Structuring QoS-Supporting Services with

Abstract. While middleware platforms have been established in besteffort environments nowadays, support for QoS-sensitive services is still found lacking. More specifically, due to the high diversity of QoS requirements, the abstractions provided for QoS-unaware services cannot be maintained and the developer has to face the difficulties of low-level networking in heterogeneous environments again. In this paper, we therefore propose the notion of smart proxies as an effective means for making the use of QoS-sensitive services for the client-application developer as comfortable as the use of QoS-unaware services. This is achieved without imposing restrictions on the internal mechanisms and protocols used by an QoS-sensitive service to guarantee an agreed on level of QoS. Basically, smart proxies encapsulate service-specific code which is downloaded dynamically to the client during binding establishment. The benefits of this model are discussed in general and exemplified in a case study.