A remote procedure is uniquely identified by the triple:
The program number identifies a group of related remote procedures, each of which has a unique procedure number.
A program can consist of one or more versions. Each version consists of a collection of procedures that are available to be called remotely. Version numbers enable multiple versions of an RPC protocol to be available simultaneously.
Each version contains a number of procedures that can be called remotely. Each procedure has a procedure number.
Program and Procedure Numbers lists the range of values and their significance and tells you how to have a program number assigned to your RPC program. A list of mappings of RPC service name to program number is available in the RPC network database /etc/rpc.