Performance of an in-call buffer-window reservation/allocation scheme for long file transfers

The authors evaluate the performance of both the fixed buffer allocation (FBA) and the adaptive buffer allocation (ABA) schemes, in which the network nodes are allowed to offer less than the requested buffer size. The performance measures of interest are the blocking probability, file transfer delay, and the adaptation speed for ABA for a given buffer size and the offered load. The authors develop and analyze a quasi-birth-death model of the ABA scheme (with exponential file lengths and negligible delay in carrying out reservation and cancellation procedures). In particular, they develop a recursive computational scheme exploiting the structure of the underlying model. This is supplemented by a first-passage time analysis to evaluate the transient behavior of the control strategy. The authors use both analytic and simulation methods. The results demonstrate that the ABA schemes provide significant advantages over the FBA scheme if the parameters are appropriately chosen. They also provide guidelines on the choice of these parameters