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This paper discusses quality deterioration in Asynchronous Transfer Mode (ATM) networks and suggests a design procedure for providing better service quality provision for voice, data and video communications. Delay due to cell assembly/processing and cell loss due to bit error are estimated by analyzing stochastic cell defects. The optimum delay and cell loss rate satisfying customer needs proves to be restricted within a region. 13.6.1.

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In order to evaluate connection quality, the lost call situation in a network is measured and analyzed, and then the management of actions for improvement is considered. However, even if the lost call situation is measured and analyzed, the cause of call loss is only partially identified since the routing data cannot be acquired for each call in current communication networks. Thus, the results cannot be reflected in actions for quality improvement. This article proposes a method to discriminate which of the two major kinds of call loss has occurred in a communication network. The possibility of discrimination of call loss causes is examined by generating a pseudo call loss for the case where the probabilistic call distribution is included in the network and also for the case where it is not. Probabilistic call distribution not related to the priority or nonpriority, regardless of the derouting scheme, in which a new link is sought when all circuits in the priority link are busy, can occur. It is shown that the usefulness of the proposed method is limited when call distribution occurs and there exist many links. On the other hand, when call distribution does not occur, discrimination is possible in more than 75% of cases when the blocking probability is 1% or above. In other words, it is shown that the discrimination method proposed in this article has sufficient discrimination accuracy from the practical viewpoint. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(2): 74–83, 2000