Quality of Service (QoS)

Qualityof service

Quality of service (QoS) is the overallperformance of a telephony or computer network, particularly the performanceseen by the users of the network.

To quantitatively measure quality ofservice, several related aspects of the network service are often considered,such as error rates, bit rate,throughput, transmission delay, availability, jitter, etc.

Quality of service is particularlyimportant for the transport of traffic with special requirements. Inparticular, developers have introduced technology to allow computer networks tobecome as useful as telephone networks for audio conversations, as well as supportingnew applications with even stricter service demands.

Definitions

In the field of telephony, quality ofservice was defined by the ITU in 1994. Quality of service comprisesrequirements on all the aspects of a connection, such as service response time,loss, signal-to-noise ratio, crosstalk, echo, interrupts, frequency response,loudness levels, and so on. A subset of telephony QoS is grade of service (GoS)requirements, which comprises aspects of a connection relating to capacity andcoverage of a network, for example guaranteed maximum blocking probability andoutage probability.