A group of interconnected computers/devices connected for the purpose of communication
Network
Connected by wired medium like cables or wireless medium like Wi-Fi
A computer/device not connected to a network is called a stand-alone device
Many different types of computer are connected to some form of network today, including PCs, smartphones, smartwatches, etc.
Advantages of using networks
File sharing
Hardware sharing
Communication via email, chat, video
Roaming access
Additional benefits of larger networks used by businesses and schools
Centralised maintenance and updates
Centralised security with anti-virus and firewalls
User monitoring
Levels of access
Disadvantages of networks
Cost of additional equipment
Management by technical staff
Spread of malware
Hacking risks
Once a device is connected to a network, it is possible that data may be accessed without the device owner's permission
Local area network (LAN)
A network of computers that covers a small area, eg a school or college
Wide area network (WAN)
A network that spans across a building, buildings or even countries, eg the internet
A LAN is geographically confined to one building or site
A WAN is spread over a wide geographical area
Examples of LANs
Networks employed by small businesses, small organisations, schools, colleges, universities and in homes
LANs are owned and maintained by the organisation
Organisations that have more than one office or branch, such as banks, tend to use a WAN
The WAN allows the head office to communicate and share data with the sub-offices and branches
Communication in a WAN is done through national telephone infrastructures or via wireless transmission
Each office or branch in a WAN has its own LAN that is connected together using the WAN
The internet is essentially a huge, international WAN
Network
A group of interconnected computers/devices
Network performance
Response time - how fast a message can be sent or how quickly a document can be retrieved
Factors that affect network performance
Number of devices on the network
Bandwidth of the transmission medium
Type of network
Network traffic
Network latency
Number of transmissions
Transmission errors
Bandwidth
Measures the amount of data that can transfer through a communications channel over a given period of time
Typical bandwidth of transmission media
Twisted copper wire: Up to 10 gigabits (Gb) per second
Fibre-optic cable: Up to 100 gigabits (Gb) per second
Wi-Fi (home networks): Up to 600 megabits (Mb) per second
Business Wi-Fi: Up to 6 gigabits per second
Bandwidth sharing
Bandwidth of the medium is shared between each connected device
If ten devices were connected, the bandwidth allocated to each device would drop to 5.4 Mb per second, thereby reducing the rate at which data can be sent to any particular device
Latency
A measure of how long it takes a message to travel from one device to another across a network
Latency
Low latency experiences few delays in transmission
High latency experiences many delays
Hub-based network
Usually experiences higher latency than a switch-based network because hubs broadcast all messages to all devices
The greater the number of devices connected to a network, the more important the choice of transmission medium becomes
Many networks include a combination of fibre-optic cables, twisted copper wire, and Wi-Fi
Collision
The result of two devices on a network trying to communicate with each other simultaneously
The greater the number of devices on a network, the more chance of a collision occurring, and the longer it takes to transmit a message
Local area network (LAN)
A group of interconnected computers/devices
Hardware
The physical parts of a computer system, eg a graphics card, hard disk drive or CD drive
Network interface controller (NIC)
A circuit board that is installed in a computer so it can be connected to a network
Wireless
A connection that does not need wires and transmits data through radio signals
Transmission medium
Physical devices that are used to transfer data
Router
A device for connecting computers and other network capable devices together to form a network
Hub
A piece of hardware used in computer networks used to connect multiple devices
Switch
A device for connecting computers and other network capable devices together to form a network