Adaptive Quality-of-Service Support in Heterogeneous Networks: Results of a Trans-European Experiment

The increasing availability of high-speed networks has served as an enabling technology for applications such as networked multimedia, where a mix of information types can be retrieved from decentralized information stores and presented at a user's workstation. Such transfers work best when a guaranteed amount of network capacity is presented to the application fetching the data. Unfortunately, as the storage of information becomes more decentralized, and as the load on individual information sources and sinks increase, it is often difficult to obtain service guarantees for the duration of a lengthy information exchange-especially when the information access is determined by the dynamic behaviour of users, such as is present in a hypermedia application environment. This project defined an experiment in providing adaptive, runtime control over hypermedia information in a wide-area network. The purpose of the experiment was to determine the adaptive control mechanisms required to provide decentralized access to complex data in an unpredictable networked environment. The unpredictability of the environment may be caused by transient reallocations of network bandwidth, overloading of network servers or reliability problems within the communications infrastructure. In the following sections, we describe the planned and encountered: environment, method and expected results of a series of quality-of-service experiments conducted over moderate-bandwidth links between various European network organizations. We then discuss problems in producing the planned results. We conclude with a travel/expense summary for the project.