Supporting Adaptive Services in a Heterogeneous Mobile Environment

Future computer environments will include mobile computers which will eiUler be disconnected, weakly interconnected by low speed wireless networks such as GSM, or fully inter-connected by high speed networks ranging from Ethernet to ATM. While the transition between networks is currently a heavyweight operation we believe that developments in network interface technology will soon enable mobile computers to dynamically select their network service based on cost and performance requirements. Such flexibility, coupled with tile inherent unreliability of mobile communications, means that system services and applications will be subject to rapid and massive fluctuations in tile quality-of-service provided by their underlying communications infrastructure. In this paper we discuss the design of a distributed systems platform to support tile development of services which are able to tolerate this environment by dynamically adapting to changes in tile available communications quality-of-service.