Analysis of the Leaky Bucket Algorithm for ON-OFF Data Sources

Abstract

The leaky bucket algorithm has been proposed as an important element in the rate-based management of bandwidth in high-performance, integrated packet communication networks. In this paper, the leaky bucket algorithm is analyzed for ON-OFF data sources, which may be characterized by their average data rate, peak data rate, and average number of bits generated during an ON period. A fictitious queue is used to model the behavior of the leaky bucket algorithm, and a two-state Markov-modulated rate process is used to model the ON-OFF data source. The analysis applies to buffered and unbuffered leaky buckets with rejecting or marking of violating data. Simple, closed-form expressions are derived that relate the leaky bucket parameters (bucket size and rate) and the ON-OFF source characteristics to the loss and mark probabilities and the leaky bucket queueing delay. The required bucket size is shown to increase linearly with the average number of bits generated during an ON period, and increase logarithmically with the decrease in loss or mark probability. For a buffered leaky bucket, we also show that the bucket size increases logarithmically with the decrease in the average delay in the leaky bucket queue.