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Networks

• A network is a collection of computers and devices connected together via communications devices and transmission media

• Advantages of a network include:

Facilitating communications

Sharing hardware

Sharing data and information

Sharing software

Transferring funds

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Bandwidth

• Measurement of the capacity of the channel• Categories – Voiceband also known as low bandwidth– Medium band – Broadband• Used for high capacity transmission• Used by DSL, cable, and satellite

Protocols

• Set of communication rules• Standard for Internet: TCP/IP (Transmission

control protocol/Internet protocol)– Identification – Reformatting

Network Classifications

• Local area networks (LAN)• Home networks

– WLAN (Wireless LAN)• Metropolitan area networks (MAN)• Wide area networks (WAN)

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Network Classifications

• A local area network (LAN) is a network that connects computers and devices in a limited geographical area

• A wireless LAN (WLAN) is a LAN that uses no physical wires

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Network Classifications

• A metropolitan area network (MAN) connects LANs in a metropolitan area

• A wide area network (WAN) is a network that covers a large geographical area

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Network Architecture

• The design of computers, devices, and media on a network is sometimes called the network architecture

Client/server Peer-to-peer

Terminal

Peer-to-peer (P2P) Model

Client

Server

Client

Client Client

Client/Server Model

Peer Peer

Server must be prepared to serve multiple clients at any time.

Peers communicate as equals on a one-to-one basis.

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The Client/Server Model• When processes need to communicate:

• Examples:– file server– mail server– web server =>

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The Client/Server Model (continued)• Client & server have strictly defined roles:

– client sends request – then waits for answer– server accepts request – processes & returns answer

• Protocols, defining how to:– encode messages– address messages– handle sending and

receiving

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• Protocols: Example• http, ftp

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The Peer-to-peer Model

• P2P describes an Internet network on which users access each other’s hard disks and exchange files directly over the Internet

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Network Topology

• A network topology refers to the layout of the computers and devices in a communications network

Star network Bus network Ring network

Network Topology

• Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer.

• Types of network topology– Star– Bus– Ring– Hierarchical

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Star Network

• Smaller computers linked to a central unit

• Central unit is called the network hub

• Control is maintained by polling

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Bus Network • Each device handles its own communication control• There is no host computer• Has a common connecting cable called a backbone

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Ring Network

• Each device is connected to two other devices

• No central file server or computer

• Useful in a decentralized environment

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Hierarchical Network

• Several computers linked to a central host

• Computers are hosts to other computers

• Useful in centralized organizations

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Principal Network Configurations

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Network Communications Standards

Ethernet Token ring TCP/IP Wi-Fi

Bluetooth UWB IrDA RFID

WiMAX WAP

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Network Communications Standards

Ethernet is a network standard that specifies no computer controls when data can be transmitted

The token ring standard specifies that computers and devices on the network share or pass a special signal (token)

TCP/IP is a network standard that defines how messages are routed from one end of a network to another

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Network Communications Standards

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Network Communications Standards

• Wi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication

• Sometimes referred to as wireless Ethernet

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Network Communications Standards

• Bluetooth defines how two Bluetooth devices use short-range radio waves to transmit data

• UWB (ultra-wideband) specifies how two UWB devices use short-range radio waves to communicate at high speeds

• IrDA transmits data wirelessly via infrared (IR) light waves• RFID uses radio signals to communicate with a tag placed in

or attached to an object, animal, or person

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Network Communications Standards

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Network Communications Standards

WiMAX (802.16)

• Developed by IEEE• Towers can cover a 30-mile

radius• Two types are fixed

wireless and mobile wireless

• Provides wireless broadband Internet access

Wireless Application Protocol (WAP)

• Specifies how some mobile devices can display the content of Internet services• Web• E-mail• Chat rooms

• Uses a client/server network

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Communications Software

• Communications software consists of programs that:

Help users establish a connection to

another computer or network

Manage the transmission of

data, instructions, and information

Provide an interface for users to communicate with one another

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Communications Over the Telephone Network

• The public switched telephone network (PSTN) is the worldwide telephone system

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Communications Over the Telephone Network

Dial-up lines

Dedicated line ISDN line

DSL FTTP T-carrier line

ATM

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Communications Over the Telephone Network

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Communications Over the Telephone Network

• ADSL connections transmit data downstream at a much faster rate than upstream

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Home Networks

• Home networks provide computers with the following capabilities:

Connect to the Internet at the

same time

Share a single high-speed Internet

connection

Access files and programs on other

computersShare peripherals

Play multiplayer games

Connect game consoles to the

Internet

Subscribe to and use VoIP

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Home Networks

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Organizational Internets• Intranets– Private network within an organization– Provides information to employees

• Extranets– Private network that connects

organizations– Used to allow suppliers and others

access

• Firewalls– Security system – Protects against external threats

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Careers In IT

• Network Administrator– Manage a company’s LAN and

WAN networks– Maintain hardware and

software– Diagnose and repair problems– Candidates usually have a

bachelor’s degree in computer science and practical experience

– Annual salary is typically between $43,000 and $68,000