Network Working Group B. Carpenter Internet-Draft Univ. of Auckland Intended status: Informational June 13, 2018 Expires: December 15, 2018 The Longest Acceptable Prefix for IPv6 Links draft-carpenter-6man-lap-00 Abstract This document introduces the concept of a Longest Acceptable Prefix for an IPv6 link. Status of This Memo This Internet-Draft is submitted in full conformance with the 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 https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 December 15, 2018. Copyright Notice Copyright (c) 2018 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 (https://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. Carpenter Expires December 15, 2018 [Page 1] Internet-Draft Longest Acceptable Prefix June 2018 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Longest Acceptable Prefix . . . . . . . . . . . . . . . . . . 2 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 6. Informative References . . . . . . . . . . . . . . . . . . . 3 Appendix A. Change log [RFC Editor: Please remove] . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction The IPv6 addressing architecture [RFC4291] clearly separates an address into a routing prefix of length n bits and an interface identifier of length 128-n bits. IPv6 routers are required by BCP 198 [RFC7608] to support any length of routing prefix. For operational reasons, routing prefixes up to 127 bits have been recommended [RFC6164]. Stateless Address Autoconfiguration (SLAAC) [RFC4862] requires a fixed prefix length for each Layer 2 medium, and for largely historical reasons [RFC7136] this has been fixed for all media as 64 bits by the addressing architecture. Efforts to update the addressing architecture [I-D.ietf-6man-rfc4291bis] have shown that there are contradictory opinions about retaining this fixed length for all purposes, not just for SLAAC. See for example [I-D.bourbaki-6man-classless-ipv6]. This document does not aim to rehash those opinions and the arguments behind them. Its purpose is to propose simple terminology to make the discussion easier. 2. Longest Acceptable Prefix As noted above, any prefix length up to /128 is treated identically by routing protocols. However, for a given network, end site, or link, there always exists a Longest Acceptable Prefix (LAP), whose length is locally determined. Currently, a site or link that uses SLAAC has a LAP of /64, and will not work with a longer one. A point-to-point link may have a LAP of /127, according to [RFC6164]. Situations in which other LAPs might be used should be defined in other documents. Carpenter Expires December 15, 2018 [Page 2] Internet-Draft Longest Acceptable Prefix June 2018 3. Security Considerations As noted in the Security Considerations of [I-D.ietf-6man-rfc4291bis], the length of an interface identifier, and therefore the length of a LAP, have important implications for privacy. Proposals for adopting LAPs longer than /64 must take this into account. 4. IANA Considerations This document makes no request of the IANA. 5. Acknowledgements Useful comments were received from ... 6. Informative References [I-D.bourbaki-6man-classless-ipv6] Bourbaki, N., "IPv6 is Classless", draft-bourbaki-6man- classless-ipv6-03 (work in progress), March 2018. [I-D.ietf-6man-rfc4291bis] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", draft-ietf-6man-rfc4291bis-09 (work in progress), July 2017. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . [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, DOI 10.17487/RFC6164, April 2011, . [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, February 2014, . Carpenter Expires December 15, 2018 [Page 3] Internet-Draft Longest Acceptable Prefix June 2018 [RFC7608] Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix Length Recommendation for Forwarding", BCP 198, RFC 7608, DOI 10.17487/RFC7608, July 2015, . Appendix A. Change log [RFC Editor: Please remove] draft-carpenter-6man-lap, 2018-06-13: Initial version Author's Address Brian Carpenter Department of Computer Science University of Auckland PB 92019 Auckland 1142 New Zealand Email: brian.e.carpenter@gmail.com Carpenter Expires December 15, 2018 [Page 4]