Perform ability Evaluation of Telecommunication Networks

Digital telecommunication networks represent a fusion of concepts, techniques, and technologies from the fields of both communication and computing. The evaluation of such systems can likewise draw on methodologies which have evolved in both disciplines, bringing them together in a fashion that is suited to the needs of integrated services digital networks. With this aim, we discuss how quality of service (QOS) and its associated service performances are viewed by the telecommunications industry (per recent CCITI recommendations), and compare them with concepts of performance, dependability, and performability that have emerged within the computing community. We find that QOS and performability are compatible notions, where each reflects the combined influence of factors associated with both performance (in the strict sense) and dependability. Unlike the CCnT view of QOS, however, performability is conceptually a measure, thus providing an effective means of defining actual QOS measures. Model-based performability evaluation is then reviewed, with an emphasis on techniques which appear most applicable to to complex telecommunication networks.