SAMPLE PAGES. Unit 12.1 Information and Communication Systems Topic 2: Networking. What is a network? Network node

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1 Topic 2 focuses on networking. It covers: Definition of a network. Characteristics and functions of network devices. Specification of local area network (LAN). Network software. Application software. Basic LAN setup. Unit 12.1 Information and Communication Systems Topic 2: Networking What is a network? A computer network consists of two or more computers linked together to enable the use of shared resources such as printers, storage, software and the exchange of files. The devices on the network can be linked by cable, telephone lines, or a range of wireless devices. Computer networks use devices such as hubs, switches and routers to connect the various computers together and to transmit the signals. A computer network allows users to: Work on a file that is on another computer. Print a document on a printer connected to a network. Send a message to another user on the network. A computer network can span the whole world or be confined to a single room. A network is made up of: Nodes points that allow the input or output of data (such as printers, scanners, other computers and disk storage devices). Connections or links between the nodes. Computer and network software to allow and manage the connections. Network node A node is a connection point on a network that allows the input or output of data. It can be any device that is connected to the network, such as a: Computer. Printer. Hard disk. Scanner. Another peripheral device.

2 22 Unit 12.1 Information and Communication Systems Network hardware Server A server is a software and hardware package that provides access to particular services. A server may be a dedicated computer that provides a specific service or a single computer that provides a range of services. Providing access to resources and files for many users requires management and control. For example, rules are usually put in place for different users to access different files on a network. Users need to know that their files are safe and protected from unauthorised or unwanted access. Servers that are often used on a network are: File servers these store files for sharing access, storage and backup. They usually have differing levels of permission depending on the owner of the file and the type of file. Print servers these manage files for printing and send them to the appropriate printer. Mail servers these manage the receipt, delivery and storage of mail. Web server this manages web pages and delivers content to legitimate users. Many organisations with networks use client-server as the basis for their local area network. A number of servers can be run on the same computer hardware, acting as virtual servers. What is a network switch? A switch is used to connect devices on a network. A switch controls the connection of the devices so that they can communicate with each other efficiently and effectively. A switch processes and sends data from one device to another on a network. Switches are used to create networks. An unmanaged switch is one that works out of the box it does not need to be configured by a user or technician. It does not need to be configured when it is connected to a network. However, unmanaged switches have less capacity than a managed switch. An unmanaged switch is useful in a small network such as one used at home. A managed network switch is configured by the user and is required for larger and more complex networks. The switch is set up and monitored by a network engineer. A managed switch provides greater network control and capacity than an unmanaged switch. Switches are generally a major financial investment in corporate and government networks. Their capacities, features and functions vary greatly. For example, the number of ethernet ports that connect to a switch varies greatly. Some of the switches support redundant power supplies to enhance their reliability. Cisco and Hewlett-Packard are two well-known companies that develop and market network switches. What is a network hub? A Cisco Catalyst 3650 Series switch A network hub is a device that allows multiple ethernet devices to be connected together. A signal can come into a hub and be distributed to a number of devices on the network.

3 Topic 2: Networking 23 A hub does not manage the traffic on a network; it typically broadcasts its signal to all the ports on the hub. What is a router? A router is a hardware device that is used to connect networks. A router links computers to the Internet so users can share the connection. A router chooses the best path for information to travel so it is received quickly. Home networks will often have a router built into a network modem that will allow a number of users to connect to the Internet. A router can transmit data using different media including coaxial cable, CAT 5 cable, fibre optical cable and wireless. A router Client server The best example of client and server is a web server and a client computer with a web browser. An HTTP (hypertext transfer protocol) request from the browser over the network to the web server is met when the server sends the HTML page and associated files to the client computer. The browser can read the HTML instructions and content and render the contents. Most networks have proxy servers that sit between the client (person who requests server access) and the server on the World Wide Web. When the client requests access, the request goes to the proxy server, which then determines whether access can be granted according to its filters. These usually sit inside the firewall and frequently accessed content may reside there. The practical effect is that the user does not distinguish if the content was delivered from the actual or the proxy server. Intranets (a local network set using internet protocols) operate using a server within the organisation. With appropriate security (such as user names and passwords with secure tunnelling) such as a VPN (virtual private network) the intranet can be accessed from the Internet, with a client server relationship. Peer-to-peer network A peer-to-peer network is where all computers on a network can share files and resources with each other. Networks such as these are mostly used in homes or in small organisations. The extent to which the files on a computer can be shared depends on setting appropriate permissions for access. There can be delays in file sharing as requests are made and files are sent from a computer. Peer-to-peer could be suitable for a small home network and for file sharing over the Internet. Internet peer-to-peer file sharing enables files to be transferred with suitable software. There are security issues with this practice as malware can be easily accessed and open a computer to hackers and viruses.

4 24 Unit 12.1 Information and Communication Systems System software Information systems within organisations could be employed on a variety of computer hardware using a variety of operating systems. Operating system software is created by companies to operate using particular computer chips. Most software companies do not make the computer hardware the software will operate on, although some companies such as Apple sell their hardware and operating system as an integrated package. Microsoft offers Surface tablets that include an integrated package. Most systems administrators will endeavour to implement a Standard Operating Environment (SOE) that will specify the particular operating system that is to be used throughout the organisation. Compatibility needs to be maintained between the operating system and: Computer hardware. Peripheral devices. Application software. Utility software. When software upgrades occur, compatibility needs to be reassessed and tested to ensure that, if the upgrade is made, compatibility is maintained and the information system is not interrupted. Organisations often do not engage an upgrade process until compatibility issues are fully examined. Specification of local area network (LAN) Network topology refers to the layout of a network. It represents how the various nodes of a network are connected to each other and how they communicate with each other. Design topology of LAN (star, bus, ring) Star topology In a star topology, all the network nodes are connected to a central computer called the hub. All the nodes on the computer communicate by passing through the hub that controls the network traffic. Bus topology Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone, functions as a shared communication medium that devices attach or Star topology tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

5 Topic 2: Networking 25 Ethernet bus topologies are relatively easy to install and do not require much cabling compared to the alternatives. 10Base-2 ( ThinNet ) and 10Base-5 ( ThickNet ) both were popular ethernet cabling options many years ago for bus topologies. However, bus networks work best with a limited number of devices. If more Bus topology than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable. Ring topology In a ring network, every device has exactly two neighbours for communication purposes. All messages travel through a ring in the same direction (either clockwise or anticlockwise). A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses. Network software Network operating systems Ring topology A network operating system, often abbreviated to NOS, is specialised software that is designed to enhance an operating system by adding networking features. Examples of such software are Microsoft Windows Server, Novell Netware and LANtastic from Artisoft. Firewall A firewall is a system that protects a computer system or network from unauthorised access. On a network, a firewall is made up of: Hardware. Software.

6 26 Unit 12.1 Information and Communication Systems Large companies such as Cisco and Norton typically provide firewalls for networks in organisations. Every message that enters or leaves a network must pass through the firewall. The firewall blocks those messages that do not meet the security requirements. Firewall products often include logging and reporting of perceived attacks. The following illustration shows how a firewall works. Cisco security devices that are used for a firewall on a corporate network How a firewall works Personal firewall Windows includes a personal firewall that is set up to block requests to connect to a computer. This firewall is an application that is accessed via the Control Panel. Device and utility drivers A device driver is a small piece of software that tells the operating system and other software how to communicate with a piece of hardware. For example, each printer comes with a driver that is installed on the computer. The printer driver communicates with the operating system to ensure that information on the screen is printed correctly on the paper in the printer. A utility driver is a program that performs a specific task in the management of computer functions, eg password management, file protection. The utility driver is the software that enables these tasks to be carried out. A printer driver

7 Topic 2: Networking 27 System software operating system Each computer has an operating system. For example, operating systems designed by Microsoft include Windows XP and Windows 7. This software makes the computer usable it provides a link between the hardware and the person using the computer. When the computer is turned on, the operating system starts up the computer. Operating programs are generally purchased with the computer. Some computers are able to use more than one operating system, although only one operating system can run at any one time. The operating system consists of a large range of smaller programs, each of which will have a specific job to carry out. Operating systems are being continually modified and upgraded. For example, Microsoft offers service packs that include updates and security improvements. Application software Application software is a program or a group of programs designed to be operated by end users. These include word processing, spreadsheets and database applications. General-purpose software General-purpose software is used by a range of users. Most people in an organisation will use packages such as Microsoft Office. The actual modules used vary according to the needs of the users. Word processing Word processing software is used to produce, modify, save and print documents. For many years, businesses and organisations used typewriters to create documents. The development of the electronic typewriter provided the first editing facilities, although these were very limited. The first word processing applications were really only text formatting programs. Special codes needed to be entered for each formatting command and it was difficult to insert graphics. The introduction of the graphical user interface and what you see is what you get (WYSIWYG) editing transformed the word processor into a popular and useful application. The ability to see on the screen exactly what a document would look like was a huge advantage. Early word processing programs included MacWrite (on the Apple Macintosh), WordPerfect and Microsoft Word. Microsoft Word is now the most widely used word processing package and it can also be used to produce documents for the Internet. It is generally purchased as part of the Microsoft Office package. Both Microsoft and Google now offer word processing packages online. There is also a range of other free online word Google Docs provides an online word processor. processors available.

8 28 Unit 12.1 Information and Communication Systems Spreadsheets A spreadsheet is made up of a two-dimensional grid of cells arranged in rows and columns. Each cell is defined by its row number and its column number. A cell can contain text, numbers or a formula that displays the results of a calculation. The spreadsheet had its origin in paper-based accounting applications. The paper spreadsheets were used for displaying and calculating financial information. The ability of electronic spreadsheets to immediately re-calculate results once the data was altered made them compelling to use. The first implementation of a spreadsheet on a personal computer was VisiCalc, which was released in 1979 for the Apple II computer. This was one of the first applications on a personal computer that was successful in business. VisiCalc was then developed for a range of other personal computers. The first important spreadsheet application for IBM-based computers was Lotus This became the leading spreadsheet application for DOS-based computers. Microsoft first developed Excel in the 1980s and it was later moved across to a DOS-based application. Excel eventually became part of Microsoft s Office suite of programs and it has become the dominant spreadsheet application. A number of vendors including Microsoft and Google now provide spreadsheet applications online and store the files in the cloud. These applications are available via the Internet. Part of an Excel spreadsheet on the Internet Databases A database is a collection of information that is organised to allow efficient retrieval and reporting of data. Databases were originally collections of printed information arranged in an agreed format. Examples included: Telephone directory. Address book. Dictionary. In the 1960s database management systems were developed for use on computers. The first systems were developed by large companies such as IBM and Oracle. The development of relational database systems in the 1970s, based on the work of Edgar F Codd, led to the dominance of relational database management systems. The first widely used system on personal computer systems was Dbase II, which became very popular on IBM personal computers. Filemaker was another popular database management system, first developed for the Apple Macintosh and later extended to Windows-based computer systems. Microsoft also developed Microsoft Access, which is included in some Microsoft Office packages.

9 Topic 2: Networking 29 Database management packages are of great importance to large organisations. Specialist positions including database administrators (DBA) and systems analysts are need to support the design and implementation of database systems. Part of a Microsoft Access database Desktop publishing Desktop publishing refers to the use of page layout software on a personal computer to produce documents. Page layout software is a tool for designers who create newsletters and magazines to create the documents online. Page layout programs make it easy to integrate text and graphics on the one page. These programs make it easy to manipulate multi-page layouts and to create different layouts. The focus of word processing programs is on the creation and modification of text. Microsoft Word has incorporated some of the features of a desktop publishing package but does not offer the same flexibility in terms of laying out pages and moving elements around. Desktop publishing suddenly became popular in the mid-1980s with the invention of the Apple LaserWriter the first general purpose laser printer and the software PageMaker from a company called Aldus. PageMaker was able to use the what you see is what you get (WYSIWYG) layout of the Apple Macintosh computer to design and lay out pages on the screen. Another important factor was the development of PostScript. This is a programming language invented by Aldus that is a page description language. This optimised pages for printing text and graphics. Publishers were able to lay out documents and proof them accurately using PageMaker and a LaserWriter before sending them to a professional printer for a final production. Apple s LaserWriter was the first PostScript printer.

10 30 Unit 12.1 Information and Communication Systems PageMaker quickly became the de facto standard for page layout programs. Other competitors followed and QuarkXPress became widely used in the industry. Aldus was taken over and PageMaker was replaced by InDesign by Adobe. Microsoft s page layout software is Publisher. Web browsing A web browser is a software program that translates the coding in files on the World Wide Web to render and display text and other media. This allows users to browse the Internet using point-and-click navigation. The programming language used to create web pages is called Hypertext Mark-up Language (HTML). Specialist web programmers use HTML to create and maintain websites. The source code of a website can be viewed: in Microsoft Internet Explorer, this is done by right-clicking within a web page and choosing View Source. Part of the homepage for The National, Part of the HTML code for the homepage of The National The first web browser to be available to the public was called Mosaic and it was released in Following that, Netscape became the most popular browser. Then a new, open source browser named Mozilla became popular and this later evolved into Firefox. Microsoft challenged the browser market with Internet Explorer and this gained a significant share of the market.