the realization of a centralized group management server. This is to consider a number of communication group. Each group member is assumed on a different site without a time repository or memory common to the different nodes of the network. The latter therefore form a distributed system. In this case, the server must perform group management operations (creation, destruction insertion of a new member, deletion of a member, delivery of the list of members of a group and their addresses, etc.), and dissemination message providing an order consisting of messages at the reception, ie, all the nodes receive the messages in the same order.