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A Generic Multicast Transport Serviceto Support Disconnected Operation


Silvano Maffeis, maffeis@acm.org
Walter Bischofberger, bischi@ubilab.ubs.ch
Kai-Uwe M├Ątzel, maetzel@ubilab.ubs.ch

Department of Computer Science, Cornell University,
and UBILAB, Union Bank of Switzerland

Abstract

Many mobile computing applications can profit from process groups and reliable multicast communication to maintain replicated data, but most operating systems available today fail in providing the primitive operations needed by such applications. In this paper we describe a highly configurable, Generic Multicast Transport Service (GTS), which supports the implementation of group-based applications in wide-area settings. GTS is unique in that it offers fault-tolerant, order-preserving multicast on arbitrary communication protocols, including e-mail. As another distinguishing mark, messages can be sent to processes even when they are temporarily unavailable, which permits disconnected operation and mobility. We further propose an object-oriented system design consisting of adaptor objects interconnected to form a protocol tree. Adaptor objects offer a common interface to dissimilar communication protocols, and make it easy to incorporate new protocols into GTS. Currently, GTS is being used in a cooperative software engineering environment and in other projects. GTS is available for anonymous ftp.


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