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Chapter 9

Networking and

Telecommunication

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Topics

Linking Up: Network Basics

Electronic Mail, Teleconferences, and Instant Messages: Interpersonal Computing

Converging Communication Technologies: From Messages to Money

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Linking Up: Network Basics

A computer network is any system of two or more computers that are linked together.

How do networks impact systems? People share computer hardware, thus reducing costs People share data and software programs, thus

increasing efficiency and production People work together in ways that are otherwise

difficult or impossible

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Basic Network Anatomy

The three basic components of a network: Hardware Software People

Direct Connection--one of many computers linked in an office

Remote Access--computer linked to a network through a phone line, television cable system or satellite link

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The Network Interface

A network interface card (NIC) permits direct network connection

It adds an additional serial port to the computer

The network interface card controls the flow of data between the computer’s RAM and the network cable.

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Communication á la Modem

A modem is a hardware device that connects a computer’s serial port to a telephone line (for remote access).

May be internal on the system board or external modem sitting in a box linked to a serial port.

Modem transmission speed is measured in bits per second (bps) and generally transmit at 28,000 bps to 56.6K bps

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Conversion of Signals

aa

Terminal

Modem

Modem

Analogsignals

Phone line

Digitalsignals

Digitalsignals

Computer

Computers send digital signals. The modem (modulator/demodulator) converts the digital signals to analog so that the message can be transmitted through telephone lines.

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Conversion of Signals

aa

Terminal

Modem

Modem

Analogsignals

Phone line

Digitalsignals

Digitalsignals

Computer

The modem (modulator/demodulator) converts the analog signals back to digital signals that are understood by the computer

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Faster Modem Alternatives:Broadband Technologies

DSL - Digital Subscriber Line Uses standard phone lines Makes use of unused frequencies in phone lines Speed dependent on distance from main office

Cable Modems Uses cable television networks Makes use of unused channel frequencies Speed dependent on number of users on network at a

given time

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Networks Near and Far

Local-area network (LAN) Computers are linked within a

building or cluster of buildings.

Each computer and peripheral is an individual node on the network.

Nodes are connected by cables which may be either twisted pair (copper wires) or coaxial cable.

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Networks Near and Far

Wide-area network (WAN)

A network that extends over a long distance.

Each network site is a node on the network.

Data transmitted over common pathways called a backbone.

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Wide-Area Networks

Made up of LANs linked by phone lines, microwave towers, and communication satellites.

Bridges, routers, and gateways are hardware devices that pass messages between networks.

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Communication Software

Protocol - set of rules for the exchange of data between a terminal and a computer or between two computers

Communication software establishes a protocol that is followed by the computer’s hardware

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Communication Software

Many forms: Network operating system (NOS) - handles

communications between many workstations

Client/server model - one or more computers act as dedicated serves and all the remaining computers act as clients

Peer-to-peer model - every computer on the network is both client and server

Many networks are hybrids, using features of the client/server and peer-to-peer models

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Client/Server Model

Client software sends requests from the user to the server

Server software responds to client requests by providing data

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The Network Advantage

Why do people use networks?

To share computer resources (hardware and software)

To support working together in new and different ways

Lotus Notes is a groupware application that facilitates information sharing and

workgroup collaboration.

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E-mail Mail, Teleconferences, and IM: Interpersonal Computing

Electronic mail, teleconferencing and instant messaging allow communications between two or more people.

Meetings can be held in real-time (synchronous) or delayed (asynchronous)

Chat rooms are examples of synchronous communications; bulletin boards are examples of asynchronous communications.

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The Postal Alternative

E-mail is fast.

E-mail doesn’t depend on location.

E-mail facilitates group communication.

E-mail messages are digital data that can be edited and combined with other computer-generated documents.

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Advantages of E-mail and Teleconferencing

On-line communication is less intrusive.

On-line communication allows time shifting.

Teleconferences and e-mail promotes teleworking.

Teleconferences and e-mail emphasize the message over the messenger.

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On-line Issues for E-mail and Teleconferencing

Vulnerable to machine failures, network glitches, human errors and security

Threat to privacy

E-mail forgery

Information overload

Missing “human” elements of communication

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Converging Communication Technologies: From Messages to Money

On-line Information Services

Fax Machines and Fax Modem

Voice Mail and Computer Telephony

Global Positioning System

Video Teleconferencing

E-Money

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Physical Media for Networks

Networks are built on physical media. Twisted pair (Category 5) Twisted pair (Traditional) Coaxial Cable Fiber optic Wireless/infrared Wireless/radio

What affects network performance? Bandwidth and maximum operating distance

“Never in history has

distance meant less.”

Alvin Toffler

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Bandwidth

The amount of information that can be transmitted in a given amount of time

Impacted by: Physical media that make up the network Amount of network traffic Software protocols of the network Type of network connection

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Fiber Optic Cables

Fiber optic cables are replacing aging cooper lines with high-capacity fiber optic cables.

They use light waves to carry information at blinding speeds.

A single fiber optic cable can transmit half a gigabit (500 million bits) per second, replacing 10,000 standard telephone cables.

Data is transmitted more accurately and reliably.

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Digital Communication Comes Home

Digital communication lines will radically change services to our homes.

Multi-person video phone conversations, universal e-mail, customized digital newspapers, automatic utility metering and unlimited entertainment options

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