Internet Engineering Task Force                                 R. Droms
Internet-Draft                                                     Cisco
Updates: RFC 4291 (if approved)                          August 20, 2013
Intended status: Standards Track
Expires: February 21, 2014

                     IPv6 Multicast Address Scopes


   This document updates the definitions of IPv6 multicast scopes.

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1.  Definition of IPv6 Multicast Address Scopes

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   RFC 4291 [RFC4291] defines "scop is a 4-bit multicast scope value
   used to limit the scope of the multicast group." scop 3 is defined as
   "reserved" in RFC 4291.  The multicast protocol specification in
   draft-ietf-roll-trickle-mcast [I-D.ietf-roll-trickle-mcast] desires
   to use multicast scop 3 for transport of multicast traffic scoped to
   a RPL realm (or "domain") [RFC6550].  The use of this scop value is
   to accommodate a multicast scope that is greater than Link-Local but
   is also automatically determined by the network architecture; for
   example, all of the hosts and routers in a multi-link subnet RPL

   The following table updates the definitions in RFC 4291:

   0  reserved

   1  Interface-Local scope

   2  Link-Local scope

   3  Realm-Local scope

   4  Admin-Local scope

   5  Site-Local scope

   6  (unassigned)

   7  (unassigned)

   8  Organization-Local scope

   9  (unassigned)

   A  (unassigned)

   B  (unassigned)

   C  (unassigned)

   D  (unassigned)

   E  Global scope

   F  reserved

   The following paragraph is added as the third paragraph following the
   list of scop values in RFC 4291:

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         Realm-Local scope is the largest scope that is automatically
         configured, i.e., automatically derived from physical
         connectivity or other, non-multicast-related configuration.
         According to <xref target="RFC4007">RFC&nbsp;4007</xref>, 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 inclusion contraint is met.

2.  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"

   Any RFCs that include the definition of a Realm-Local scope will be
   listed in the IANA "IPv6 Multicast Address Scopes" registry.

3.  IANA Considerations

   IANA is asked to establish a sub-registry titled "IPv6 Multicast
   Address Scopes" in the existing "Internet Protocol version 6 (IPv6)
   Multicast Address Allocations" registry.  The "IPv6 Multicast Address
   Scopes" is to be populated with the scope values given in section 1,
   with a note associated with scope 3 listing all RFCs that define
   Realm-Local scoping rules that use scope 3.

4.  Security Considerations

   This document has no security considerations beyond those in RFC 4291

5.  References

5.1.  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.

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5.2.  Informative References

              Hui, J. and R. Kelsey, "Multicast Protocol for Low power
              and Lossy Networks (MPL)", draft-ietf-roll-trickle-
              mcast-04 (work in progress), February 2013.

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

Author's Address

   Ralph Droms
   1414 Massachusetts Avenue
   Boxborough, MA  01719

   Phone: +1 978 936 1674

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