quality of service (QoS)
refers to resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. For example, a required bit rate, delay, jitter, packet dropping probability and/or bit error rate may be guaranteed. Quality of service guarantees are important if the network capacity is insufficient, especially for real-time streaming multimedia applications such as voice over IP, online games and IP-TV, since these often require fixed bit rate and are delay sensitive, and in networks where the capacity is a limited resource, for example in cellular data communication. In the absence of network congestion, QoS mechanisms are not required.
A network or protocol that supports QoS 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.
Applications requiring QoS
1. streaming multimedia may require guaranteed throughput to ensure that a minimum level of quality is maintained.
2. IPTV offered as a service from a service provider such as AT&T's U-verse
3. IP telephony or Voice over IP (VOIP) may require strict limits on jitter and delay
4. Video Teleconferencing (VTC) requires low jitter and latency
5. Alarm signalling (e.g., Burglar alarm)
6. dedicated link emulation requires both guaranteed throughput and imposes limits on maximum delay and jitter
refers to resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. For example, a required bit rate, delay, jitter, packet dropping probability and/or bit error rate may be guaranteed. Quality of service guarantees are important if the network capacity is insufficient, especially for real-time streaming multimedia applications such as voice over IP, online games and IP-TV, since these often require fixed bit rate and are delay sensitive, and in networks where the capacity is a limited resource, for example in cellular data communication. In the absence of network congestion, QoS mechanisms are not required.
A network or protocol that supports QoS 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.
Applications requiring QoS
1. streaming multimedia may require guaranteed throughput to ensure that a minimum level of quality is maintained.
2. IPTV offered as a service from a service provider such as AT&T's U-verse
3. IP telephony or Voice over IP (VOIP) may require strict limits on jitter and delay
4. Video Teleconferencing (VTC) requires low jitter and latency
5. Alarm signalling (e.g., Burglar alarm)
6. dedicated link emulation requires both guaranteed throughput and imposes limits on maximum delay and jitter
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