AVCast: New approaches for implementing generic availability-dependent reliability predicates for multicast receivers

Today's large-scale distributed systems consist of collections of nodes, each of which has its own availability characteristics - a phenomenon sometimes called churn. This availability variation across nodes is often a hindrance to achieving reliability and performance for distributed applications such as multicast. This paper looks into utilizing and leveraging availability information in order to implement arbitrary predicates that specify availability-dependent message reliability for multicast receivers. An application (e.g., a publish-subscribe system) may want to scale the multicast message reliability at each receiver according to that receiver's availability (in terms of the fraction of time that receiver is online)- different options are that the reliability is independent of the availability, proportional to it, or an arbitrary function of it, etc.We propose several gossipbased algorithms to support an arbitrary class of such predicates. These techniques rely on each node's availability being monitored in a distributed manner by a small group of other nodes in such a way that the monitoring load is evenly distributed in the system. Our techniques are light-weight, scalable, and are spaceand time- efficient. We analyze our algorithms and evaluate them experimentally by injecting availability traces collected from real peer-to-peer systems.