Performance analysis of a rate-control throttle where tokens and jobs queue

A rate-control throttle is used for overload control in distributed switching systems and computer and communication networks. Typical implementations of the throttle have a token bank where an arriving job is blocked and rejected if the bank is empty of tokens. The author examines an expanded implementation where an arriving job queues in a finite buffer when the token bank is empty. It is shown that the steady-state throughput and blocking of jobs depends on the capacity of the job buffer and the capacity of the token bank only via the sum of the two capacities, not on their individual values. Thus, the job buffer per se is not needed to enhance the robustness of the throughput of the throttle to unknown exogenous job arrival rates. However, a job buffer (along with a token bank) with adjustable buffer capacities does have the potential to shape the departure process and to adapt between a delay control and a work-rejection control