. We formulate a model of extended virtual synchrony that defines a group communication transport service for multicast and broadcast communication in a distributed system. The model extends the virtual synchrony model of the Isis system to support continued operation in all components of a

Abstract: We describe applications of a virtually synchro-nous environment for distributed programming, which underlies a collection of distributed programming tools in the 1SIS2 system. A virtually synchronous environment allows processes to be structured into process groups, and makes events like

A formal definition of strong virtual synchrony, capturing the semantics of virtual synchrony as implemented in Horus, is presented. This definition has the nice property that every message is delivered within the view in which it was sent. However, it is shown that in order to implement strong

We present Optimistic Virtual Synchrony (OVS), a new form of group communication which provides the same capabilities as Virtual Synchrony at better performance. It does so by allowing applications to send messages during periods in which services implementing Virtual Synchrony block. OVS also

View-oriented group communication systems (GCSs) are powerful tools for building distributed applications. Over the past fifteen years, group communication researchers developed a multitude of group communication semantics and implementations. Today, researchers commonly design their group communication algorithms on top of simple existing services such as a network membership service or a reliable FIFO multicast framework. A natural extension of this idea is to implement one set of group communication semantics using another. This approach is not usually utilized due to the expensive overhead of running one set of group communication algorithms on top of another.

We present a protocol for weak virtual synchrony. The protocol is general since it only assumes that the underlying network provides reliable FIFO delivery, which is a common assumption in most, if not all, existing protocols. The protocol incorporates a simple but effective failure detection

In this chapter, we discuss a widely used fault-tolerant data replication model called virtual synchrony. The model responds to two kinds of needs. First, there is the practical question of how best to embed replication into distributed systems. Virtual synchrony defines dynamic process groups

services can be spread over a cluster to exploit parallelism. Servers also use replication to implement high availability and fault tolerance[3] mechanisms, ensure low latency, implement caching, and provide distributed[7] management and control. So virtual Synchrony supports these applications

this paper is not to compare the consistency criterion defined by the transaction model to the consistency criterion defined by the virtual synchrony model. The purpose of the paper is rather to understandand compare the basic mechanisms needed to implementboth models. In all generality

correctness of our mechanisms. We further show, through extensive real-world experiments, that VIRTUS incurs a limited performance penalty compared with best-effort communication. To the best of our knowledge, VIRTUS is the first system to provide virtual synchrony guarantees atop resource-constrained CPS