4 What is a Computer Network? A computer network consists of two or more computer connected to allow the sharing of expensive peripherals or data.
5 LANs and WANs There are two main types of computer network: A Local Area Network (LAN) is usually in a single office or building.A Wide Area Network (WAN) can be spread over a very large area and usually uses the Public Telephone Network to transfer data.
6 The Internet The Internet is a form of Wide Area Network It is actually a large collection of networks, or a network of networks.Internet
7 Accessing the Internet To access the Internet appropriate hardware, software and an Internet Service Provider (ISP) are usually required.Hardware – computer, modem or cable modem, cabling.Software – Communications software
8 The World Wide WebThe World Wide Web (WWW) is a huge source of information stored on computers all over the world.These computers are called servers.A web browser is used to access web pages.A web browser can also often be used to access and file transfer.
9 What is a Web Page?A web page is a text document formatted using special tags.A web page can include text, graphics, hyperlinks and other multimedia elements.The language used is called Hypertext Markup Language (HTML).Each tag is identified by < > symbols.
10 Mobile Access to the Internet It is possible to gain mobile access to the Internet from some devices such as mobile phones.A special protocol called Wireless Application Protocol (WAP) is used.Mobile devices use software called a microbrowser to access specially formatted web pages.
11 Navigating the WWWIt is possible to navigate between web pages using a number of different methods:Clicking hyperlinksBack and forward arrows in browserEntering URL in address boxUsing search engine
12 The Structure of a Web Address The pathnameThe protocolThe domain name
13 Electronic MailElectronic messages can be transferred around the world using electronic mail.Each user must have an address and access to the Internet.
14 Structure of an email Address Domain nameUser namePronounced “at”
15 File TransferFile transfer allows files such as pictures and executable programs to be transferred electronically.The File Transfer Protocol (ftp) is the most common method of carrying out file transfer.A special program called an ftp client or a browser can be used to transfer files
16 E-commerceThe carrying out of business or providing a service using the Internet.This includes:e-salese-businesse-governmente-marketing
17 Advantages of e-commerce Reducing the costs of premisesSpeed of ordering and dispatching goodsReducing the costs of advertisingAbility to order any time of day or nightReduced cost of goods
18 Implications of e-commerce Possible to work from homeFast ordering and delivery of goodsSharing information
19 Converging Technology Devices which incorporate networking technologyIncludes:Digital televisionMobile phonesMobile Internet accessHome security systemsCentral heatingWireless peripherals
20 The Regulation of Investigatory Powers Act 2002 Allows authorities to access encrypted electronic mail messagesaccess allowed ifIn the interests of national securityFor the prevention or detection of crimeIn the interests of the economic well being of the country
21 Code of Conduct Protect against inappropriate use of the Internet at School – reduce access of inappropriate materialHome – alleviate parental worries
23 Physical SecurityRestrict access to a computer which is connected to a network bykeeping it in a locked room.Providing a lock on the keyboard or power switch.
24 Software SecurityTo restrict users access to a network they should always have to log on using a unique user name and password.Passwords should be changed regularly.
25 Data Encryption Electronic mail is not private. To make message more secure data can be scrambled using special softwareA “key” is used to encrypt and encrypt and decrypt the message
26 Filtering ContentTo reduce access to inappropriate material schools and organisation often use filtering software to “block” web pages and messages containing banned words.
27 Potential Network Threats Hardware failure – hardware devices must be maintained properlySoftware failure – software on server can crashData transmission failure – electrical interference, problems with cablesPhysical disasters
28 Backup StrategyA backup copy should always be kept in a safe place in case the original is lost or damaged.Backup copies should be made regularly.
31 Types of TransmissionUnicast – data sent by one computer to one other computer.Multicast – data sent by one computer to a specified group of others.Broadcast – data sent by one computer which can be accessed by any other.
32 Voice and Data Transmission Voice and computer communications often take place over the same network cables.This reduces costs of networking for a Local Area Network.The Public Telephone Network is the basis for Wide Area Networks
33 Wireless Communication It is possible to set up networks without any wires at all.Wireless Personal Area Network (WPAN)Wireless Local Area Network (WLAN)Wireless Wide Area Network (WWAN)
34 Connecting to the Internet Dialup – slow access using a modemADSL – Asynchronous Digital Subscriber Line to provide broadband accessISDN – Integrated Services Digital Network provides faster than dialup accessCable Modem – used to connect to cable television network to provide broadband accessLeased Line - a dedicated telephone that is only used by the organisation paying for it
35 BroadbandA connection to the Internet which is “always on” and provides fast access is known as broadband.ADSL and cable are two examples of broadband access to the Internet.
37 Domain NamesThis identifies the organisation which stores the web pageA number of Top Level Domains (TLD) provide information about the type of organisation:.com,.gov,.sch,etc
38 Domain Name ServiceThe Domain Name Service (DNS) is responsible for taking the URL entered by the user and transforming it into the appropriate IP address.The IP address is a series of 4 numbers, for example: