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A survey on the design, applications, and enhancements of application-layer overlay networks

This article presents a survey of recent advancements in application-layer overlay networks. Some of the most important applications that have been proposed for overlays include multicast, QoS support, denial-of-service (DoS) defense, and resilient routing. We look at some of the important approaches proposed for these applications and compare the advantages and disadvantages of these approaches. We also examine some of the enhancements that have been proposed in overlay topology design, enhanced routing performance, failure resistance, and the issues related to coexistence of overlay and native layers in the Internet. We conclude the article with a comment on the purist vs pluralist argument of overlay networks that has received much debate recently. Finally, we propose a new deployment model for service overlays that seeks to interpose between these two approaches.