Research Issues in Middleware (Bhaskar) Overlay networks for Distributed events Service discovery in the wide-area Service composition Possibly, Hierarchical overlay networks Overlay networks with clusters as nodes To what size can a resilient overlay network scale? RON (MIT) talks about ~50 nodes. This may not be enough for many purposes (e.g., service composition). Can backup-path algorithms be scaled for 100s of nodes? 1000s of nodes? What is the trade-off between latency to recovery and scale of the overlay network? Can a connection-oriented overlay network with route-pinned paths have better latency to recovery than a connection-less overlay network?

Research Issues in Middleware (Bhaskar) Placement of overlay nodes: how can knowledge about the structure of the Internet be used for better resilience? The Internet today mostly has TCP traffic. Most failure, wide-area latency models that exist today are developed in this context. How do things change if there is more streaming video traffic? Does congestion behavior change? CDNs  Distributed preference registry Can the CDN model be extended to managing user preferences for 3G devices? Mostly read-only, slow changes How to move preferences to follow the user?