Delta-Causality and epsilon-delivery for wide-area group communications

In distributed applications, a group of multiple processes cooperate by exc hanging messages. It is critical to support the group of application proces ses enough quality of service (QoS) including the ordered delivery of messa ges. The delay time and the message loss ratio are significant QoS paramete rs. In Internet applications, the delay time and the loss ratio are si,sign ificantly different in different communication channels. We define a novel causality named Delta*-causality among the messages to hold in the world-wi de environment. We discuss how to transmit messages to the destination proc esses and how to resolve message loss and delay supporting the Delta*-causa lity, given the requirements of delay time and message loss ratio. (C) 2000 Elsevier Science B.V. All rights reserved.