two LANs • Down-line processor/ Multiplexer • Front-end Processor • PBX(Private Branch Exchange) • Watch Video

31. WAN Connection Types • Private Lines • Frame Relay • Dial-Up • Satellite • Down Line Processor or Multiplexer • Front-end Processor • PBX Switchboard • Shared Lines • DSL • Cable

32. WAN in Hospitality • Global Reservation System • Central Reservation System • Property Management System

33. LA Miami NYC Boston

34. Hotel Marriott Miami Hotel Marriott NYC • Dial-up (max 56Kbps) • ISDN (128Kbps) • DSL (1.5Mbps) • Cable (3.5Mbps) Shared Connection

35. Hotel Marriott Miami Hotel Marriott NYC • T-1 (1.5Mbps) • Frame Relay (1.5Mbps) • T-3 (43Mbps) • OC3 (155Mbps) • ATM (622Mbps) Dedicated Connection

36. Hotel Marriott NYC • 802.11b (11Mbps) • 802.11g (54Mbps) • 802.11a (54Mbps) • 802.11n (<100Mbps) WLAN -Dedicated / Shared Connection

37. A Small LAN

38. Wireless LAN • Advantages • Wireless LANs are simple to set up. It literally can take 10 minutes for a simple wireless network to be setup. • Wireless LANs are cheap to create. • When it is not possible to wire, Wireless LANs come into rescue. • Disadvantages • Security is the biggest down side of wireless LANs.

40. HP Server IBM Server

41. Network Hardware: Repeaters • Extend the length of transmission media

42. Server Types • File Server: holds and distributes files • Print Server: handles printing jobs from clients • Proxy Server: performs a function on behalf of other computers • Application Server: hosts a network application (i.e. Marriott’s central reservation system, Marsha) • Web Server: handles web pages and other web content (i.e. Marriott.com, Hilton.com, Starwood.com) • Mail Server: hosts and delivers electronic mail. • Fax Server: sends and receives faxes electronically. • Voice over IP Server: Handles calls on Internet Protocol

43. Physical Media • Coaxial Cable • Thinnet (BNC Connector and RG-58) • Twisted Pair Cable • Category 1 – Category 6 • RJ-11 and RJ-45 Connectors • Fiber Optic Cable

44. Coaxial Cable • Contains a center conductor, made of copper, surrounded by a plastic jacket • Teflon type covering  plenum-rated coating does not burn easily • Coax is not used in LANs today but still used widely by TV cable operators

45. Thin Ethernet • Thinnet • 10Base-2 • Thin coaxial cable– smaller than thick coaxial cable

46. A Stripped-back Thinnet

47. Thinnet

48. Connectors • With thinnet, you use BNC (BayoNet Connector) connectors to attach stations to the network. • BNC Connector locks securely with a quarter-twist motion • A T-connector is used to connect backbone devices

49. Male and Female BNC Connectors