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[+44 330 383 8000](tel:+443303838000 "+44 330 383 8000") ![](/images/getstarted-writetous-navbar-int_ZY7MOf.webp) ### Write to us Fill out our request form. Our experts will respond as soon as possible. [Write to us](/gb/request-information "Write to us") ### Quality of Service (QoS) [Quality of Service in IP networks](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/qos#section-3) [QoS requirements in Voice-over-IP telephony](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/qos#section-4) # Quality of Service (QoS) The acronym QoS stands for the technical term "Quality of Service". QoS defines specific quality requirements which must be met to use a communication service with the desired quality from the subscriber’s perspective. In order to meet these requirements, different actions, parameters and processes are defined depending on the network used or the transfer method, summarised under the term QoS. One can essentially distinguish between the transmission quality and the traffic quality. Whilst the traffic quality primarily pertains to the transmission technology and establishing the connection, the transmission quality pertains to the actual information transfer over a network. ### Quality of Service in IP networks Unlike conventional circuit-switched telephone networks, IP networks are packet-oriented. In order to use these networks to transmit time-sensitive services, there are special requirements with respect to Quality of Service. The key parameters describing the service quality of an IP network are latency, jitter and the packet loss rate. Latency refers to the a packet’s delay which occurs end-to-end during transmission. Jitter measures how much latency deviates from a mean. Lastly, the packet loss rate specifies the percentage of IP packets lost during transmission. ### QoS requirements in Voice-over-IP telephony [Voice-over-IP telephony (VoIP telephony)](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/voice-over-ip) is a time-sensitive service with specific QoS requirements for the transmitting network. Voice can only be transmitted in a high quality if these requirements are met. To operate telephone systems via IP network or use the services of a [cloud telephone system](/gb/en/products/cloudya), it is necessary to first verify whether the network is able to provide the required quality of service. Transmission delay and the packet loss rate are particularly key in assessing voice quality. Whilst the loss of individual packets or delays under 100 milliseconds are hardly noticeable by the human ear, high loss rates or delays can result in high communication interference. To ensure the networks are able to meet the QoS requirements, they feature mechanisms to give priority to certain IP packets (voice packets) and delay others. ### Related Articles ### Voice over Internet Protocol (VoIP) **What is VoIP?** The **Voice over Internet Protocol,** also called IP telephony, is a method of communication for making calls over a broadband Internet connection as an alternative to regular calls made over an analogue phone using the [PSTN](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/pstn). These VoIP calls can happen entirely over the Internet but where required, gateways also link to the PSTN. This means that VoIP users can still connect to anyone with a telephone number including local, mobile, and international numbers. VoIP services can be accessed from a computer with a so-called [softphone,](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/softphones) from an IP phone, from a smartphone or from a conventional landline phone that is connected to a VoIP adapter. 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