Worth-based multi-category quality-of-service negotiation in distributed object infrastructures

Quality-of-service (QoS) encompasses a wide range of non-functional characteristics, including reliability, security, and performance and is becoming increasingly important in business-critical distributed systems. Such systems are increasingly deployed in open networks, such as the Internet, where resource allocation and load varies highly. To meet QoS requirements in such an environment, systems need to be able to dynamically (re)configure and adapt to changing QoS conditions. This paper describes a model for a QoS negotiation mechanism. The model allows clients and servers in distributed object systems to negotiate for QoS agreements involving multiple QoS categories, such as performance, reliability, security, etc. The model includes both a protocol that enables agents to negotiate and a technique for calculating the worth of alternatives. The protocol handles negotiations involving multiple offers and counter offers. It evaluates an offer based on the absolute requirements for QoS levels and their relative worth to the negotiating systems. The protocol and the worth calculations are part of a QoS negotiation model that involves simultaneous negotiation over multiple QoS categories. We describe how negotiating applications communicate and evaluate offers. In addition, we describe the functions the negotiation mechanism requires from its environment. The protocol has been formally specified and simulated. We are currently investigating implementation approaches and prototypes for the full as well as simplified versions of the described model