Internet Engineering Task Force (IETF)                          R. Droms
Request for Comments: 7346                                         Cisco
Updates: 4007, 4291                                          August 2014
Category: Standards Track
ISSN: 2070-1721

                     IPv6 Multicast Address Scopes

Abstract

   This document updates the definitions of IPv6 multicast scopes and
   therefore updates RFCs 4007 and 4291.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7346.

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1.  Introduction

   RFC 4291 [RFC4291] defines "scop" as "a 4-bit multicast scope value
   used to limit the scope of the multicast group" and defines "scop 3"
   as "reserved".  The multicast protocol specification in [MPL] desires
   to use multicast scop 3 to transport multicast traffic scoped to a
   network of nodes connected in a mesh.  This scop value is used to
   accommodate a multicast scope that is greater than Link-Local but is
   also automatically determined by the network architecture.

2.  Definition of IPv6 Multicast Address Scopes (Updates RFC 4291)

   The following table updates the definitions in [RFC4291]:

      +------+--------------------------+-------------------------+
      | scop | NAME                     | REFERENCE               |
      +------+--------------------------+-------------------------+
      |  0   | Reserved                 | [RFC4291], RFC 7346     |
      |  1   | Interface-Local scope    | [RFC4291], RFC 7346     |
      |  2   | Link-Local scope         | [RFC4291], RFC 7346     |
      |  3   | Realm-Local scope        | [RFC4291], RFC 7346     |
      |  4   | Admin-Local scope        | [RFC4291], RFC 7346     |
      |  5   | Site-Local scope         | [RFC4291], RFC 7346     |
      |  6   | Unassigned               |                         |
      |  7   | Unassigned               |                         |
      |  8   | Organization-Local scope | [RFC4291], RFC 7346     |
      |  9   | Unassigned               |                         |
      |  A   | Unassigned               |                         |
      |  B   | Unassigned               |                         |
      |  C   | Unassigned               |                         |
      |  D   | Unassigned               |                         |
      |  E   | Global scope             | [RFC4291], RFC 7346     |
      |  F   | Reserved                 | [RFC4291], RFC 7346     |
      +------+--------------------------+-------------------------+

   The following change is applied to Section 2.7 of [RFC4291].

   OLD:

      Admin-Local scope is the smallest scope that must be
      administratively configured, i.e., not automatically derived from
      physical connectivity or other, non-multicast-related
      configuration.

   NEW:

      Interface-Local, Link-Local, and Realm-Local scope boundaries are
      automatically derived from physical connectivity or other non-
      multicast-related configurations.  Global scope has no boundary.
      The boundaries of all other non-reserved scopes of Admin-Local or
      larger are administratively configured.  For reserved scopes, the
      way of configuring their boundaries will be defined when the
      semantics of the scope are defined.

      According to RFC 4007 [RFC4007], the zone of a Realm-Local scope
      must fall within zones of larger scope.  Because the zone of a
      Realm-Local scope is configured automatically while the zones of
      larger scopes are configured manually, care must be taken in the

      definition of those larger scopes to ensure that the inclusion
      constraint is met.

      Realm-Local scopes created by different network technologies are
      considered to be independent and will have different zone indices
      (see Section 6 of [RFC4007]).  A router with interfaces on links
      using different network technologies does not forward traffic
      between the Realm-Local multicast scopes defined by those
      technologies.

3.  Definition of Realm-Local Scopes

   The definition of any Realm-Local scope for a particular network
   technology should be published in an RFC.  For example, such a scope
   definition would be appropriate for publication in an "IPv6-over-foo"
   RFC.

   Any RFCs that include the definition of a Realm-Local scope will be
   added to the IANA "IPv6 Multicast Address Scopes" registry under the
   Realm-Local scope entry, and those specifications must include such a
   request in their IANA Considerations.

   Section 5 of this document gives the definition of scop 3 for IEEE
   802.15.4 [IEEE802.15.4] networks.

4.  Definition of Automatic and Administratively Configured Scopes
    (Updates RFC 4007)

   Section 5 of RFC 4007 [RFC4007] and Section 2.7 of RFC 4291 [RFC4291]
   disagree on the way in which multicast scop 3 is configured.  To
   resolve that disagreement, the last bullet in the list in Section 5
   of [RFC4007] is updated as follows:

   OLD:

   o  The boundaries of zones of a scope other than interface-local,
      link-local, and global must be defined and configured by network
      administrators.

   NEW:

   o  The boundaries of zones of a scope are defined by the IPv6
      addressing architecture [RFC4291] and updated by RFC 7346.

5.  Definition of Realm-Local Scope for IEEE 802.15.4

   When used in an IP-over-IEEE802.15.4 network, scop 3 is defined to
   include all interfaces sharing a Personal Area Network Identifier
   (PAN ID).

6.  IANA Considerations

   IANA has established a sub-registry titled "IPv6 Multicast Address
   Scopes" in the existing "IPv6 Multicast Address Space Registry".  The
   new registry has been populated with the scop values given in
   Section 2.  New definitions for scop values will be made following
   the "IETF Review" policy [RFC5226].

   For each future RFC that defines a Realm-Local scope for new network
   technologies (scop 3), IANA will add a reference to the defining
   document in the "IPv6 Multicast Address Scopes" registry.  Such RFCs
   are expected to make an explicit request to IANA for inclusion in the
   registry.

   IANA has included a note on the top of the "IPv6 Multicast Address
   Scopes" registry:

      The definition of any Realm-Local scope for a particular network
      technology should be published in an RFC.  For example, such a
      scope definition would be appropriate for publication in an 'IPv6-
      over-foo' RFC.

      Any RFCs that define a Realm-Local scope will be listed in this
      registry as an additional reference in the Realm-Local scope
      entry.  Such RFCs are expected to make an explicit request to IANA
      for inclusion in this registry.

7.  Acknowledgments

   Robert Cragie, Kerry Lynn, Jinmei Tatuya, Dave Thaler, and Stig
   Venaas all contributed text and/or review to ensure that the updates
   to RFC 4007 and RFC 4291 are correct.

8.  Security Considerations

   This document has no security considerations beyond those in RFC 4007
   [RFC4007] and RFC 4291 [RFC4291].

9.  References

9.1.  Normative References

   [RFC4007]  Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
              B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
              March 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

9.2.  Informative References

   [IEEE802.15.4]
              IEEE Computer Society, "IEEE Std. 802.15.4-2006", October
              2006.

   [MPL]      Hui, J. and R. Kelsey, "Multicast Protocol for Low power
              and Lossy Networks (MPL)", Work in Progress, April 2014.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

Author's Address

   Ralph Droms
   Cisco
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   Phone: +1 978 936 1674
   EMail: rdroms.ietf@gmail.com