Factors of Network Performance (OCR GCSE Computer Science)
Revision Note
Written by: James Woodhouse
Reviewed by: Lucy Kirkham
Factors of Network Performance
What are the factors that affect network performance?
5 key factors can impact how well a network performs
Number of Users
Bandwidth
Latency
Error Rate
Transmission Media
Number of users
This is how many users are on the network at the same time
Too many users can cause the network to slow down if there is not enough bandwidth for all of the data being sent and received
Bandwidth
Bandwidth is the amount of data that can be sent and received at any given time
Measured in bits per second (bit rate)
A smaller bandwidth means that less data can be sent and the network can slow down, potentially to the point of becoming unusable
Latency
Latency is the delay between data being sent and received
If there is a big delay between the two, more data will be on the network causing collisions
This can lead to even more packets of data being sent as the error rate has increased
Error rate
Error rate is the measure of how many packets of data do not reach their destination
An increased error rate occurs in less reliable connections - a poor wireless signal would be a contributing factor to an increased error rate
Transmission media
Transmission media is the type of cable used in wired connections
Wired connections offer a higher bandwidth than wireless connections
The main options for transmission media are unshielded twisted pair and fibre-optic
Fibre optic has a higher bandwidth than copper cabling as well as faster transfer speeds
Worked Example
A university has a LAN (Local Area Network). The LAN allows access by both wired and wireless devices. Users have reported that the network sometimes runs very slowly.
(i) Explain why the number of devices using the network at the same time can affect the performance of the network [3]
(ii) Identify one other factor that can affect the performance of the network [1]
How to answer this question
To answer this question there must be an answer with an explanation of its impact
An example answer that would score full marks
More devices accessing the network at one time would result in the network performing slower because the bandwidth would be split between them [1]
The impact of this would mean that there is less bandwidth for each device, slowing down how fast data could be sent and received [1]
Having more users/devices means that there is more data being sent and received [1]
Answers
(i)1 mark each to a maximum of 3
Slower transmission of data // less data can be transmitted at the same time // the transmission rate decreases // time to send/receive increases
More devices mean more data is being transmitted at a time
Bandwidth will be split between all the devices sending data // each device uses some of the bandwidth
this means that there is less bandwidth for each device
Devices have to wait longer before they can transmit // increased latency
If the maximum bandwidth is used then devices cannot transmit
Central device/switch/router has to handle more requests and may run slower
More collisions are likely) // higher error rate
This means more data has to be retransmitted
Loss of more packets
This means more data has to be retransmitted
(ii) 1 mark
Bandwidth
Interference // with example
Wired // wireless // transmission medium
Type/amount of data being transmitted
Central hardware performance // with example
e.g. router/switch
Error rate
Distance between nodes
Topology // physical layout
Wireless repeaters
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