RFC: Dial String Parameter for Session Initiation Protocol Resource ID (2007)

I found this in an unrelated search. It looks kinda interesting.

Actual title: "Dial String Parameter for the Session Initiation Protocol Uniform Resource Identifier"

Explainer from link:

" Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   RFC 3966 explicitly states that 'tel' URIs may not represent a dial
   string.  That leaves no way specify a dial string in a standardized
   way.  Great confusion exists with the SIP URI parameter "user=phone",
   and specifically, if it can represent a dial string.  This memo
   creates a new value for the user parameter "dialstring", so that one
   may specify "user=dialstring" to encode a dial string as a 'sip:' or
   'sips:' URI.