Abstract:

Two forms of flow control for ATM (Asynchronous Transfer Mode) networks are examined, namely rate-based and credit-based flow control of ABR (Available Bit Rate) traffic. Under certain assumptions, these two are shown to be duals of each other. That is, the average traffic flow of a rate-based network can be achieved by controlling buffer space of a credit-based network. Similarly, the buffer requirements of a credit- based network can be achieved by controlling the rates in a rate-based network. Using the duality, it can be shown that several claimed advantages - in which some feature or attribute is claimed to be available in one form of flow control but not the other - are not advantages at all and, in fact, have corresponding implementations in the other. However, the duality is not perfect, and some asymmetries remain between these two forms of flow control. Some observations are offered to reduce the differences between these in practical networks.