Communications Networks Standard Grade Revision Networks

Communications & Networks Standard Grade Revision: Networks

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 • Optical Fibre

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

Lesson Objectives • We will learn about: – Client Server Networks – Network Interface Cards – Multi-Access Computers – Social, Legal & Ethical Issues

Recap - LAN • Area: • Stations & File Server • Transmission Medium: • Advantages of LANs – Share data – Resource sharing – Different levels of access – Flexible access – workgroup computing

Recap - WAN • Area: • Network Security: • Transmission Medium: – Telecommunications Links

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

Client / Server Network Client Printer Client Server

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 – Shave 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

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 • Code of conduct used in e-communications • • 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

Communications & Networks The Internet

Lesson Objectives • Internet Services • Accessing the Internet • The World Wide Web • Search Engines

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

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 • Hyper Text Mark-up Language • The language used to write web pages <"http: //www. w 3. org/TR/html 4/loose. dtd"> The body of the document

Search Engine • Special web site to help you find information • A big database! • Some of the main search engines:

Lesson Objectives • Software on the internet • Video conferencing • Streaming media • Internet services • Mobile Internet

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

VideoAudio 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 (Blog) – 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