IPv6 Prefix Length Recommendation for Forwarding
RFC 7608
Document | Type |
RFC - Best Current Practice
(July 2015; No errata)
Also known as BCP 198
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|
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Authors | Mohamed Boucadair , Alexandre Petrescu , Fred Baker | ||
Last updated | 2015-10-14 | ||
Replaces | draft-boucadair-6man-prefix-routing-reco | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Lee Howard | ||
Shepherd write-up | Show (last changed 2015-02-17) | ||
IESG | IESG state | RFC 7608 (Best Current Practice) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Joel Jaeggli | ||
Send notices to | (None) | ||
IANA | IANA review state | IANA OK - No Actions Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) M. Boucadair Request for Comments: 7608 France Telecom BCP: 198 A. Petrescu Category: Best Current Practice CEA, LIST ISSN: 2070-1721 F. Baker Cisco Systems July 2015 IPv6 Prefix Length Recommendation for Forwarding Abstract IPv6 prefix length, as in IPv4, is a parameter conveyed and used in IPv6 routing and forwarding processes in accordance with the Classless Inter-domain Routing (CIDR) architecture. The length of an IPv6 prefix may be any number from zero to 128, although subnets using stateless address autoconfiguration (SLAAC) for address allocation conventionally use a /64 prefix. Hardware and software implementations of routing and forwarding should therefore impose no rules on prefix length, but implement longest-match-first on prefixes of any valid length. Status of This Memo This memo documents an Internet Best Current Practice. 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 BCPs 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/rfc7608. Boucadair, et al. Best Current Practice [Page 1] RFC 7608 July 2015 Copyright Notice Copyright (c) 2015 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents 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 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Normative References . . . . . . . . . . . . . . . . . . 4 4.2. Informative References . . . . . . . . . . . . . . . . . 4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Discussions on the 64-bit boundary in IPv6 addressing ([RFC7421]) revealed a need for a clear recommendation on which bits must be used by forwarding decision-making processes. However, such a recommendation was out of scope for that document. Although Section 2.5 of [RFC4291] states "IPv6 unicast addresses are aggregatable with prefixes of arbitrary bit-length, similar to IPv4 addresses under Classless Inter-Domain Routing" (CIDR, [RFC4632]), there is still a misinterpretation that IPv6 prefixes can be either /127 ([RFC6164]) or any length up to /64. This misinterpretation is mainly induced by the 64-bit boundary in IPv6 addressing. As discussed in [RFC7421], "the notion of a /64 boundary in the address was introduced after the initial design of IPv6, following a period when it was expected to be at /80". This evolution of the IPv6 addressing architecture, resulting in [RFC4291], and followed with the addition of /127 prefixes for point-to-point links, clearly demonstrates the intent for future IPv6 developments to have the flexibility to change this part of the architecture when justified. Boucadair, et al. Best Current Practice [Page 2] RFC 7608 July 2015 It is fundamental not to link routing and forwarding to the IPv6 prefix/address semantics [RFC4291]. This document includes a recommendation in order to support that goal. Forwarding decisions rely on the longest-match-first algorithm, which stipulates that, given a choice between two prefixes in the Forwarding Information Base (FIB) of different length that match theShow full document text