Queueing network models of credit-based flow control

Credit-based flow control schemes are a commonly used means of preventing buffer overflow in high-speed networks spanning a local area. Fibre Channel, a widely-used storage area networking technology, and InfiniBand, a recently developed system area network technology, are examples of two network technologies that employ credit-based flow control. With credit-based flow control, the receiver sends credits to the sender to indicate the availability of receive buffers; the sender waits for credits before transmitting messages to the receiver. We present two models of credit-based flow control operation. In particular, we consider a fork-join queueing system with two input queues; the message population feeds one queue and the credit population the other. We consider the case of bulk message arrivals and single arrivals drawn from a finite population. Our analysis yields stationary probability distributions for message queue length and number of available credits. We provide equations for mean message queue length, mean number of credits, throughput, and mean message waiting time.