Performability of an Algorithm for Connection Admission Control

Connection admission control (CAC) in broadband, ATM-based telecommunication networks is a problem of recognized importance. Its solution calls for real-time algorithms that can accurately decide whether a connection request may be granted without compromising specified quality of service (QoS) requirements. We consider an algorithm for this purpose that accommodates variable bit rate (VBR) connections and is based on effective bandwidth computations. Arriving VBR traffic streams are assumed to be leaky-bucket regulated and are represented by worst-case, periodic, on-off, fluid sources that are randomly phased. Moreover, certain traffic classes may benefit from statistical multiplexing (S-VBR), while others may not (NS-VBR). We then evaluate the ability of such a CAC algorithm to perform in the presence of fluctuating channel capacity, where the performability variable Y/sub T/ is the fraction of some specified busy period T during which the quality of service requirement is violated. A general base model that supports Y/sub T/ is then formulated and instances of the resulting performability model are constructed and solved using UltraSAN. In particular, the evaluation experiments reveal some interesting differences in how QoS degrades with respect to the control of S-VBR vs. NS-VBR traffic.