What Is QoS?

Date First Published: 9th April 2022

Topic: Computer Networking

Subtopic: Network Services

Article Type: Computer Terms & Definitions

Difficulty Level: 7/10

Learn more about what QoS is in this article.

Short for quality of service, QoS is the prioritisation of network traffic, such as video and audio and it only applies to network traffic generated for time-sensitive communication, such as VoIP, streaming media, and video calls. QoS is vital for the transport of traffic as it guarantees a certain level of performance to a data flow.

Note:

QoS also refers to a measure of the overall performance of a service, such as telephony, a computer network or a cloud computing service. The aspects of the network considered are latency, jitter, error rate, uptime, bandwidth, bit rate, availability, and data packet loss.

Definitions

In 1994, QoS was defined by the ITU. QoS has slightly different definitions in the field of telephony and networking.

In telephony, it consists of all the requirements of all the aspects of the connection, such as the service response time and loss, signal-to-noise ratio, crosstalk, interrupts, frequency, loudness levels and more. It refers to the achieved quality of service.

In networking, QoS refers to traffic prioritisation and resource reservation rather than the achieved quality of service. For example, a network administrator might set a higher priority on internal network traffic rather than external traffic. QoS is responsible for prioritising sent data packets, which is what sent data is broken down into. The purpose of this is to get the most out of the limited amount of bandwidth in a network as networks can only send a certain amount of data within a certain period of time.

The prioritisation of packets ensures that bandwidth is used to provide better internet service in that fixed span of time. An example of this is prioritising data packets related to a video call rather than an email download. This is because video calling is a time-sensitive form of communication than email and it needs to happen in real-time. The dropping of data packets during a video call will cause latency and jitter in the call. However, if the data packets were dropped or delayed in the email process, it is still possible for them to be sent afterwards and the user will not experience any failure of service.

QoS tools take a look at packet headers, which contain information about what the packet contains and where it is going, to prioritise packets. In addition, QoS tools can take a look at the packet header and determine whether a packet is related to time-sensitive communication, such as video streaming or video calling and prioritise it.

Importance

QoS is very important, especially in businesses. Without QoS, the data of a network can become disorganised and it could cause networks to become clogged, causing the performance to drop. In addition, it is more likely that data integrity and security would be compromised in a business with poor QoS. A lot of employees and customers rely on communication services to complete their jobs.