D. Andersen. H. Balakrishnan, F. Kaashoek, R. Morris, "Resilient Overlay Networks," 18th Symposium on Operating Systems Principles, (December 2001).Resilient Overlay Network is an architecture that allows distributed Internet applications to detect and recover from path outages and periods of degraded performance within a matter of seconds. The idea is that by building an application level overlay network, we can achieve an increase in performance as well as reliability. The overall concept of RON involves a small group of nodes spread across the network in multiple ISPs. They keep pinging each other and help in creating a global state of 'link healths' (similar to link state concept) and decide to overlay packets between hosts either directly or through intermediate host(s) based on the global link health information. This helps in circumventing policy restrictions imposed by ISPs, helps it in adapting to network conditions or helps in customizing to various applications such as video/voice etc.
Overall, the analysis was definitely encouraging. It was observed that overlay network reacted to failures in a matter of seconds as opposed to BGP which takes many minutes before restoring original flow. An interesting phenomenon was observed that RON paths were actually shorter that BGP paths. My only point of critique/concern with this paper would be as to how feasible would be its wide deployment? Wouldn't the ISPs be concerned about the fact that overlay networks mess with their traffic engineering? Wouldn't this make them take steps against it? Further, issues involving large scale deployment (and probably resulting congestion due to control place information) aren't really tackled in the paper. It would be interesting to discuss these aspects in class.
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