Adaptive information distribution for dynamic sets using multicast push and pull

Abstract

When developing applications in the area of ubiquitous computing, the developer often does not know at design time which and how many devices will be available at runtime when the user deploys the application in his personal environment. To tackle this problem, we proposed a new programming abstraction called dynamic sets in previous work. A dynamic set allows an application to interact transparently with a set of remote objects in the same way it interacts with a single object. The developer programs against a proxy that replicates the calls to the objects and aggregates the return values. While dynamic sets make application development easier and more flexible, efficiency problems can arise when an application is calling proxy methods with high frequency as if the object was local (since the calls are replicated to all members of the dynamic set). In this paper, we propose adaptive heuristics that tackle this problem for getter methods returning information about the objects' state. The heuristics use unicast and multicast communication and dynamically switch between pull (application requests update from object) and push (object sends update to application) depending on the getter rates of applications and the setter rates of objects to optimize communication costs. After describing the basic interaction patterns and presenting the details of our heuristics, we present the results of a comprehensive evaluation based on discrete event simulations. The results show that our heuristics effectively reduce communication costs although they operate on the application layer and, thus, have no detailed knowledge about the physical network topology.