I think there is a world of market for maybe five computers Thomas J. Watson Chairman IBM, 1943
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
Types of Networks Network models Peer-to-Peer Client/server
Peer-to-Peer Network Figure 1-1 Resource sharing on a simple peer-to-peer network
Client/Server Networks Figure 1-2 Resource sharing on a client/server network
Networks are everywhere » Computers » Printer » Copier » Fax » Scanner » Personal Digital Assistants » Cell Phones » Radios » RFID (Radio Frequency ID)
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)
Computer Network At least two computers need to be connected Copper Fiber Optics Microwaves Infrared Satellites
Data Communications Telecommunications Data Processing = Data Communications +
Data Communication Electronic transfer of information from one computer to another. Data Text Pictures Graphics Video Voice
Why network? Resource sharing –Files, Applications, Printer, Fax Communication Medium –Email, Collaboration, videoconferencing E-business –Supply-chain, inventory, B2C
Business Applications of Networks A network with two clients and one server.
Business Applications of Networks (2) The client-server model involves requests and replies.
Home Network Applications Access to remote information Person-to-person communication Interactive entertainment Electronic commerce
Communication Lines/Channels Fiber optic Microwave Satellite Telephone Line etc.
Impact of Data Communications 1.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 2.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. 3.It facilitates centralized management and decentralized operations (e.g., restaurant chain).
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.
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.
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
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)
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.
Server A computer that provides resources to the clients on the network. Servers are typically powerful computers
Wireless LAN Advantages 1.Wireless LANs are simple to set up. It literally can take 10 minutes for a simple wireless network to be setup. 2.Wireless LANs are cheap to create. 3.When it is not possible to wire, Wireless LANs come into rescue. Disadvantages 1.Security is the biggest down side of wireless LANs.
Network Hardware: Repeaters Extend the length of transmission media
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. Marriotts 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
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
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
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
F type connector Popular with TV Cable and Cable Modems
Twisted-pair cable Consists of multiple, individually insulated wires that are twisted together in pairs Sometimes a metallic shield is placed around pairs shielded twisted pair (STP) Unshielded twisted pair (UTP)
Why twisted? Electromagnetic signals create interference crosstalk Twisting the cables in pairs reduce intereference Most common cable
Twisted-pair Cheaper Easy to work with Transmission rates are good
Fiber Optic Cable A glass or plastic fiber that carries light along its length. This cable is the fastest and most expensive transmission medium in the world today
Advantages of Fiber Optic Cable Superior System Performance Greatly increased bandwidth and capacity Lower signal loss Immunity to Electrical Noise Immune to noise (electromagnetic interference [EMI] and radio-frequency interference [RFI] Lower bit error rates Signal Security Difficult to tap Light weight
Topology Arrangement of workstations in a shared medium environment Logical arrangement (data flow) Physical arrangement (cabling scheme)
Network Topologies The manner in which workstations are connected together physically and logically is referred to as a NETWORK TOPOLOGY. 4 Types: Bus (Video)Video Ring (Video)Video Star (Video)Video Hybrid
Why Hybrid (Tiered)? Reliabilityless service interruption Capacity- not easily saturated Cost – low cost networks can build up Needs- not every department need the same equipment (accounting vs. graphics)
Network Management Network management is a systematic approach to planning, organizing, and controlling networks. The five basic functions of network management are: 1.Fault management 2.Configuration management 3.Performance management 4.Security Management 5.Accounting Management
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