CELL VERSUS MESSAGE LEVEL PERFORMANCES IN ATM NETWORKS

The goal of this paper is to provide some insight into the relations t hat exist between cell level and message level performance guarantees in the context of ATM networks. Cell level guarantees are typically wh at the network is capable of providing, while message level guarantees are the ones of interest to users. It is, therefore, important to und erstand how the two are related, and which factors influence this rela tion. There are many different performance measures that are of import ance, and in this paper we try to touch on the (three) most relevant o nes. This includes comparing cell and message loss probabilities, aver age cell and message delays, and cell and message jitter. Specifically , we show that cell and message loss probabilities can exhibit signifi cant differences, which strongly depend on traffic characteristics suc h as peak rate and burst size, i.e., for a fixed cell loss probability , the message loss probability can greatly vary when peak rate and bur st size change. One reason for this sensitivity, is that message loss depends on what happen to all the cells in a message. For delay and ji tter, we also find that peak rate and burst size play a role in determ ining the relation between cell and message performance. However, this sensitivity is not as acute as with losses since message delay and ji tter are typically determined by the performance seen by only one cell , the last cell in a message. In the paper, we provide quantitative ex amples that illustrate the range of behaviors and identify the impact of different parameters.