RFC 1661 (rfc1661) - Page 2 of 52

The Point-to-Point Protocol (PPP)

RFC 1661                Point-to-Point Protocol                July 1994


      respective network-layer protocols.  These NCPs are defined in
      companion documents.

   Configuration

      It is intended that PPP links be easy to configure.  By design,
      the standard defaults handle all common configurations.  The
      implementor can specify improvements to the default configuration,
      which are automatically communicated to the peer without operator
      intervention.  Finally, the operator may explicitly configure
      options for the link which enable the link to operate in
      environments where it would otherwise be impossible.

      This self-configuration is implemented through an extensible
      option negotiation mechanism, wherein each end of the link
      describes to the other its capabilities and requirements.
      Although the option negotiation mechanism described in this
      document is specified in terms of the Link Control Protocol (LCP),
      the same facilities are designed to be used by other control
      protocols, especially the family of NCPs.



1.1.  Specification of Requirements

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.

   MUST      This word, or the adjective "required", means that the
             definition is an absolute requirement of the specification.

   MUST NOT  This phrase means that the definition is an absolute
             prohibition of the specification.

   SHOULD    This word, or the adjective "recommended", means that there
             may exist valid reasons in particular circumstances to
             ignore this item, but the full implications must be
             understood and carefully weighed before choosing a
             different course.

   MAY       This word, or the adjective "optional", means that this
             item is one of an allowed set of alternatives.  An
             implementation which does not include this option MUST be
             prepared to interoperate with another implementation which
             does include the option.






Simpson