Communications & Networks Intermediate 2 Computing (Systems Unit)

Communications & Networks

Intermediate 2 Computing(Systems Unit)

What is a Network?

• A series of computers linked together so can send and receive data.

• We use them for sending e-mails, downloading files, shopping, etc

• They are divided into two types:– Local Area Network

(LAN)– Wide Area Network

(WAN)

Local Area Network (LAN)• Cover a small area such as one room or

building.– The school has a LAN

• Each computer on a LAN is called a station

• One station is called the file server. – The file server is where

all the data & files are kept

Advantages of a LAN

• Share data• Share peripherals (resource sharing)• E-mail• Passwords keep data secure• Different levels of access

– stop unauthorised access

• Flexible access– Use any station connected to the LAN

• Many users can use same document at the same time (workgroup computing)

Transmission media for LAN• Stations can be connected by cables or

wireless technology• Cables:

–Unshielded Twisted Pair of copper wire (UTP)

• Uses electrical signals to transmit data• Cheaper but can get interference

–Optical fibre • Uses light beams to transmit data• Expensive but doesn't get interference

Transmission media for LAN

• Wireless– Infrared communication

• Like the TV controls

– Bluetooth• Range of about 10 metres

– WIFI (Wireless Fidelity Alliance)

• Range of about 12-50 metres

Bluetooth & WIFI use radio waves

Wide Area Networks (WAN)• Connect computers across large distances

• Spread across countries & cities worldwide using telecommunications links

• Similar advantages to LAN but on a bigger scale.

Transmission Media for WANs

• Telecommunications links– The communication of information over a

distance using:• Microwave transmission• Satellite links

Network Security

• Security methods include:– Passwords & user IDs– Encryption– Physical methods

• We will learn about:

– Client Server Networks

– Network Interface Cards

– Multi-Access Computers

– Social, Legal & Ethical Issues

Lesson Objectives

Recap - LAN

• Area: Room, building or group of buildings

• Stations & File Server• Transmission Medium:

– Copper cable– Fibre optics– wireless

• Advantages of LANs– Share data– Resource sharing– Different levels of

access – Flexible access– workgroup computing

Recap - WAN

• Area: town, city,world

• Transmission Medium:– Telecommunications

Links• Satellites• Microwave transmission

• Network Security:– Passwords & user IDs– Encryption– Physical methods

Client & Server Networks

• A method of network organisation• Each workstation is called a client• Each workstation is connected to a central

system called a server• The server can be used for:

– Holding all the data files and application software

– Organising printing on the network– Organising the clients’ access to the internet

ServerClient

Printer

ClientClientClient

Client / Server Network

Network Interface Card

• Allows the computer system to communicate with the network

• Every device that is connected to the LAN will need a NIC, for example, computer, printer and scanner.

• It take the data sent by your computer– stores it in its own memory

locations, – then adapts it ensuring it

follows the communication rules

Multi-Access Computers• Enable many users to:

– Access the system at the same time– Share the proccessing power of the system– Share the available memory– Share the data on backing storage

• The terminals attached to these computers useually have no processing power of their own.

• The terminals would be made up of just a monitor and keyboard

Multi user computer

Mainframe Computer

Printer

Multiuser Computer

TerminalTerminal

Terminal

Terminal

Social Issues

• Teleworking– Process of using a WAN to work from home

• WANs can improve communications for people in remote areas

• Some people can’t afford the cost so a gap could form between the “Information Rich” and the “Information Poor”

• Some people believe that computers cause social isolation

Legal & Ethical Issues

• Legal:– Computer Misuse Act– Copyright, Designs & Patents Act– Data Protection Act

• Ethical:– Invasion of personal privacy– Censorship & freedom of speech

Communications & Networks

Electronic Communications

Lesson Objectives

•Electronic Communication•Text/Instant Messaging•E-Mail

•Advantages & Disadvantages•File Attachments

•Netiquette

Electronic Communication

• The process of sending and receiving electronic messages.

• Electronic messages include:– Electronic mail– Text messaging– File transfer (attachments)

Text Messaging

• Types:– Short text message.– Instant messaging.

• Language used:– Casual/Informal– Abbreviations– Acronyms

E-mail

• Advantages:– Fast compared to post– Cheap – ISP connection only– Web mail – access anywhere– Send multiple copies (CC)– Organise folders

• Disadvantages:– Spam– Viruses– Lack of Netiquette

• File Transfer– Files can be attached– Size limit– Attached viruses

Netiquette

• DON’T WRITE IN CAPS!• Don’t leave the Subject Field blank• Don’t over use Formatting• Don’t give out personal details• Don’t start Flame Wars (Trolling)• Use proper English in e-mails.• Don’t send dumb jokes, chain mail, etc

• Code of conduct used in e-communications

Communications & Networks

The Internet

• Internet Services• Accessing the

Internet • The World Wide

Web• Search Engines

Lesson Objective

s

The Internet

• Enables computers and networks worldwide to connect with each other

• The network of networks

Internet Services

• World Wide Web (www or just web)– Used for browsing or searching

• E-mail– Communication & exchange of information

• File transfer– Sending & receiving large

amounts of information

Accessing the Internet

• Internet ready computer• Internet Service Provider (ISP)

– A company that provides access to the internet

• Browser– Software used to view web pages

• Email client– Program for sending and receiving email

Accessing the Internet

• Dial-Up– Uses a modem and an ordinary

phone line to dial up the number of your ISP that connects you to the internet.

• Broadband– Uses either a digital subscriber line

(DSL) or a cable modem

• Modem– The telephone line doesn’t understand binary– A modem is needed to translate for the computer

World Wide Web

• Information is stored in web pages on web sites

• These pages can be viewed in a browser

• They are found by an address such as:– www.google.co.uk – www.msn.com

• Hyperlinks are used to ‘travel’ around the web

The Web - HTML

<"http://www.w3.org/TR/html4/loose.dtd"><html><head>

<meta name="Description" content="Your description"> <meta name="Keywords" content="first, second, third"> <title>Title of the document</title> <base href="http://www.yourdomainname.com/images/"></head> <body> The body of the document</body></html>

• Hyper Text Mark-up Language

• The language used to write web pages

Search Engine

• Special web site to help you find information

• A big database!

• Some of the main search engines:

• Software on the internet

• Video conferencing• Streaming media• Internet services• Mobile Internet

Lesson Objective

s

Software on the Internet

• Freeware– Free software but the author still holds the

copyright– You are not allowed to change it

• Shareware– 30-Day trial period– After that either pay for it or delete it

Software on the Internet

• Commercial– Pay full price up front– Limited to one backup copy– Licence agreements are very detailed

Video Conferencing

• Using networks to send audio and visual data.

• Enables people to have face-to-face meetings

• Saves time and money

• No need to travel long distances for business

Video\Audio Streaming

• The internet is used to send data one way

• Online radio stations do this

• Uses large amount of network bandwidth

Other Internet Services

• Chat & instant messaging– Text based communication– Communication is in real time (instant)

• Weblogging (Blogs)– A type of online diary– Used for both business & personal

• Bulletin boards– Electronic notice board

Mobile Internet

• Using the internet while on the move– Walk ‘N’ Surf

• Devices include– Mobile phones, Laptops, palmtops, pdas