Defining Quantiles for Estimating IP Packet Delay Variation in NGN Core Networks

Abstract

Traffic delay is one of the important metrics used for evaluating network performance. Delay and delay variationcharacteristics of IP packets transferred over multi-section networks can be derived, estimated or composed from componentdistributions of IP package delay in each network section. Approximate methods are needed in the cases of unknown orcomplicated delay distribution functions, which are unavailable or unusable in practice. The ITU-T has proposed a methodfor estimating IP packet delay variation. One of noticeable factors affecting the estimation accuracy is the packet delaypopulation quantile which has not been adequately considered. The objective of this paper is to examine the optimalrange of quantiles used for estimating the IP packet delay variation in the NGN (Next Generation Network) core networks.The paper is composed from the following ideas. Firstly, several concepts and mathematical formulas related to delaymetrics based on probability and statistics theory are defined. The approximate method of ITU-T for estimating the IPpacket delay variation in a multi-section network is revised. Then, another method based on convolution for composingthe empirical IPTD distribution functions is proposed for the same target as the first one. Secondly, a number of test casesare implemented to measure the IP packet delay on several sections of an NGN core network. Sample data are used forcomputing and estimating the IP packet delay variation for multi-section networks by two methods with certain hypotheses.Finally, these methods are compared and evaluated both theoretically and empirically in regards to the estimation accuracyversus quantiles of the IP packet transfer delay. The best range of quantiles is determined to ensure the accuracy of theestimation method applied for the NGN core network.