MOve: Design and Evaluation of a Malleable Overlay for Group-Based Applications

While peer-to-peer overlays allow distributed applications to scale and tolerate failures, most structured and unstructured overlays in literature today are inflexible from the application viewpoint. The application thus has no first-class control on the overlay structure. This paper proposes the concept of an application-malleable overlay, and the design of the first malleable overlay which we call MOve. MOve is targeted at group- based applications, e.g., collaborative applications. In MOve, the communication characteristics of the distributed application using the overlay can influence the overlay's structure itself, with the twin goals of (1) optimizing the application performance by adapting the overlay, while also (2) retaining the large scale and fault tolerance of the overlay approach. Besides neighbor list membership management, MOve also contains algorithms for resource discovery, update propagation, and churn-resistance. The emergent behavior of the implicit mechanisms used in MOve manifests as follows: when application communication is low, most overlay links keep their default configuration; however, as application communication characteristics become more evident, the overlay gracefully adapts itself to the application. We validate MOve using simulations with group sizes that are fixed, uniform, exponential and PlanetLab-based (slices), as well as churn traces and two sample management-based applications.