dce/rpc was commissioned by the open software foundation in a "request for technology" (1993 david chappell). one of the key companies that contributed was apollo computer, who brought in nca - "network computing architecture" which became network computing system (ncs) and then a major part of dce/rpc itself. the naming convention for transports that can be designed (as architectural plugins) and then made available to dce/rpc echoes these origins, e.g. ncacn_np (smb named pipes transport); ncacn_tcp (dce/rpc over tcp/ip) and ncacn_http to name a small number.