Many distributed and parallel applications can make good use of broadcast communication. In this paper we present a (software) protocol that simulates reliable broadcast, even on an unreliable network. Using this protocol, application programs need not worry about lost messages. Recovery of communication failures is handled automatically and transparently by the protocol. In normal operation, our protocol is more efficient than previously published reliable broadcast protocols. An initial implementation of the protocol on 10 MC68020 CPUs connected by a 10 Mbit/sec Ethernet performs a reliable broadcast in 1.5 msec.

Increasing use of distributed systems, with the corresponding decentralization of activities, stimulates the need for structuring those activities around groups of participants, for reasons of consistency, userfriendliness, performance and dependability. Two very diverse fields illustrate this trend: computer supported cooperative group working; distributed computer control. This paper discusses ways for structuring systems and defining building blocks for group-oriented activity. It is felt that efficient abstractions for the design of highly distributed applications should be structured around concepts like object groups. Furthermore, the group concept should pervade the whole architecture, from network multicasting, to group communications and management, and fundamental synchronisation paradigms. Emerging technology will help materialize these concepts. Introduction Increasing use of distributed systems, with the corresponding decentralization of activities, stimulates the need f...

Increasing use of distributed systems, with the corresponding decentralisation, stimulates the need for structuring activities around groups of participants, for reasons of consistency, user-friendliness, performance and dependability. Although there is a significant number of group communication protocols in the literature, they are penetrating too slowly in operating systems technology. Two important reasons are: the literal interpretation generally made of the end-to-end argument, and the lack of a layer mapping end-user needs (management of replication, competition, cooperation and group membership) into what is generally provided by the communication layer: agreement and order properties. The paper discusses both problems, proposing ways for structuring systems and defining building blocks for group-oriented activity, using concepts like object groups. It suggests that the group concept should pervade the whole architecture, from network multicasting, to group communications and m...

Multipoint communication allows information transfer within a group of peer entities and is becoming more and more relevant in distributed environments. For distributed or replicated data, it ensures an efficient communication without overloading the network. Multicast is defined as a subset of multipoint where a single sender transmits data to a group of receivers. Several classes of multicast services have been defined to respond to application requirements in terms of efficiency, reliability, and performance. This paper surveys protocol functions and mechanisms for reliable multicast data transmission. A multicast protocol basically consists of a three phase protocol (data transmission, acknowledgment, and validation), which can be implemented in various ways. This paper characterizes reliability in the studied protocols. Functionalities and implementation mechanisms are analyzed. The paper concludes with a statement on current developments in multicast Transport protocol and servic...

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