Supporting Real-Time Applications

This second Clark, Shenker, and Zhang paper presents a queueing algorithm and architecture for differentiated services. The conceit is separating traffic into two classes, one with real-time requirements and one with more flexible latency requirements. To do so, they allow the network to make service commitments, essentially providing admission control and resource reservations. They also propose a new queuing discipline, FIFO+ to address sharing between flows.

This work seems incomplete, at best, to me. The authors mention off-hand that a pricing model will be essential to provide proper incentives for the system to work correctly, yet there is no discussion of how this would fit into the rest of the scheme. Even Shenker admits in his later paper that this work is particularly unmotivated; one does not get a sense that the complexity introduced here is necessary. Furthermore, the evaluation is lacking, given the incomplete architecture presented. The largest contribution may be the paper's identification of "predicted service" applications; it seems that all internet applications may enter this class by attempting to compute the network capacity available to them on the fly.