1. Conventions Used in this Document

   "C:" and "S:" in examples show lines sent by the client and server
   respectively.

   The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
   this document when typed in uppercase are to be interpreted as
   defined in "Key words for use in RFCs to Indicate Requirement Levels"
   [KEYWORDS].