Performance analysis of the dual cell spacer in ATM systems

In this paper, we d e v elop an analysis of the so-called Dual Spacer. In contrast to a conventional spacer, which shapes a traac stream only according to a given Peak Cell Rate, the Dual Spacer takes into account the Peak Cell Rate as well as the Sustainable Cell Rate with the corresponding Burst Tolerance. By shaping, also according to a Sustainable Cell Rate, the Usage Parameter Control function can monitor a bursty cell stream more eeciently. The analysis is carried out in discrete-time domain and performance measures like the cell rejection probability, the cell delay distribution and the inter-departure time distribution are derived. All results are of exact nature. Numerical examples which compare the performance of the Dual Spacer with that of a conventional one show a similar performance in terms of delay and cell loss for relatively small values of the Burst Tolerance. Using our analysis, the couple Sustainable Cell Rate/Burst Tolerance, which is used for traac shaping in case of the Dual Spacer, can be chosen adequately to achieve a given target cell rejection probability or a mean delay, respectively, and to allow t h e network provider to obtain a maximal multiplexing gain.