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6man R. Bush
Internet-Draft Internet Initiative Japan
Updates: 4291 (if approved) B. Carpenter
Intended status: Standards Track Univ. of Auckland
Expires: November 24, 2017 F. Gont
SI6 Networks / UTN-FRH
N. Hilliard
INEX
G. Huston
APNIC
C. Morrow
GOOG
J. Snijders
NTT
May 23, 2017
6man N. Bourbaki
Internet-Draft The Intertubes
Updates: 4291 (if approved) July 17, 2017
Intended status: Standards Track
Expires: January 18, 2018
IPv6 is Classless
@ -45,18 +35,7 @@ Status of This Memo
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 24, 2017.
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This Internet-Draft will expire on January 18, 2018.
Copyright Notice
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3
3. Identifier and Subnet Length Statements . . . . . . . . . . . 3
4. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem reinforced by classful addressing . . . . . . . . . . 3
4. Identifier and Subnet Length Statements . . . . . . . . . . . 4
5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
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implementation, which can easily result in serious operational
problems.
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This document also clarifies that IPv6 routing subnets may be of any
length up to 128.
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arguments for operational flexibility in address assignment remain
compelling.
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It is also assumed that the reader understands IPv6 [RFC2460], the IP
Version 6 Addressing Architecture [RFC4291], the proposed changes to
RFC4291 [I-D.ietf-6man-rfc4291bis] and RFC2464
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particular constant. Rather, it should expect any lengths of
interface identifiers.
3. Identifier and Subnet Length Statements
3. Problem reinforced by classful addressing
As IPv6 usage has evolved and grown over in recent years, it has
become evident that it faces several scaling and coordination
problems. These problems are analogous to allocation and
coordination problems that motivated IPv4 CIDR allocation and later
abundant IPv4 PAT, they include:
Address allocation models for specific counts of fixed length
subnets to downstream networks or devices from /48 down to /64 are
based on our imagination of how subnets are or should be allocated
within ipv4 networks.
Hierarchical allocation of fixed-length subnets requires
coordination between lower / intermediate / upper network elements
and has implict assumption that policies and size allocation at
the top of the hierarchy will accomidate all use cases with fixed
lenth subnet allocation.
Coordination with upstream network elements for the allocation of
fixed length subnets reveals topology and intent that may be
private in scope and which amounts to permission to build a
particular topology.
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4. Identifier and Subnet Length Statements
IPv6 unicast interfaces may use any subnet length up to 128 except
for situations where an Internet Standard document may impose a
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Additionally, this document clarifies that a node or router MUST
support routing of any valid network prefix length, even if SLAAC or
other standards are in use, because routing could choose to
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differentiate at a different granularity than is used by any such
automated link local address configuration tools.
4. Recommendations
5. Recommendations
For historical reasons, when a prefix is needed on a link, barring
other considerations, a /64 is recommended [RFC7136].
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recommended (see [RFC8064]) algorithm for selecting stable interface
identifiers [RFC7217] is a parameter, rather than a hardcoded value.
5. Security Considerations
6. Security Considerations
Assuming that nodes employ unpredictable interface identifiers
[RFC7721], the subnet size may have an impact on some security and
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fail to enforce limits on the size of some of the data structures
they employ for communicating with neighboring nodes, such as the
Neighbor Cache. In such cases, the use of smaller subnets forces an
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operational limit on such data structures, thus helping mitigate some
pathological behaviors (such as Neighbor Cache Exhaustion attacks).
6. IANA Considerations
7. IANA Considerations
This document has no IANA Considerations.
8. Authors
The authors of this document are as follows:
Randy Bush, Internet Initiative Japan
Brian Carpenter, University of Auckland
Fernando Gont, SI6 Networks / UTN-FRH
Nick Hilliard, INEX
Geoff Huston, APNIC
Chris Morrow, Google, Inc.
Job Snijders, NTT Communications
9. References
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7. References
7.1. Normative References
9.1. Normative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
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RFC 8064, DOI 10.17487/RFC8064, February 2017,
<http://www.rfc-editor.org/info/rfc8064>.
7.2. Informative References
9.2. Informative References
[I-D.hinden-6man-rfc2464bis]
Crawford, M. and R. Hinden, "Transmission of IPv6 Packets
over Ethernet Networks", draft-hinden-6man-rfc2464bis-02
(work in progress), March 2017.
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[I-D.ietf-6man-rfc4291bis]
Hinden, R. and S. <>, "IP Version 6 Addressing
Architecture", draft-ietf-6man-rfc4291bis-07 (work in
progress), January 2017.
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", draft-ietf-6man-rfc4291bis-09 (work in
progress), July 2017.
[I-D.jinmei-6man-prefix-clarify]
Jinmei, T., "Clarifications on On-link and Subnet IPv6
Prefixes", draft-jinmei-6man-prefix-clarify-00 (work in
progress), March 2017.
[RFC2450] Hinden, R., "Proposed TLA and NLA Assignment Rules",
RFC 2450, December 1998.
[RFC2450] Hinden, R., "Proposed TLA and NLA Assignment Rule",
RFC 2450, DOI 10.17487/RFC2450, December 1998,
<http://www.rfc-editor.org/info/rfc2450>.
[RFC3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
Unicast Address Format", RFC 3587, August 2003.
Unicast Address Format", RFC 3587, DOI 10.17487/RFC3587,
August 2003, <http://www.rfc-editor.org/info/rfc3587>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, August 2006.
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Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <http://www.rfc-editor.org/info/rfc4632>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[RFC6164] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti,
L., and T. Narten, "Using 127-Bit IPv6 Prefixes on Inter-
Router Links", RFC 6164, April 2011.
Router Links", RFC 6164, DOI 10.17487/RFC6164, April 2011,
<http://www.rfc-editor.org/info/rfc6164>.
[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
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Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<http://www.rfc-editor.org/info/rfc7707>.
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[RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
Considerations for IPv6 Address Generation Mechanisms",
RFC 7721, DOI 10.17487/RFC7721, March 2016,
<http://www.rfc-editor.org/info/rfc7721>.
Authors' Addresses
Author's Address
Randy Bush
Internet Initiative Japan
5147 Crystal Springs
Bainbridge Island, Washington 98110
US
Nicolas Bourbaki
The Intertubes
42 Rue du Jour
Sophia-Antipolis ::1
FR
Email: randy@psg.com
Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
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Fernando Gont
SI6 Networks / UTN-FRH
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
Nick Hilliard
INEX
4027 Kingswood Road
Dublin 24
Ireland
Email: nick@inex.ie
Geoff Huston
Email: gih@apnic.net
Chris Morrow
Google, Inc.
1600 Ampitheatre Parkway
Mountain View, California
United States of America
Email: morrowc@google.com
Job Snijders
NTT Communications
Theodorus Majofskistraat 100
Amsterdam 1065 SZ
The Netherlands
Email: job@ntt.net
Email: bourbaki@bogus.com
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