Internet Engineering Task Force (IETF) R. Droms

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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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
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Contributions published or made publicly available before November
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Without obtaining an adequate license from the person(s) controlling
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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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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: [email protected]

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