draft-ietf-v6ops-cidr-prefix-03.txt   rfc7608.txt 
v6ops Working Group M. Boucadair Internet Engineering Task Force (IETF) M. Boucadair
Internet-Draft France Telecom Request for Comments: 7608 France Telecom
Intended status: Best Current Practice A. Petrescu BCP: 198 A. Petrescu
Expires: November 27, 2015 CEA, LIST Category: Best Current Practice CEA, LIST
F. Baker ISSN: 2070-1721 F. Baker
Cisco Systems Cisco Systems
May 26, 2015 July 2015
IPv6 Prefix Length Recommendation for Forwarding IPv6 Prefix Length Recommendation for Forwarding
draft-ietf-v6ops-cidr-prefix-03
Abstract Abstract
IPv6 prefix length, as in IPv4, is a parameter conveyed and used in IPv6 prefix length, as in IPv4, is a parameter conveyed and used in
IPv6 routing and forwarding processes in accordance with the IPv6 routing and forwarding processes in accordance with the
Classless Inter-domain Routing (CIDR) architecture. The length of an Classless Inter-domain Routing (CIDR) architecture. The length of an
IPv6 prefix may be any number from zero to 128, although subnets IPv6 prefix may be any number from zero to 128, although subnets
using stateless address autoconfiguration (SLAAC) for address using stateless address autoconfiguration (SLAAC) for address
allocation conventionally use a /64 prefix. Hardware and software allocation conventionally use a /64 prefix. Hardware and software
implementations of routing and forwarding should therefore impose no implementations of routing and forwarding should therefore impose no
rules on prefix length, but implement longest-match-first on prefixes rules on prefix length, but implement longest-match-first on prefixes
of any valid length. of any valid length.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This memo documents an Internet Best Current Practice.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 5741.
This Internet-Draft will expire on November 27, 2015. 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/rfc7608.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 3 2. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Normative References . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Informative References . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
Discussions on the 64-bit boundary in IPv6 addressing ([RFC7421]) Discussions on the 64-bit boundary in IPv6 addressing ([RFC7421])
revealed a need for a clear recommendation on which bits must be used revealed a need for a clear recommendation on which bits must be used
by forwarding decision-making processes. However, such a by forwarding decision-making processes. However, such a
recommendation was out of scope for that document. recommendation was out of scope for that document.
Although Section 2.5 of [RFC4291] states "IPv6 unicast addresses are Although Section 2.5 of [RFC4291] states "IPv6 unicast addresses are
aggregatable with prefixes of arbitrary bit-length, similar to IPv4 aggregatable with prefixes of arbitrary bit-length, similar to IPv4
addresses under Classless Inter-Domain Routing" (CIDR, [RFC4632]), addresses under Classless Inter-Domain Routing" (CIDR, [RFC4632]),
there is still a misinterpretation that IPv6 prefixes can be either there is still a misinterpretation that IPv6 prefixes can be either
/127 ([RFC6164]) or any length up to /64. This misinterpretation is /127 ([RFC6164]) or any length up to /64. This misinterpretation is
mainly induced by the 64-bit boundary in IPv6 addressing. mainly induced by the 64-bit boundary in IPv6 addressing.
As discussed in [RFC7421], "the notion of a /64 boundary in the As discussed in [RFC7421], "the notion of a /64 boundary in the
address was introduced after the initial design of IPv6, following a address was introduced after the initial design of IPv6, following a
period when it was expected to be at /80". This evolution of the period when it was expected to be at /80". This evolution of the
IPv6 Addressing architecture, resulting in [RFC4291], and followed IPv6 addressing architecture, resulting in [RFC4291], and followed
with the addition of /127 prefixes for point-to-point links, clearly with the addition of /127 prefixes for point-to-point links, clearly
demonstrates the intent for future IPv6 developments to have the demonstrates the intent for future IPv6 developments to have the
flexibility to change this part of the architecture when justified. flexibility to change this part of the architecture when justified.
It is fundamental not to link routing and forwarding to the IPv6 It is fundamental not to link routing and forwarding to the IPv6
prefix/address semantics [RFC4291]. This document includes a prefix/address semantics [RFC4291]. This document includes a
recommendation for that aim. recommendation in order to support that goal.
Forwarding decisions rely on the longest-match-first algorithm, which Forwarding decisions rely on the longest-match-first algorithm, which
stipulates that, given a choice between two prefixes in the stipulates that, given a choice between two prefixes in the
Forwarding Information Base (FIB) of different length that match the Forwarding Information Base (FIB) of different length that match the
destination address in each bit up to their respective lengths, the destination address in each bit up to their respective lengths, the
longer prefix is used. This document's recommendation (Section 2) is longer prefix is used. This document's recommendation (Section 2) is
that IPv6 forwarding must follow the longest-match-first rule, that IPv6 forwarding must follow the longest-match-first rule,
regardless of prefix length, unless some overriding policy is regardless of prefix length, unless some overriding policy is
configured. configured.
This recommendation does not conflict with the 64-bit boundary for This recommendation does not conflict with the 64-bit boundary for
some IPv6 stateless address autoconfiguration (SLAAC, [RFC4862]) some schemes that based on IPv6 stateless address autoconfiguration
based schemes such as [RFC2464]. Indeed, [RFC7421] clarifies this is (SLAAC) [RFC4862], such as [RFC2464]. Indeed, [RFC7421] clarifies
only a parameter in the SLAAC process and other longer prefix lengths this is only a parameter in the SLAAC process, and other longer
are in operational use (e.g., either manually configured or based prefix lengths are in operational use (e.g., either manually
upon DHCPv6 [RFC3315]). configured or based upon DHCPv6 [RFC3315]).
A historical background of CIDR is documented in [RFC1380] and A historical background of CIDR is documented in [RFC1380] and
Section 2 of [RFC4632]. Section 2 of [RFC4632].
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Recommendation 2. Recommendation
IPv6 implementations MUST conform to the rules specified in IPv6 implementations MUST conform to the rules specified in
Section 5.1 of [RFC4632]. Section 5.1 of [RFC4632].
Decision-making processes for forwarding MUST NOT restrict the length Decision-making processes for forwarding MUST NOT restrict the length
of IPv6 prefixes by design. In particular, forwarding processes MUST of IPv6 prefixes by design. In particular, forwarding processes MUST
be designed to process prefixes of any length up to /128, by be designed to process prefixes of any length up to /128, by
increments of 1. increments of 1.
Policies can be enforced to restrict the length of IP prefixes Policies can be enforced to restrict the length of IP prefixes
advertised within a given domain or in a given interconnection link. advertised within a given domain or in a given interconnection link.
These policies are deployment-specific and/or driven by These policies are deployment specific and/or driven by
administrative (interconnection) considerations. administrative (interconnection) considerations.
3. IANA Considerations 3. Security Considerations
This document does not require any action from IANA.
4. Security Considerations
This document does not introduce security issues in addition to what This document does not introduce security issues in addition to what
is discussed in [RFC4291]. is discussed in [RFC4291].
IPv6 security issues, including operational ones, are discussed in IPv6 security issues, including operational ones, are discussed in
[RFC4942] and [I-D.ietf-opsec-v6]. [RFC4942] and [OPSEC-v6].
5. Acknowledgements
Thanks to Eric Vyncke, Christian Jacquenet, Brian Carpenter, Fernando
Gont, Tatuya Jinmei, Lorenzo Colitti, Ross Chandler, David Farmer,
David Black, and Barry Leiba for their contributions and comments.
Special thanks to Randy Bush for his support.
6. References 4. References
6.1. Normative References 4.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [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>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation (CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, August 2006. Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <http://www.rfc-editor.org/info/rfc4632>.
6.2. Informative References 4.2. Informative References
[I-D.ietf-opsec-v6] [OPSEC-v6] Chittimaneni, K., Kaeo, M., and E. Vyncke, "Operational
Chittimaneni, K., Kaeo, M., and E. Vyncke, "Operational Security Considerations for IPv6 Networks", Work in
Security Considerations for IPv6 Networks", draft-ietf- Progress, draft-ietf-opsec-v6-06, March 2015.
opsec-v6-06 (work in progress), March 2015.
[RFC1380] Gross, P. and P. Almquist, "IESG Deliberations on Routing [RFC1380] Gross, P. and P. Almquist, "IESG Deliberations on Routing
and Addressing", RFC 1380, November 1992. and Addressing", RFC 1380, DOI 10.17487/RFC1380, November
1992, <http://www.rfc-editor.org/info/rfc1380>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998. Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<http://www.rfc-editor.org/info/rfc2464>.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
and M. Carney, "Dynamic Host Configuration Protocol for C., and M. Carney, "Dynamic Host Configuration Protocol
IPv6 (DHCPv6)", RFC 3315, July 2003. for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [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>.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ [RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
Co-existence Security Considerations", RFC 4942, September Co-existence Security Considerations", RFC 4942,
2007. DOI 10.17487/RFC4942, September 2007,
<http://www.rfc-editor.org/info/rfc4942>.
[RFC6164] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti, [RFC6164] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti,
L., and T. Narten, "Using 127-Bit IPv6 Prefixes on Inter- 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>.
[RFC7421] Carpenter, B., Chown, T., Gont, F., Jiang, S., Petrescu, [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S.,
A., and A. Yourtchenko, "Analysis of the 64-bit Boundary Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit
in IPv6 Addressing", RFC 7421, January 2015. Boundary in IPv6 Addressing", RFC 7421,
DOI 10.17487/RFC7421, January 2015,
<http://www.rfc-editor.org/info/rfc7421>.
Acknowledgements
Thanks to Eric Vyncke, Christian Jacquenet, Brian Carpenter, Fernando
Gont, Tatuya Jinmei, Lorenzo Colitti, Ross Chandler, David Farmer,
David Black, and Barry Leiba for their contributions and comments.
Special thanks to Randy Bush for his support.
Authors' Addresses Authors' Addresses
Mohamed Boucadair Mohamed Boucadair
France Telecom France Telecom
Rennes 35000 Rennes 35000
France France
Email: mohamed.boucadair@orange.com Email: mohamed.boucadair@orange.com
skipping to change at page 5, line 34 skipping to change at page 6, line 34
CEA Saclay CEA Saclay
Gif-sur-Yvette, Ile-de-France 91190 Gif-sur-Yvette, Ile-de-France 91190
France France
Phone: +33169089223 Phone: +33169089223
Email: alexandre.petrescu@cea.fr Email: alexandre.petrescu@cea.fr
Fred Baker Fred Baker
Cisco Systems Cisco Systems
Santa Barbara, California 93117 Santa Barbara, California 93117
USA United States
Email: fred@cisco.com Email: fred@cisco.com
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