QoS (Quality of Service) - Definition
Quality of Service refers to resource reservation control mechanisms. Quality of Service can provide different priority to different users or data flows, or guarantee a certain level of performance to a data flow in accordance with requests from the application program or the internet service provider policy. Quality of Service guarantees are important if the network capacity is limited, for example in cellular data communication, especially for real-time streaming multimedia applications, for example voice over IP and IP-TV, since these often require fixed bit rate and may be delay sensitive.
A network or protocol that supports Quality of Service may agree on a traffic contract with the application software and reserve capacity in the network nodes, for example during a session establishment phase. During the session it may monitor the achieved level of performance, for example the data rate and delay, and dynamically control scheduling priorities in the network nodes. It may release the reserved capacity during a tear down phase.
The term Quality of Service is sometimes used as a quality measure, with many alternative definitions, rather than referring to the ability to reserve resources. Quality of Service sometimes refers to the level of Quality of Service, i.e. the guaranteed service quality. High QoS is often confused with a high level of performance or achieved service quality, for example high bit rate, low latency and low bit error probability.
QoS (Quality of Service) - Synonyms
Quality of Service; QoS; QoS VoIP; VoIP QoS