POLICING AND TRAFFIC SHAPING AT THE USER-NETWORK-INTERFACE (UNI)

A network's decision to accommodate a new ATM connection is based in p art on sustained and peak cell rate and peak duration declared by the user in the connection request. As these traffic descriptors are only projections of the traffic, connection admission control must be suppl emented by input rate control in order to monitor and regulate the act ual traffic. None of the proposed input rate control schemes enforces multiple traffic parameters. Additionally, traffic shaping at the UNI based on regulating average and peak rates may enhance statistical mul tiplexing performance. This paper presents a performance analysis of t he two-stage entry monitor combining a sticky buffer policer with a sp acer. To the best of our knowledge, no analysis of tandem policers has appeared before this paper. The first stage enforces the sustained ra te R/T negotiated in the connection request; the spacer shapes the tra ffic and controls burstiness by further ensuring that cells enter the network at least S slots apart. We derive the probability generating f unction for the combined queue length distribution and evaluate numeri cally (i) the manner in which S and burstiness affect the cell loss pr obability, and (ii) the performance penalty caused by enforcing two ra tes. The principal contribution of this paper is the calculation of th e buffer size required to police two parameters subject to a specified cell-loss ratio. Our principal conclusion is that the increase in buf fer size needed to police the peak sustained rate in addition to the s ustained rate is minimal. We will also demonstrate that the leaky buck et and the single-stage sticky buffer have comparable performance, ena bling us to conclude that a two-stage sticky buffer can police both pe ak and sustained rates for almost the same cost as a leaky bucket.