2.1 Transport

The User Name Mapping Protocol is a SUNRPC protocol (as specified in [RFC1057]) that runs on TCP/IP using TCP and/or UDP transports, with a well-known program number of MAPSVC_PROGRAM (351455). The User Name Mapping Protocol server registers an available TCP/UDP port with the local portmapper service on startup using the MAPSVC_PROGRAM number for all combinations of TCP, UDP, and protocol versions that the User Name Mapping Protocol server is capable of or configured to accept. User Name Mapping Protocol clients query the SUNRPC portmapper server for the TCP/UDP port number on which the User Name Mapping Protocol is registered and listening for the requested version and transport combination.

Configuration of the portmapper service and port registration is specified in [RFC1057] Appendix A. The User Name Mapping Protocol does not define a configuration interface to the portmapper service.

The User Name Mapping Protocol server provides a procedure-oriented interface to the User Name Mapping Protocol clients. Clients identify the remote procedure by using a combination of a 32-bit program number, a 32-bit version number, and a 32-bit procedure number (as specified in [RFC1057]). The service is stateless; every SUNRPC call is self-contained and does not depend on the previous calls made or previous state of the service.

The User Name Mapping Protocol server accepts all SUNRPC packets with an authentication level of AUTH_NULL, as specified in [RFC1057] section 9.1. Therefore, no authentication information is required by the client.