A Generic Multicast Transport Service to Support Disconnected Operation

Many mobile computing applications can proot 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 conngurable, Generic Multicast Transport Service (GTS), which supports the implementation of group-based applications in wide-area settings. GTS is unique in that it ooers 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 ooer 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.