Communications & Networks National 4 & 5 Computing Science

We will learn : –What is a Network –Local Area Networks –Wide Area Networks –Connecting Networks Lesson Objectives

What is a Network? A series of computers linked together so they can send and receive data. We use them for sending s, 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) 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)

Connecting a LAN Stations can be connected by cables or wireless technology Cables: Uses electrical signals to transmit data Cheap but can get interference –Optical fibre Uses light beams to transmit data Expensive but doesn't get interference

Connecting a LAN Wireless –Infrared communication Like the TV controls –Bluetooth Range of about 10 metres –WIFI ( Wireless Fidelity Alliance) Range of about metres – popular for home use and public places 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.

Connecting a WAN Telecommunications links –The communication of information over a distance using: Microwave transmission Satellite links

Network Security Security methods include: –Passwords & user IDs –Encryption –Firewalls –Physical methods – eg locks

We will learn about: –Network Interface Cards –Social, Legal & Ethical Issues Lesson Objectives

Recap - LAN Area: Room, building or group of buildings Stations & File Server Connecting LAN: –Copper cable (Cat 5) –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

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

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 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

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 s. 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 Objectives

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 –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 client –Program for sending and receiving

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: – – Hyperlinks are used to ‘travel’ around the web

The Web - HTML Title of the document The body of the document H yper T ext M ark-up L anguage 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 Objectives

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

Client/Server and Peer to Peer National 4/5 Computing Science

Lesson aims By the end of this lesson you will be able to:  Describe what a peer to peer network is  Describe what a client server network is  Discuss the differences between them

Client and Server Networks You are working on a client and server network Your machine is a CLIENT Your documents are stored and internet access is managed through the schools SERVER You connect to a server to use its resources This can vary depending on the server Might just be to store files…

A sample Client Server network Client Server File Server Web Server

What can a server do? Servers can perform multiple roles – some are –They can run servers –They can store files and control access rights to files –Control Internet Access –Host Web Sites –Control printing for multiple computers

Peer to Peer Networks You can run a peer to peer network A peer to peer network is where each computer shares the functions/files of a network. Peer to peer networks have advantages:  Each computer has its own backing storage so does not rely on an expensive server.  No expensive server hardware or software to purchase  No complex server software to setup

Uses of Peer to Peer Networks Distributed downloading –Where instead of downloading from one central location you download pieces of a file from multiple machines Can be used for legal AND illegal purposes –The technology is legal! –The files being shared may not be!

Comparison Cheap to set up Each user has to take own backups Poor Security Software has to be installed on every machine Doesn’t require a network manager Expensive to set up Centralised backup High security (Usernames and passwords) Software can be installed centrally Requires a network manager Peer to PeerClient Server