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Module 3.1 Networks Overview • • • • • • • What is a network? Reasons for having a network Disadvantages of having a network Components of a network Types of networks Client-server VS Peer-to-peer LAN Network access control What is a network? When two or more computers/devices are connected to each other we have a ‘network’ To share printers, scanners and other devices and files. Reasons for having a network Fast, efficient communication •Make communication among users possible •To enable users to share resources such as information, hardware and software Reasons for having a network Sharing of hardware resources Cutting costs Equipment can be shared amongst many users on the network. Reasons for having a network Centralisation of data • Data is stored centrally for easier access • Data integrity is maintained • Backups are easy to do from one central location Reasons for having a network Transfer of files The files on a CD can be transferred using the network. Reasons for having a network Leisure LAN Parties Reasons for having a network Increased control and security Reasons for having a network Flexible access In a network, users can access their information from any computer on the network Internet banking. Disadvantages of having a network network administrator needed A high level of security needed to keep information confidential Harmful software can spread quickly If the network develops a problem, potentially no users can work, print or access their data. Server crashing can cause a loss of data Components of a network Components of a network • Hardware – Computers and peripherals – Network Interface Controller (NIC) – Switch Switches Fibre cable Components of a network • Communication media – Wired • UTP • Fibre – Wireless • Network operating software Weaknesses of communication media • Attenuation • EMI • Eavesdropping • Crosstalk Weaknesses of communication media Comparison of weaknesses between UTP and Fibre optic cables UTP Attenuation Eavesdropping Electromagnetic interference UTP is susceptible to attenuation therefore the maximum cable length that can be used without having to boost the signal is 100m. UTP is sensitive to eavesdropping although the twisting does help reduce the sensitivity. UTP is sensitive to EMI and power surges although the twisting does help reduce the sensitivity. Fibre optic Fibre has much lower attenuation than UTP. It can transmit over distances measured in kilometres. Fibre is immune to eavesdropping. If the signal was tapped, the flow of light would be broken and the tapping would be detected. Fibre is not affected by electromagnetic interference and power surges. It can be used in areas such as factories and oil refineries where electromagnetic fields can affect communication. Fibre optic cables Types of networks Local Area Networks Wide Area Networks Types of networks • WLAN • Intranet • Extranet Activity Activity1 Written Client-server VS Peer-to-Peer Clients Clients are computers (PCs or workstations) that use but do not provide network resources. They rely on servers for resources such as files and printing. Servers Servers are computers that only provide network resources. They are powerful computers with large hard drives and are never used as normal users' PCs. Peers Peers are those computers that both use and provide network resources. Client-server LAN • Network resources are managed by the server • Used for large networks • High level of security Peer-to-peer LAN • Network resources are shared amongst the computers • Home or very small network • Printers, Internet access and files can be shared Peer-to-peer All computers are peers (equals) and perform the same communication functions. No server is necessary. Client server Each computer in the network is either a client or a server. A server is required. All the computers have high specifications The rest of the computers in the network do not have to have a large disk capacity and can have a less powerful processor. Can only be used with a small number of More suitable for a larger number of computers. computers. Can be installed by a person with reasonably low technical skills Has to be installed by a person with high technical skills Can have a slow performance. Faster performance. Access control when logging into a network • Network security refers to policies put in place to ensure the security of a network by preventing unauthorised access and misuse of the computer network. • Username and password is used to control access to a network • Security and confidentiality of data is important Example of folder permissions Rules to follow for a ‘strong’ password • At least 8 characters long. • Contains a mixture of upper and lowercase letter, numbers and special characters. • Do not use your name, you girlfriend or boyfriend’s name, your pet’s name or anything else that is easy to guess about you. • Change your password at least every 2 months. • Passwords should not follow a pattern such as asdf. • Be creative! • The following would be an example of a ‘good’, secure password: q&F1oP%*>41z How do you know that you are connected to a network? Presence of extra (logical / shared) drives How do you know that you are connected to a network? • Presence of other computers in “My Network Places”. • Access to devices such as printers not directly attached to the computer is possible. • Indicator showing network activity in the system tray. Activity Activity2 Written Glossary Clients Clientserver network E-mail servers Extranet Internet or proxy server Intranet Network NIC Network operating system Network security Peers Peer-topeer network Print servers Server Switch Thin Clients WAN WLAN Fat clients LAN