A Communication-Efficient Causal Broadcast Protocol

International audienceA causal broadcast ensures that messages are delivered to all nodes (processes) preserving causal relation of the messages. In this paper, we propose a causal broadcast protocol for distributed systems whose nodes are logically organized in a virtual hypercube-like topology called VCube. Messages are broadcast by dynamically building spanning trees rooted in the message's source node. By using multiple trees, the contention bottleneck problem of a single root spanning tree approach is avoided. Furthermore , different trees can intersect at some node. Hence, by taking advantage of both the out-of-order reception of causally related messages at a node and these paths intersections, a node can delay to one or more of its children in the tree, the forwarding of the messages whose some causal dependencies it knows that the children in question can not satisfy yet. Such a delay does not induce any overhead. Experimental evaluation conducted on top of PeerSim simulator confirms the communication effectiveness of our causal broadcast protocol in terms of latency and message traffic reduction

Network coding-based reliable wireless multicast

Tohoku University亀山充

Real-Time Causal Message Ordering in Multimedia Systems

In multimedia systems, not only do messages that are sent to and received by multiple sites need to have a consistent order imposed by all sites, but cause and effect relations must be maintained. Causal ordering allows the cause and effect relations of messages to be maintained. This paper presents an algorithm that insures that multimedia data with real-time deadlines are delivered to the application layer in causal order. The algorithm is designed to insure that any message that arrives at a destination site before its deadline will be delivered to the application before the message expires. In addition, by focusing on a form of causal ordering violations caused by "the triangle inequality," this algorithm has a low overhead with respect to the amount of information that must be appended to each message. Keywords: Real-time, causal ordering, multimedia systems, delta-causality, triangle inequality. 1. Introduction Multimedia systems are becoming widespread [2][3][6][7]. They are ..