Efficacy of techniques for responsiveness in a wide-area publish/subscribe system

As the multiplicity of organizational domains often span across nations, or even continents, the need for federated communications across domains becomes paramount. Consequently, messaging middleware has become critical towards enabling cross-domain, wide-area federations. Cross-domain federation has placed increased emphasis on the need for the messaging system to provide Quality of Service (QoS), particularly with respect to responsive delivery of messages. Responsiveness, or timely delivery of messages, is critical in real-world services, such as a smart utility grid system. This study explores the efficacy of providing responsiveness in wide-area publish/subscribe messaging by evaluating several key techniques for managing latency. Specifically, this paper evaluates the following techniques: proactive best-path routing, reactive QoS-aware routing, and multipath routing. We present Harmony, a QoS-aware publish/subscribe middleware system, that adapts these techniques in order to provide responsive and high availability messaging. This study seeks to provide an in-depth understanding of how different techniques to manage responsiveness affect the end-to-end performance under various network conditions.