RFC 2685 (rfc2685) - Page 2 of 6

Virtual Private Networks Identifier

RFC 2685          Virtual Private Networks Identifier     September 1999


   Virtual Private Dial Networks, and Virtual Private LAN Segments.  In
   addition, numerous drafts and white papers outline methods to be used
   by Service Providers and/or Service Provider customers to enable this
   service.  Solutions may be customer based or network based.  Network
   based solutions may provide connectivity and services at layer 2
   and/or layer 3.  The devices involved in enabling the solution may be
   Customer Premises Equipment (CPE), Service Provider Edge equipment,
   Service Provider Core equipment, or some combination of these.

   While the various methods of VPN service implementation are being
   discussed and debated, there are two points on which there is
   agreement:

    Because a VPN is private, it may use a private address space which
    may overlap with the address space of another VPN or the Public
    Internet.

    A VPN may span multiple IP Autonomous Systems (AS) or Service
    Providers.

   The first point indicates that an IP address only has meaning within
   the VPN in which it exists.  For this reason, it is necessary to
   identify the VPN in which a particular IP address has meaning, the
   "scope" of the IP address.

   The second point indicates that several methods of VPN service
   implementation may be used to provide connectivity and services to a
   single VPN.  Different service providers may employ different
   strategies based on their infrastructure and expertise.  It is
   desirable to be able to identify any particular VPN at any layer and
   at any location in which it exists using the same VPN identifier.

2. Global VPN Identifier

   The purpose of a VPN-ID is to identify a VPN.  This identifier may be
   used in various ways depending on the method of VPN service
   implementation.  For example, the VPN-ID may be included:

    - In a MIB to configure attributes to a VPN, or to assign a physical
      or logical access interface to a particular VPN.

    - In a control or data packet, to identify the "scope" of a private
      IP address and the VPN to which the data belongs.

   It is necessary to be able to identify the VPN with which a data
   packet is associated.  The VPN-ID may be used to make this
   association, either explicitly (e.g. through inclusion of the VPN-ID
   in an encapsulation header [2]) or implicitly (e.g. through inclusion



Fox & Gleeson               Standards Track