IPv6 Multicast Address Scopes
RFC 7346

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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RFC 7346 IPv6 Multicast Address Scopes August 2014
Copyright Notice
 Copyright (c) 2014 IETF Trust and the persons identified as the
 document authors. All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
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 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008. The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.
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.
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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
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RFC 7346 IPv6 Multicast Address Scopes August 2014
 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.
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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].
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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
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