By the end of this lesson, you will be able to:
- Identify things that affect how well a network performs
- Explain how they impact performance
- Suggest ways to improve network performance
Factors
Network performance is about response time - how fast a message can be sent or how quickly a document can be retrieved. The performance of a network can be affected by various factors:
- the number of devices on the network
- the bandwidth of the transmission medium
- the type of network traffic
- network latency
- the number of transmission errors
- Any network can be affected by one or a combination of these factors.
Bandwidth is a measure of the amount of data that the medium can transfer over a given period of time. Each transmission medium has a different bandwidth:
| Medium | Typical brandwith |
|---|---|
| Twisted copper wire | Up to 1 gigabit (Gb) per second |
| Fibre-optic cable | Over 40 terabits (Tb) per second |
| Wi-Fi | About 54 megabits (Mb) per second |
| Business Wi-Fi | Up to 1 gigabit per second |
Each connected device requires bandwidth to be able to communicate. The bandwidth of the medium is shared between each connected device. For example, a home Wi-Fi network with one device would allocate 54 Mb per second to that device. If a second device joins the network, the bandwidth would be split between the two, giving 27 Mb per second to each, and so on. 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.
In reality, however, things are more complicated. Different types of network traffic usually have different bandwidth requirements. For example, streaming a high definition video requires more bandwidth than streaming a low definition video. Some network switches are capable of determining the type of traffic and adjusting the bandwidth allocated to a particular device to accommodate the traffic’s requirements.
Latency
Network latency is a measure of how long it takes a message to travel from one device to another across a network. A network with low latency experiences few delays in transmission, whereas a high latency network experiences many delays. The more delays there are, the longer it takes to transmit data across a network.
Latency is affected by the number of devices on the network and the type of connection device.
A hub-based network will usually experience higher latency than a switch-based network because hubs broadcast all messages to all devices. Switch-based networks transmit messages only to the intended recipient.
The greater the number of devices connected to a network, the more important the choice of transmission medium becomes. Wi-Fi generally handles less traffic than twisted copper wire (TCW), which in turn handles less traffic than fibre-optic cable. Many networks include a combination of all three media:
- fibre-optic cables allow high data transmission between different buildings
- TCW runs from switches within buildings to individual devices
- Wi-Fi allows guest devices to connect to the network
Transmission errors
Inevitably there will be times when devices try to communicate with each other at the same time. Their signals collide with each other and the transmission fails. It is similar to when two people speak to each other simultaneously - neither person is able to clearly hear what the other person is saying.
A collision occurs when two devices on a network try to communicate simultaneously along the same communication channel. 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.