Lesson 7Networks

Unit 1—Computer Basics

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Objectives

Describe the benefits and disadvantages of networks.

List and describe the types of networks.List and describe communications hardware.List and describe communications media.Describe the different network topologies.Describe network architecture and protocols.

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Introducing Networks

A network is a group of two or more computers linked together. Most networks have a server that manages

the network resources. Most networks have multiple clients, which

are computers that access the server.

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Introducing Networks (cont.)

A network confined to a limited geographical area is called a local area network (LAN).

A network spread over a wide area is called a wide area network (WAN).

The transmission of data from one location to another is called data communications.

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Network Building Blocks

Sending data from one computer to another requires a channel, the link through which the message is sent. A phone line or cable is a channel.

A device on each end of the channel converts the computer signal to a signal type that the channel can send/receive.

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Network Building Blocks (cont.)

Sending a message through the channel requires a transmission media, which can be physical or wireless.

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Network Building Blocks (cont.)

This figure shows the main components required for data communications: a sending device, a receiving device, a communication path or channel, a device to convert the signal so that the channel can carry it, and the soft-ware to send and receive messages.

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Network Benefits

Networks provide almost instant communication with other users on the network. Users can share information. Users can share hardware. Users can share software. Users can work on group projects.

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Network Disadvantages

Data security and unauthorized access are disadvantages of a network.

Other disadvantages are Malicious code Network faults Setup and management costs

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Types of Networks

Two of the more common types of networks Local area networks (LANs) Wide area networks (WANs)

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Local Area Networks

Local area networks usually are confined to a limited area. The two most popular LANs are

Client/serverPeer-to-peer

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Client/Server vs. Peer-to-Peer

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Wide Area Networks

Wide area networks are spread across a city, a state, the country, or the world. Most WANs consist of two or more LANs

connected by routers. Some WANs may be configured as intranets

or extranets.

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Other Types of Networks

Metropolitan area network (MAN)Neighborhood area network (NAN)Personal area network (PAN)Home area network (HAN)Campus area network (CAN)

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Network Hardware

Most networks consist of a server and multiple client computers.

They also include two other categories of hardware: communications hardware and network transmission hardware.

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Network Hardware (cont.)

Communications hardware These devices facilitate the transmitting and

receiving of data.Network transmission hardware

These devices connect the cabling and amplify.

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Communications Hardware

Modems: Convert analog signals to digital and vice versa Dial-up modems enable a computer to send

data over a standard phone line.The sending computer and the receiving

computer must both have modems.

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Communications Hardware (cont.)

Modems (cont.) Cable modems use coaxial cable to send

data over cable TV lines.These have much faster transmission rates

than a standard telephone line modem. DSL and ISDN modems use telephone lines.

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Communications Hardware (cont.)

Network interface cards (NICs) All PCs in a LAN must have a NIC.

Gateway Links networks using different protocols

Router Connects multiple networks and determines

the fastest route for sending data over the network

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Communications Hardware (cont.)

Wireless access point Connects wireless communication devices

Hub Receives and sends signals back out

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Communications Media

Physical media types Twisted-pair cable Coaxial cable Fiber-optic cable

Wireless media types Radio signals Microwaves Satellites

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Communications Media (cont.)

Twisted pair

Coaxial

Fiber-optic

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Wireless Media

Microwaves

Satellites

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Other Communications Media

IrDA Infrared transmission Requires line of site

Bluetooth Uses radio waves Short distance transmission of about 30 feet

WI-FI Wireless fidelity; wireless transmission

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Bluetooth Technology

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Network Topologies

A topology is the geometric arrangement of the network.

The most common topologies are Bus: All devices are connected to a master

cable. Ring: Similar to a bus except that the

devices are connected in a circle Star: All devices are connected to a central

hub or computer.

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Bus Topology

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Ring Topology

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Star Topology

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Communications Protocols

A protocol is a set of rules that allows computers to exchange data. The protocol determines

How a sending device indicates it has finished sending

How a receiving device indicates the message was received

The type of error-checking to use

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Communications Protocols (cont.)

The most common protocols are Ethernet: Most common LAN protocol Token ring: Also used on LANs TCP/IP: Used on the Internet

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Network Operating Systems Software

Networks require a network operating system (NOS) and a desktop operating system. The clients run the desktop OS.

The NOS runs on the server and providesNetwork administration toolsPrint servicesClient servicesSecurity services

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Summary

Data communication is the transmission of data from one location to another.

A network is a group of two or more computers linked together.

The Internet is the biggest network of all.Networks have advantages and

disadvantages.

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Summary (cont.)

A local area network generally is confined to a limited geographical area.

A wide area network is made up of several connected local area networks.

The two popular types of LANs are the client/server network and peer-to-peer network.

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Summary (cont.)

Other types of specialized networks include metropolitan area networks (MANs), neighborhood area networks (NANs), personal area networks (PANs), home area networks (HANs), and campus area networks (CANs).

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Summary (cont.)

You can use a network for information sharing, hardware sharing, software sharing, and as a collaborative environment.

The link through which data is transmitted is the communications channel.

Transmission media can be either physical or wireless.

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Summary (cont.)

Physical media includes twisted-pair cable, coaxial cable, and fiber-optic cable.

Wireless media includes radio signals, microwaves, and satellites.

Most networks consist of a network server and computer clients.

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Summary (cont.)

Communication devices facilitate the transmitting and receiving of data, instructions, and information.

Communication devices include dial-up and cable modems, DSL and ISDN modems, network interface cards, gateways, routers, wireless access points, and hubs.

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Summary (cont.)

Network interface cards enable the sending and receiving of data between the PCs in a network.

A router directs the Internet or network traffic.

Physical media includes twisted-pair cable, coaxial cable, and fiber-optic cable.

Wireless media includes microwaves, satellites, IrDA, Bluetooth, and Wi-Fi.

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Summary (cont.)

Network topologies include bus, ring, and star.

A protocol is an agreed on set of rules and procedures for transmitting data between two or more devices.

The Ethernet protocol is one of the most popular LAN protocols.

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Summary (cont.)

Token ring is the second most widely used LAN protocol.

TCP/IP is a protocol used by both LANs and WANs to connect to the Internet.

All computers on a network require an operating system, and networks require network operating systems.