Quality-of-service in packet networks: basic mechanisms and directions

In this paper, we review the basic mechanisms used in packet networks to su pport Quality-of-Service (QoS) guarantees. We outline the various approache s that have been proposed, and discuss some of the trade-offs they involve. Specifically, the paper starts by introducing the different scheduling and buffer management mechanisms that can be used to provide service different iation in packet networks. The aim is not to provide an exhaustive review o f existing mechanisms, but instead to give the reader a perspective on the range of options available and the associated trade-off between performance , functionality, and complexity. This is then followed by a discussion on t he use of such mechanisms to provide specific end-to-end performance guaran tees. The emphasis of this second part is on the need for adapting mechanis ms to the different environments where they are to be deployed. In particul ar, fine grain buffer management and scheduling mechanisms may be neither n ecessary nor cost effective in high speed backbones, where "aggregate" solu tions are more appropriate. The paper discusses issues and possible approac hes to allow coexistence of different mechanisms in delivering end-to-end g uarantees. (C) 1999 Elsevier Science B.V. All rights reserved.