Enabling Interactive Applications over the Internet

As computers become pervasive in the home and community and homes become better connected, new applications will be deployed over the Internet. Interactive Distributed Applications involve users in multiple locations, across a wide area network, who interact and cooperate by manipulating shared objects. A timely response to user actions, which can potentially update the state of the objects, is an important requirement. Because of the inherent heterogeneity of the environment, traditionally distributed applications are built using technologies like distributed objects. These technologies are built around a central server paradigm which is undesirable because the response time for the actions of interactive users is always subject to communication latencies. Our approach is to extend these technologies with aggressive caching and replication mechanisms without changing the remote object interface to the applications. Thus, caching and replication are done transparently to provide interactive response time and to improve scalability. A flexible caching framework is presented, where objects can be cached in an application specific manner. It provides multiple consistency protocols that enable tradeoffs between the consistency of a cached object’s state at a particular client, and the communication resources available at the client. At runtime, clients can specify their consistency requirements which can vary across different clients. This can be done via a Quality of Service specification interface that is meaningful at the application level. This paper presents the caching framework, its implementation and some preliminary performance results.