Many applications have a requirement for multidestination delivery. This has implications for naming and access mechanisms: In an language integrated RPC system, some mechanism for collecting replies is needed and either mapping them into an array of results, or providing hooks for voting/selecting a reply. The different models are illustrated in #fnmsgpat#503>. Group communications for applications are not well understood. It would appear that multicast protocols provide a simple packet/message optimisation, but that they do not simplify real group communications problems except for the ;SPM_quot;which of;SPM_quot; type query. Many systems use one to one communication and model groups inside the application[#birman##1#]. Chapter 3 shows how replicated servers are built in this way.

Figure: Message Patterns and IPC

In the most gerneral case, you have both client and server groups. If a server (group) is invoked by a client group then you also need to have mechanisms for collecting invocations and determining which invocations belong to which groups (naming activities).