Causal Deliveries In Unreliable Networks With Real-Time Delivery Constraints
Roberto Baldoni, Achour Mostéfaoui, Michel Raynal, Projets Adp · 1994
: Causal order states that for any process the order in which it is delivered messages cannot violate the happened-before relation of the corresponding sendings. The aim of this communication abstraction is to cope with the asynchrony of communication channels in distributed systems. This abstraction has been defined for distributed systems without real-time delivery constraints. In this paper we extend this abstraction to cope with unreliable communication networks with real-time delivery constraints: messages have a lifetime, \\Delta, after which their contents can no longer be used, moreover some of them can be lost. This new abstraction, called \\Delta-causal order, requires to deliver as much messages as possible within their lifetime in such a way that these deliveries respect causal order. A simple efficient implementation is proposed. Examples of distributed multimedia real-time applications, in which scheduling messages deliveries respecting \\Delta-causal order is a crucial poin...