Best-eeort versus Reservations: a Simple Comparative Analysis

The current Internet only ooers best-eeort service. In recent years much research eeort, and IETF standardization activity, has been devoted to extending the Internet architecture to support reservations. However, the wisdom of such an extension continues to remain in doubt. Using a simple analytical model, this paper addresses the following question: Should the Internet retain its best-eeort-only architecture, or should it adopt one that is reservation-capable? We characterize the diierences between reservation-capable and best-eeort-only networks in terms of application performance and total welfare. Our analysis does not yield a deenitive answer to the question we pose, since it would necessarily depend on unknowable factors such as the future cost of network bandwidth and the nature of the future traac load. However, our model does reveal some interesting phenomena. First, in some circumstances, the amount of incremental bandwidth needed to make a best-eeort-only network perform as well as a reservation capable one diverges as capacity increases. Second, in some circumstances reservation-capable networks retain signiicant advantages over best-eeort-only networks, no matter how cheap bandwidth becomes. Lastly, we nd bounds on the maximum performance advantage a reservation-capable network can achieve over best-eeort architectures. The views expressed here do not reeect the position or policy of the U.S. government. We would like to acknowledge the crucial contributions made in the early stages of this project by Deborah Estrin and Subramaniam Vincent.