Networks Flashcards
What is a network?
An arrangement of two or more computing devices (nodes) connected together in order to communicate with each other and share resources
Give some reasons for connecting computers in a network.
- To share data and software / share hardware peripherals (printers, hard drives, etc.) / share internet connections and services
- To support collaborative working / provide centralised support and backup services
- To enable rapid employment of new software and updates / enable people to communicate with each other using services (e.g. email)
Give 3 different types of networks.
- PAN - personal area network
- LAN - local area network
- WAN - wide area network
Describe what is meant by a PAN.
A network within the range of an individual person
Describe what is meant by a LAN.
- A network in a small area (e.g. a home, school, office building) or group of buildings on a site, existing within a small geographical area
- Usually managed by local manager or team at site
Describe what is meant by a WAN.
- A network that connects separate LANs over a large geographical area
- Large companies connect LANs at different sites to share data and resources
- Managed by several different people or parts of an organisation working together / each LAN could be managed independently
Give 2 network usage models.
- Client-server
- Peer-to-peer
Describe what is meant by a client-server network.
- A network containing a server that can back up and store data centrally
- All other devices each considered a ‘client’, may be more than one server
Describe what is meant by a peer-to-peer network.
- A network configuration containing no central server
- Each device equal in responsibility, each with the ability to work as a client and a server
Name the two network structures that describe the way in which data within the network is transmitted.
- Wired (e.g. via cables)
- Wireless
State what is meant by ‘range’ in terms of data transmission.
The distance over which data can be transferred
State what is meant by ‘bandwidth’ in terms of data transmission.
The capacity at which a network can transmit data
State what is meant by ‘latency’ in terms of data transmission.
The delay in time between data being transferred and the instruction which caused the transfer
Two types of cables most commonly used for networks are copper wire and fibre-optic cables.
Give some characteristics of copper wire cabling.
- Made of thin copper strands, transmits data as electrical signals
- High noise contamination
- Prone to external interference
- Low bandwidth
- Easy installation / fairly cheap installation
Two types of cables most commonly used for networks are copper wire and fibre-optic cables.
Give some characteristics of fibre-optic cabling.
- Very low noise contamination
- Not affected by magnetic interference - data carried using beams of light
- Secure/reliable data transmission
- Much higher bandwidth over a longer distance
- Difficult installation/maintenance
- Expensive due to cost of electrical components - although does not corrode
- Made of glass so more fragile
Give some forms of wireless transmission media.
- Wi-Fi
- Bluetooth
- Zigbee
- RFID
- NFC
Describe the aspects of using wired transmission media to create a LAN.
- Difficult installation - Each device needs own dedicated cable
- Limited flexibility - Number and location of cable connections is fixed, making changes once set up is likely to disrupt LAN
- Long range
- High bandwidth
- Low latency - Cables have protective coverings, less susceptible to interference
- Good security - Impossible to tap into physical cables without being in same location as cable
Describe the aspects of using wireless transmission media to create a LAN.
- Easy installation - Adding new devices easy, only WAPs to be connected by cable
- Versatile - Devices can be moved around without losing connection, new users added easily
- Short range - Walls and other physical obstacles may obstruct signal
- Low bandwidth - All active devices must share available bandwidth
- High latency - Susceptible to interference from other wireless networks or devices
- Poor security - Anyone within range can intercept transmissions
What is meant by ‘network speed’?
The rate at which data is transferred within a network
What are network speeds measured in?
Bits per second, bps
(e.g. Mbps, Gbps)
What is the equation to calculate the rate at which data is transferred?
Data transfer rate (bps) = File size (bits) ÷ Time (s)
Data transfer rate is measured in base-10 units.
Recall the values corresponding to each of the correct units.
What is a network topology?
The way in which devices on a network are physically arranged and connected together
Give four examples of network topologies.
- Bus
- Star
- Ring
- Mesh
Give some characteristics of a bus topology.
- Each device connected to main communication line called ‘bus’
- Single cable functions as backbone of network, acting as shared communications medium that all devices connect to via an interface connector
- When a node communicates, data is transmitted down bus which all devices receive, but only intended recipient accepts and processes message
Give some advantages of using a bus topology.
- Easy and cheap to install/set up compared to other wired networks because it only requires a small quantity of cables
- Easy to add new devices
Give some disadvantages of using a bus topology.
- High risk of data collisions occurring when multiple devices transmit data at the same time - devices detect collisions and resend data, slowing down network speed
- If main cable fails or is damaged, whole network will fail
- Whole network will fail if a terminator is removed as they ensure data is not caught at ends of bus, ensuring data sent in the correct direction on network
Give some characteristics of a star topology.
- All nodes on network connected to a hub
- Central connection point of a ‘hub node’, could be a device such as a network hub, switch or router
- (Router on its own cannot be the hub node - needs to be linked to a switch)
Give some advantages of using a star topology.
- Data is only sent to the intended computer directly
- The transmission medium is not shared so there can be multiple simultaneous communications
- Failure of one node or link doesn’t affect rest of network, it is easy to detect a failure and troubleshoot it as it allows isolation of each device within network
- It is easy to add new devices without disrupting the network
Give some disadvantages of using a star topology.
- If the central point fails, then so will the entire network
- Increased overall cost of network - requires a lot of cabling because each node connects individually to a central component
- Performance and number of nodes which can be added depends on capacity of the central device
(Exam-style question)
Describe how a star topology is implemented on a wireless LAN. (1)
The wireless router acts as a central hub, with individual devices communicating directly with it
Give some characteristics of a ring topology.
- Each device has two neighbouring devices
- Data is passed around in the same direction - either clockwise or anticlockwise
Give some advantages of using a ring topology.
Messages being sent between two workstations pass through all the intermediate devices, so a central server is not required
Give some disadvantages of using a ring topology.
- The failure of any cable within network can cause entire network to crash
- Maintenance or changes being made to the network nodes can impact the performance of whole network
Give some characteristics of a mesh topology.
- Each node connects to at least two other nodes and can connect to every other network node - this arrangement is referred to as being ‘fully connected’
- It is the most expensive type of network to install
Give some advantages of using a mesh topology.
- Mesh networks can heal themselves automatically when a break occurs, so there’s no interruption of service to any node
- Mesh networks get bigger and faster as more nodes are added
- Data can be transmitted from different devices simultaneously
- Can handle high volumes of data traffic as there is always an alternative route for data (e.g. for if one node fails)
Give some disadvantages of using a mesh topology.
- This type of network involves more cabling or more wireless devices, leading to higher cost
- Difficult to manage and requires expert supervision
- Mesh networks are still in development - a full set of recognised standards have not been adopted yet
What is the radio frequency used by smartphones to connect to Wi-Fi?
2.4GHz
What is 3G?
- It is the third generation of wireless mobile telecommunications technology
- Allows mobile phones and other devices to connect to internet wherever the device is located, by using a network of phone towers to pass signals
- Faster data transfer rates than previous generations, enabled mobile devices to access the Internet, and provided greater cybersecurity
What is 4G?
- 4G is the fourth generation of mobile phone technology for connecting to/communicating on a network
- Addresses previous issues of 3G such as the congestion of data on a network and speed - allowed people to use services that demand more capacity, also features reduced latency
- 4G-enabled devices communicate to the base station (mast) which then relays data from the internet to your device
What is 5G?
- The fifth generation of cellular networks - runs on same radio frequencies that are currently being used for smartphones
- Provides faster connectivity speeds, ultra-low latency and greater bandwidth
- Greater bandwidth improves quality of internet services in crowded areas
(Exam-style question)
Carlo’s smartphone can use 3G, 4G and 5G mobile communication standards.
Give one advantage of using a higher frequency band for mobile communications. (1)
Any one from:
- Higher frequency has more waves per second / carries more data in the same time
- Higher frequency gives greater bandwidth
- Higher frequency is more stable / less prone to interference
(Exam-style question)
Carlo’s smartphone can use 3G, 4G and 5G mobile communication standards.
Explain one benefit to Carlo of using 5G rather than 3G. (2)
Any one from:
- Gives Carlo faster responses to his communications/connections allowing Carlo to download/share data in a shorter time
- Gives Carlo more reliable communications/can access communications in more places giving Carlo a better user experience
- Gives Carlo more secure communications, improving his privacy/reducing other people’s ability to intercept/spy on his communications
