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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 – Encryption – Physical methods Communications & Networks Standard Grade Revision: Electronic Communications Networks (Recap) LAN WAN Security on Networks 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 • File Transfer – Files can be attached – Size limit – Attached viruses • Disadvantages: – Spam – Viruses – Lack of Netiquette 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 Standard Grade Revision: The Internet E-Communications (Recap) E-Mail Text Messaging Netiquette The Internet • A Wide Area Network across the world • The network of networks – Lots of smaller networks joined together 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 • 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 • Hyper links are used to ‘travel’ around the web The Web - HTML • Hyper Text Mark-up Language • The language used to write web pages <"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> Search Engine • Special web site to help you find information • A big database! • Some of the main search engines:
