RFC 5531, "RPC: Remote Procedure Call Protocol Specification Version 2", May 2009Source of RFC: nfsv4 (tsv)
Errata ID: 4099
Reported By: anatoly techtonik
Date Reported: 2014-09-05
Rejected by: Martin Stiemerling
Date Rejected: 2015-12-16
Throughout the document, when it says:
This document describes the Open Network Computing (ONC) Remote Procedure Call (RPC) version 2 protocol as it is currently deployed and accepted.
The document doesn't describe UDP and TCP port number 111, which is used to make initial connection for RCP services discovery and port mapping. Port mapping is an essential part of protocol without which ONC RPC services can't work.
RFC doesn't describe 111 is hardcoded number or can be changed. Doesn't say that servers typically listen on both UDP and TCP 111 (Linux nfs-kernel-server).
This RFC is solely describing the RPC protocol and not the underlying transport that might be used.