Performability of an Algorithm for Connection Admission Control

J. F. Meyer


Connection admission control (CAC) in broadband, ATM-based telecommunication networks is a problem of recognized importance. 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 YT  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 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.

Keywords: Broadband telecommunication networks, connection admission control (CAC), effective bandwidth, performability, variable bit rate (VBR) traffic.

Compressed PDF File: