QOS Recommendations for VoIP

QoS (quality of service) is a pre-defined and quantitatively determined level of service quality that is thought to be obtained from every communications network. In this regard, a VoIP (Voice over Internet Protocol) network has its own set of generalized specifications outlining its QoS; associated mainly the regulated transmission and reception of data (voice, video, and text) packets.

The term latency in VoIP refers to the delay caused during the processing and traveling of data packet from one network node to another. According to the recommendations made by ITU (international telecommunications union), the maximum latency period for a VoIP data packet must not exceed 150 milliseconds. In a VoIP network, the term jitter refers to the variations observed in the latency period of data packet delivery. This limitation is often perceived as unavoidable in nature. Formal recommendations suggest that this variation should not be over 0.5 milliseconds in a corporate VoIP network. The difference between latency periods of two communication sessions in VoIP should not be more than 0.5 milliseconds. Packet loss (or loss of data due to network traffic congestion/load) is a usual occurrence in global communication scenario. However, in a VoIP network, even single percent loss of data packets is practically not tolerated because these packets mainly contain encoded human speech signals. For this reason, network architects are recommended to design a VoIP network which has a maximum of 0.3 percent packet loss in its overall communication sessions.