innovative system offering application developers an extensively flexible group communication model is described. The emergence of process-group environments for distributed computing represents a promising step toward robustness for mission-critical distributed applications. Process groups have a “natural’ ’ correspondence with data or services that have been replicated for availability or as part of a coherent cache. They can be used to support highly available security domains, and group mechanisms fit well with an emerging generation of intelligent network and collaborative work applications.

The Horus system supports a communication architecture that treats protocols as instances of an abstract data type. This approach encourages developers to partition complex protocols into simple microprotocols, each of which is implemented by a protocol layer. Protocol layers can be stacked on top of each other in a variety of ways, at run-time. First, we describe the classes of protocols that can be supported this way. Next, we present the Horus object model that we designed for this technology, and the interface between the layers that makes it all work. We then present an example layer that implements a group membership protocol. Next, we show how, given a set of required properties, an appropriate stack can be constructed. We look at an example stack of protocols, which provides fault-tolerant, totally ordered communication between a group of processes. The work contributes a standard framework for protocol development and experimentation, provides a high performance implementation...

Communication-oriented abstractions such as atomic multicast, group RPC, and protocols for location-independent mobile computing can simplify the development of complex applications built on distributed systems. This paper describes Coyote, a system that supports the construction of highly modular and configurable versions of such abstractions. Coyote extends the notion of protocol objects and hierarchical composition found in existing systems with support for finer-grain objects called micro-protocols that implement individual semantic properties of the target service. A customized service is constructed by selecting micro-protocols based on their semantic guarantees and configuring them together with a standard runtime system to form a composite protocol implementing the service. Micro-protocols within a composite protocol can share data and are executed using an event-driven paradigm that enhances configurability. The overall approach is described and illustrated with exampl...

Abstract. Multicast (group) communications have been widely recognized by current research and industry. Multicast is very useful for various network applications such as distributed (replicated) database, video/audio conference, information distribution and server locations, etc. But design and implementation of such multicast communication systems in networks are complicated tasks, especially when quality of services (QoS) of applications such as real-time and reliability are desired. To quick design and implement multicast communication, good tools are crucial and must be facilitated. This paper presents a novel object-oriented (O-O) QoS driven approach for the quick design and prototyping of multicast communication systems under certain QoS requirements for multicast message transmission and receptions such as real-time, total ordering, atomicity and fault-tolerance, etc.