A Reliable Multicast Transport layer (connection oriented or connection-less oriented) must provide two major, well-defined classes of functions. The first one called [the Transmi ssi on Fun cti on, must provide a service that ensures message transmission from one host to a set of hosts belonging to a Multicast Group. The Multicast Group is assumed to be known in advance. The second class, called the Reliable Multicast Function, concerns the quality of service, the primitives provided to the user layer and the expected level of reliability. As opposed to the first class, the functions we find here depend on the, aims of applications and their environment constraints. Birman & Joseph [BirJos88] had established a classification of the Reliable Multicast Functions. They assumed that a reliable service of the data transmission is provided by the lower layer.(In the case of ISIS system [Birman88], the reliable transfer service is provided by the TCP/IP layers or by UDP/IP layers and an extra module.). The 3 classes defined in [BirJos88] are the following:(1) Atomic Broadcast Protocols: the Atomicity is one of the major problems in the Multicast protocols. Atomic multicasting means that if a message is sent to N hosts, it must be received by all the N hosts or none. This was solved by protocols based on two-phase ce, mmit algorithms [Gray 78].(2) Ordered Broadcast Protocols: for some distributed applications the order in which messages are received is critical and must be the same at all hosts, eve: a though this order is not determined in advance. Among the protocols that provide this service are the ABCASTpro~ coI described in [BirJos87] and the protocol proposed by [Chang84].