6MAN Working Group G. Mishra Internet-Draft Verizon Inc. Updates: RFC2464, RFC4291, RFC4861, RFC4862, D. Shytyi RFC7136, RFC8273 (if approved) 6WIND Intended status: Standards Track A. Petrescu Expires: 9 January 2025 CEA, LIST N. Kottapalli D. Mudric Ciena 8 July 2024 SLAAC Prefixes with Variable Interface ID (IID) draft-mishra-6man-variable-iids-00 Abstract This draft proposes the use of a longer prefixes in PIO for SLAAC allowing a maximum prefix length of /80 with an IID of 48 bits. This would eliminate the race to the bottom concerns. This implementation uses the RA/PIO bits to carry the variable IID to ensure backwards compatibility. In the past, various IPv6 addressing models have been proposed based on a subnet hierarchy embedding a 64-bit prefix. The last remnant of IPv6 classful addressing is a inflexible interface identifier boundary at /64. This document proposes flexibility to the fixed position of that boundary for interface addressing. 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 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/. Mishra, et al. Expires 9 January 2025 [Page 1] Internet-Draft Variable IID July 2024 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 9 January 2025. Copyright Notice Copyright (c) 2024 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Modified Procedures . . . . . . . . . . . . . . . . . . . . . 3 4. Operational Considerations . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 9.1. Normative References . . . . . . . . . . . . . . . . . . 5 9.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction The lowest common denominator method of configuration for IPv6 nodes is SLAAC [RFC4862], which is carefully designed to allow any prefix length and any interface identifier (IID) length, provided that they do not total more than 128 bits. Until now, specifications of "IPv6 over foo" mappings, starting with [RFC2464], have specified an IID length of 64 bits, consistent with the value specified by [RFC4291]. Mishra, et al. Expires 9 January 2025 [Page 2] Internet-Draft Variable IID July 2024 This document allows a router to announce an IID length other than 64 on a given link, and updates RFC [RFC4291], [RFC2464] (and numerous other "IPv6 over foo" documents TBD), and [RFC4862] accordingly. It extends [RFC4861] by defining a new "IID length" mechanism in RA messages. 2. Terminology Terminolgoy used in defining the IPv6-Only Edge specification. Modified Host: Supports this specification Unmodified Host: Does not support this specification 3. Modified Procedures The predefined IID length specified by [RFC4291], [RFC2464], etc. is used to configure the link-local IPv6 address of a node exactly as described in [RFC4862]. On a link where variable IID length is not supported, the predefined IID length will continue to be used to configure all other addresses using SLAAC. On a link where variable IID length is supported, each modified router will include an "IID length" indication in every RA/PIO message with the A bit set. This will override the value defined in [RFC2464] (etc.) and in [RFC4291], for the prefix concerned. In this variable IID specification it is recommended to put the IID length in the 6 bits of the Reserved2 field of the PIO. 0b000000 would mean 64, i.e. no change and backwards compatible. Any other value would define an IID length in bits. Values less than 48 (0b110000) are NOT RECOMMENDED. Values greater than 64 are impossible. (Note: Reserved1 is not available - see [RFC8425].) When a modified node receives an "IID length" less than 64, it will use that value instead of the default for all unicast address autoconfiguration under that prefix, except link-local. 4. Operational Considerations - Unmodified hosts and unmodified routers: no change, all use 64-bit IIDs. Mishra, et al. Expires 9 January 2025 [Page 3] Internet-Draft Variable IID July 2024 - Modified hosts and unmodified routers: no change, all use 64-bit IIDs. - Modified hosts and modified routers: configure to use longer prefixes and shorter IIDs if desired. * Modified routers and mixture of modified and unmodified hosts on a link: Modified: - The modified hosts will use a shorter IID and longer prefix if that is announced. * The unmodified hosts, according to RFC 4861, MUST ignore the Reserved1 field. So, according to section 5.5.3 clause d) of RFC 4862, they will ignore any PIO advertising a shorter IID. Therefore, the operator has two choices: Unmodified: - 1. Decide that unmodified hosts will not be supported (i.e. will not be able to configure an address using SLAAC). - 2. Announce (at least) two prefixes on the link - a /64 and a longer one, with a shorter IID. For that to make sense, we need an extra rule for modified hosts: if a host receives several PIOs from the same router, it prefers all those with the shortest IID and ignores the others. Mixure of Modifiled and Unmodified hosts router on a link is not recommmended. 5. Security Considerations The administrator should be aware to maintain 64 bit interface identifier for privacy when connected directly to the internet so that entropy for optimal heuristics are maintained for security. Variable length interface identifier shorter than 64 bits should be used within networks where there there are out-of-band guarantees that the hosts are trusted (e.g. corporate intranets and private networks). 6. IANA Considerations IANA Request for RA PIO registry for RESERVE2 Mishra, et al. Expires 9 January 2025 [Page 4] Internet-Draft Variable IID July 2024 7. Contributors Brian Carpenter. 8. Acknowledgements 9. References 9.1. Normative References [I-D.bourbaki-6man-classless-ipv6] Bourbaki, N., "IPv6 is Classless", Work in Progress, Internet-Draft, draft-bourbaki-6man-classless-ipv6-10, 1 April 2024, . [I-D.ietf-6lo-6lobac] Lynn, K., Martocci, J., Neilson, C., and S. Donaldson, "Transmission of IPv6 over Master-Slave/Token-Passing (MS/ TP) Networks", Work in Progress, Internet-Draft, draft- ietf-6lo-6lobac-08, 13 March 2017, . [I-D.ietf-6lowpan-btle] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., Shelby, Z., and C. Gomez, "Transmission of IPv6 Packets over BLUETOOTH Low Energy", Work in Progress, Internet- Draft, draft-ietf-6lowpan-btle-12, 12 February 2013, . [I-D.mishra-v6ops-variable-slaac-problem-stmt] Mishra, G. S., Petrescu, A., Kottapalli, N., Mudric, D., and D. Shytyi, "SLAAC with prefixes of arbitrary length in PIO (Variable SLAAC) - A Problem Statement", Work in Progress, Internet-Draft, draft-mishra-v6ops-variable- slaac-problem-stmt-06, 20 May 2023, . [I-D.templin-aerolink] Templin, F., "Asymmetric Extended Route Optimization (AERO)", Work in Progress, Internet-Draft, draft-templin- aerolink-82, 10 May 2018, . Mishra, et al. Expires 9 January 2025 [Page 5] Internet-Draft Variable IID July 2024 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2450] Hinden, R., "Proposed TLA and NLA Assignment Rule", RFC 2450, DOI 10.17487/RFC2450, December 1998, . [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, . [RFC2467] Crawford, M., "Transmission of IPv6 Packets over FDDI Networks", RFC 2467, DOI 10.17487/RFC2467, December 1998, . [RFC2470] Crawford, M., Narten, T., and S. Thomas, "Transmission of IPv6 Packets over Token Ring Networks", RFC 2470, DOI 10.17487/RFC2470, December 1998, . [RFC2492] Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999, . [RFC2497] Souvatzis, I., "Transmission of IPv6 Packets over ARCnet Networks", RFC 2497, DOI 10.17487/RFC2497, January 1999, . [RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast Addresses", RFC 2526, DOI 10.17487/RFC2526, March 1999, . [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels", RFC 2529, DOI 10.17487/RFC2529, March 1999, . [RFC2590] Conta, A., Malis, A., and M. Mueller, "Transmission of IPv6 Packets over Frame Relay Networks Specification", RFC 2590, DOI 10.17487/RFC2590, May 1999, . [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, DOI 10.17487/RFC2710, October 1999, . Mishra, et al. Expires 9 January 2025 [Page 6] Internet-Draft Variable IID July 2024 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 2001, . [RFC3146] Fujisawa, K. and A. Onoe, "Transmission of IPv6 Packets over IEEE 1394 Networks", RFC 3146, DOI 10.17487/RFC3146, October 2001, . [RFC3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address Allocations to Sites", RFC 3177, DOI 10.17487/RFC3177, September 2001, . [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses", RFC 3306, DOI 10.17487/RFC3306, August 2002, . [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, . [RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 3513, DOI 10.17487/RFC3513, April 2003, . [RFC3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global Unicast Address Format", RFC 3587, DOI 10.17487/RFC3587, August 2003, . [RFC3590] Haberman, B., "Source Address Selection for the Multicast Listener Discovery (MLD) Protocol", RFC 3590, DOI 10.17487/RFC3590, September 2003, . [RFC3627] Savola, P., "Use of /127 Prefix Length Between Routers Considered Harmful", RFC 3627, DOI 10.17487/RFC3627, September 2003, . [RFC3756] Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6 Neighbor Discovery (ND) Trust Models and Threats", RFC 3756, DOI 10.17487/RFC3756, May 2004, . [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, DOI 10.17487/RFC3775, June 2004, . Mishra, et al. Expires 9 January 2025 [Page 7] Internet-Draft Variable IID July 2024 [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, DOI 10.17487/RFC3810, June 2004, . [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address", RFC 3956, DOI 10.17487/RFC3956, November 2004, . [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, DOI 10.17487/RFC3972, March 2005, . [RFC4039] Park, S., Kim, P., and B. Volz, "Rapid Commit Option for the Dynamic Host Configuration Protocol version 4 (DHCPv4)", RFC 4039, DOI 10.17487/RFC4039, March 2005, . [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005, . [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, . [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for IPv6 Hosts and Routers", RFC 4213, DOI 10.17487/RFC4213, October 2005, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC4338] DeSanti, C., Carlson, C., and R. Nixon, "Transmission of IPv6, IPv4, and Address Resolution Protocol (ARP) Packets over Fibre Channel", RFC 4338, DOI 10.17487/RFC4338, January 2006, . [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)", RFC 4380, DOI 10.17487/RFC4380, February 2006, . Mishra, et al. Expires 9 January 2025 [Page 8] Internet-Draft Variable IID July 2024 [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006, . [RFC4548] Gray, E., Rutemiller, J., and G. Swallow, "Internet Code Point (ICP) Assignments for NSAP Addresses", RFC 4548, DOI 10.17487/RFC4548, May 2006, . [RFC4692] Huston, G., "Considerations on the IPv6 Host Density Metric", RFC 4692, DOI 10.17487/RFC4692, October 2006, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . [RFC4887] Thubert, P., Wakikawa, R., and V. Devarapalli, "Network Mobility Home Network Models", RFC 4887, DOI 10.17487/RFC4887, July 2007, . [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, . [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, . [RFC5072] Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6 over PPP", RFC 5072, DOI 10.17487/RFC5072, September 2007, . [RFC5121] Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S. Madanapalli, "Transmission of IPv6 via the IPv6 Convergence Sublayer over IEEE 802.16 Networks", RFC 5121, DOI 10.17487/RFC5121, February 2008, . Mishra, et al. Expires 9 January 2025 [Page 9] Internet-Draft Variable IID July 2024 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, DOI 10.17487/RFC5214, March 2008, . [RFC5375] Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O., and C. Hahn, "IPv6 Unicast Address Assignment Considerations", RFC 5375, DOI 10.17487/RFC5375, December 2008, . [RFC5453] Krishnan, S., "Reserved IPv6 Interface Identifiers", RFC 5453, DOI 10.17487/RFC5453, February 2009, . [RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming Shim Protocol for IPv6", RFC 5533, DOI 10.17487/RFC5533, June 2009, . [RFC5535] Bagnulo, M., "Hash-Based Addresses (HBA)", RFC 5535, DOI 10.17487/RFC5535, June 2009, . [RFC5692] Jeon, H., Jeong, S., and M. Riegel, "Transmission of IP over Ethernet over IEEE 802.16 Networks", RFC 5692, DOI 10.17487/RFC5692, October 2009, . [RFC5942] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet Model: The Relationship between Links and Subnet Prefixes", RFC 5942, DOI 10.17487/RFC5942, July 2010, . [RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) -- Protocol Specification", RFC 5969, DOI 10.17487/RFC5969, August 2010, . [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, DOI 10.17487/RFC6052, October 2010, . [RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126, DOI 10.17487/RFC6126, April 2011, . Mishra, et al. Expires 9 January 2025 [Page 10] Internet-Draft Variable IID July 2024 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, April 2011, . [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, . [RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address Assignment to End Sites", BCP 157, RFC 6177, DOI 10.17487/RFC6177, March 2011, . [RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011, . [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/RFC6437, November 2011, . [RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational Neighbor Discovery Problems", RFC 6583, DOI 10.17487/RFC6583, March 2012, . [RFC6741] Atkinson, RJ. and SN. Bhatti, "Identifier-Locator Network Protocol (ILNP) Engineering Considerations", RFC 6741, DOI 10.17487/RFC6741, November 2012, . [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: Combination of Stateful and Stateless Translation", RFC 6877, DOI 10.17487/RFC6877, April 2013, . [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic Requirements for IPv6 Customer Edge Routers", RFC 7084, DOI 10.17487/RFC7084, November 2013, . [RFC7094] McPherson, D., Oran, D., Thaler, D., and E. Osterweil, "Architectural Considerations of IP Anycast", RFC 7094, DOI 10.17487/RFC7094, January 2014, . Mishra, et al. Expires 9 January 2025 [Page 11] Internet-Draft Variable IID July 2024 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque Interface Identifiers with IPv6 Stateless Address Autoconfiguration (SLAAC)", RFC 7217, DOI 10.17487/RFC7217, April 2014, . [RFC7278] Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6 /64 Prefix from a Third Generation Partnership Project (3GPP) Mobile Interface to a LAN Link", RFC 7278, DOI 10.17487/RFC7278, June 2014, . [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, . [RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, DOI 10.17487/RFC7368, October 2014, . [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit Boundary in IPv6 Addressing", RFC 7421, DOI 10.17487/RFC7421, January 2015, . [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 2016, . [RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu, "Recommendation on Stable IPv6 Interface Identifiers", RFC 8064, DOI 10.17487/RFC8064, February 2017, . [RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017, . [RFC8156] Mrugalski, T. and K. Kinnear, "DHCPv6 Failover Protocol", RFC 8156, DOI 10.17487/RFC8156, June 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Mishra, et al. Expires 9 January 2025 [Page 12] Internet-Draft Variable IID July 2024 [RFC8425] Troan, O., "IANA Considerations for IPv6 Neighbor Discovery Prefix Information Option Flags", RFC 8425, DOI 10.17487/RFC8425, July 2018, . 9.2. Informative References [RFC8273] Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix per Host", RFC 8273, DOI 10.17487/RFC8273, December 2017, . Authors' Addresses Gyan Mishra Verizon Inc. Email: gyan.s.mishra@verizon.com Dmytro Shytyi 6WIND Paris France Email: dmytro@shytyi.net Alexandre Petrescu CEA, LIST CEA Saclay 91190 Gif-sur-Yvette France Phone: +33169089223 Email: Alexandre.Petrescu@cea.fr Naveen Kottapalli Ciena 300 Concord Road Billerica, MA 01821 United States of America Phone: +1 978 223 4700 Email: nkottapalli@benu.net Dusan Mudric Ciena Canada Phone: +1-613-670-2425 Email: dmudric@ciena.com Mishra, et al. Expires 9 January 2025 [Page 13]