networks

• state the two types of network

  - local area network

  - wide area network
• what is meant by a wide area network?

  - the computers are geographically remote

  - communication media is owned by a third party
• what is meant by a local area network?

  - the devices connected are in close geographical proximity

  - the communication media is owned by the company using it
• describe the difference between a lan and a wan

  - lan is over a small geographical area; wan is over a large geographical area

  - lan has its own dedicated infrastructure; wan uses external/shared infrastructure
• give 3 examples of where lans are used

  - small businesses

  - schools

  - universities
• give 2 examples of where wans are used

  - the internet

  - businesses with offices in multiple different countries
• list 3 examples of connection media that wans can use

  - telephone lines

  - satellite links

  - radio links
• what are the factors that affect network performance?

  - wifi frequency

  - interference

  - number of devices

  - type of network traffic

  - distance between devices

  - bandwidth

  - transmission medium

  - network latency

  - number of transmission errors
• how can wifi frequency contribute to network performance?

  - the higher the frequency, the more data can be carried per second
• how can interference contribute to network performance?

  - the objects may block the signal
• how can the number of users contribute to network performance?

  - each user has access to less bandwidth so there would be more collisions
• how can the type of network traffic contribute to network performance?

  - larger files like videos will take up more bandwidth than text files for example
• what is meant by bandwidth?

  - a measure of the amount of data that can transfer through a communications channel over a given period of time
• what is meant by latency?

  - a period of time delay in a computer system
• when does a collision occur?

  - when two devices on a network try to communicate simultaneously along the same communication channel
• what happens in a client-server model?

  - computers on the network each take the role of either the central server or a client
• what is the role of the client in a client-server network?

  - the client requests services from the server
• what is the role of the server in a client-server network?

  - the server processes the client's request and send a response back
• what services does a server provide?

  - storing files

  - printing

  - hosting a website
• why is a client-server network referred to as a centralised network?

  - the clients communicate with a central server
• what are the pros of a client-server network?

  - easier to keep track of files as they're stored centrally

  - easier to perform backups as they can be done centrally

  - easier to install and update software

  - easier to manage network security

  - servers are very reliable and are always on
• what are the cons of client-server networks?

  - expensive to set up and needs it specialists to maintain network and server

  - server dependence - if the server goes down then all clients lose access to their work

  - the server can become overloaded if too many clients are accessing it at once
• what is the structure of a peer-to-peer network?


  - each computer is directly connected together; they are all equal

  - this removes the need for a central server
• what are p2p network commonly used for?

  - file transfer

  - streaming video from computer to mobile or tv

  - wireless printing

  - bluetooth speakers
• what are the pros of a peer-to-peer network?

  - easy to maintain; no expertise or expensive hardware required

  - no dependence on server
• what are the cons of a p2p network?

  - no centralised management; devices need their updates and security installed individually

  - backups cannot be done centrally and so are more complicated

  - copying files between devices creates duplicate files; easy to lose track of what is stored where and which files are up-to-date

  - peer machines are less reliable and data may be lost if one fails

  - machines are prone to slow down when other devices access them
• list the hardware required to connect stand-alone computers into a lan

  - wireless access points

  - routers

  - switches

  - network interface card

  - transmission media
• what does a nic do?

  - internal piece of hardware which allows a device to connect to a network
• what does a switch do?

  - connects devices on a lan

  - they receive data and transmit this data to the relevant device on the network using its mac address
• what does a router do?

  - transmits data between networks

  - directing data packets to their destination on the internet
• where are routers often used?

  - homes and offices to connect the lan to the internet
• what does a wap do?

  - a wireless access point connects devices in a local area network using wifi
• list 3 common wired connection medias

  - ethernet

  - fibre optic cables

  - coaxial cables
• what is the structure of a common ethernet cable?

  - contains four pairs of copper wires; twisted together to reduce internal interference
• what is the structure of coaxial cables?


  - single copper wire surrounded by plastic layer for insulation and metallic mesh which provides shielding from outside interference
• how do fibre optic cables transmit data?

  - they transmit data as light
• what are some features of fibre optic cables?

  - high performance

  - expensive

  - do not suffer with interference

  - can transmit over very large distances without loss of signal quality
• what is the internet?

  - a worldwide collection of networks
• what is a dns?

  - domain name server

  - translates a website's domain name into its ip address
• how does a dns work?

  - the user sends a request to the nearest dns asking for the ip address associated with the desired domain name

  - the dns responds with the correct ip address

  - the client can then use this ip address to send their original request