Reliable publish/subscribe middleware for time-sensitive internet-scale applications

Federating mission critical systems over wide-area networks still represents a challenging issue. For example, it is hard to assure both reliability and timeliness in a hostile environment such as Internet. The publish/subscribe (pub/sub) interaction model is a promising solution for scalable data dissemination over wide-area networks. Nevertheless, currently available pub/sub systems lack efficient support to achieve both reliability and timeliness in unreliable scenarios. This paper describes an innovative approach to fill this gap making three contributions. First, a cluster-based peer-to-peer organization is introduced to handle a large number of publishers and subscribers. Second, the cluster coordinator is replicated to mask process crashes and to preserve cluster connectivity toward the outside world. Third, multiple-tree redundancy is applied to tolerate link crashes thereby minimizing unpredictability in the delivery time. We present a simulation-based evaluation to assess the effectiveness of our approach in an unreliable setting. This study indicates that our approach enforces the reliability of event delivery without affecting its timeliness.