Internet Engineering Task Force T. Winters Internet-Draft QA Cafe Updates: 7084 (if approved) 21 April 2025 Intended status: Informational Expires: 23 October 2025 IPv6 CE Routers LAN Prefix Delegation draft-ietf-v6ops-cpe-lan-pd-07 Abstract This document defines requirements for IPv6 Customer Edge (CE) routers to support DHCPv6 Prefix Delegation for distributing unused prefixes that were delegated to a IPv6 CE router. This document updates RFC 7084. 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 23 October 2025. Copyright Notice Copyright (c) 2025 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. Winters Expires 23 October 2025 [Page 1] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. IPv6 End-User Network Architecture . . . . . . . . . . . . . 3 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. LAN Prefix Delegation Requirements (LPD) . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction This document defines requirements for DHCPv6 Prefix Delegation in IPv6 Customer Edge (CE) routers ([RFC7084]) in order to properly utilize the IPv6 prefixes assigned by service providers. Many service providers assign larger address blocks than /64 to CE routers, as recommended in [RFC6177]. If an IPv6 CE router does not support the Identity Association for Prefix Delegation (IA_PD) Prefix Option (Section 21.21 of [RFC8415]) on the LAN, it will not be able to assign any prefixes beyond its local interfaces, limiting the usefulness of assigning prefixes larger than /64 by the operator. Supporting IA_PD on the LAN interfaces of a CE Router will allow those unused prefixes to be distributed into a network. Note that efforts such as Stub Networking Auto Configuration (SNAC) Working Group that depends on IPv6 prefixes being properly distributed in the LAN. Two models, hierarchical prefix and flat, were proposed in the past for prefix sub-delegation beyond an IPv6 CE router. Hierarchical prefix delegation requires an IPv6 CE router to sub delegate IPv6 prefixes based on set of rules. If more than one router uses hierarchical prefix delegation, an IPv6 prefix tree is created. When no routing protocol is enabled to discover the network topology, it is possible to have unbalanced prefix delegation tree which leads to running out of prefixes. More information on heirarchical prefix delegation can be found, e.g., in Section 8.5 of CableLabs IPv6 eRouter Specifiction [eRouter]. A flat prefix delegation requires the router to be provisioned with the initial prefix and to assign /64 prefixes to all other prefix requests from routers in the LAN- facing interface. The default configuration of CE Router supporting prefix delegation is designed to be a flat model to support zero configuration networking. Winters Expires 23 October 2025 [Page 2] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 This document does not cover dealing with multi-provisioned networks with more than one provider. Due to complexity of a solution that would require routing, provisioning and policy, this is out of scope of this document. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Terminology The following terminology is defined for this document. * IPv6 node: a device that implements IPv6 * IPv6 router: a node that forwards IPv6 packets not explicitly addressed to itself. * IPv6 host: Any IPv6 node that is not a router. * ULA:Unique Local Address as defined in [RFC4193]. * GUA:Global Unique Addresses as defined in [RFC4291]. 4. IPv6 End-User Network Architecture The end-user network for IPv6 that is a stub network. Figure 1 illustrates the model topology. Winters Expires 23 October 2025 [Page 3] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 +-----------+ | Service | | Provider | | Router | +-----+-----+ | | | Customer | Internet Connection | +-----v-----+ | IPv6 | | CE | | Router | +-----+-----+ | +------+-------+ | | | | +---+----+ +-----+------+ | IPv6 | | | | Host | | Router | | | | | +--------+ +------------+ Figure 1: Example IPv6 End User Topology 5. Requirements IPv6 CE router distribute configuration information obtained during WAN interface provisioning to LAN-facing IPv6 hosts and routers. An [RFC7084] compliant CE router would only provide IPv6 hosts with configuration information. This allows for addressing and routing of IPv6 prefixes to both hosts and routers. These requirements are in addition to the ones in Section 4.3 of [RFC7084]. 5.1. LAN Prefix Delegation Requirements (LPD) LPD-1: IPv6 CE routers MUST support IPv6 prefix assignment according to [RFC8415] (Identity Association for Prefix Delegation (IA_PD) option) on its LAN interface. LPD-2: IPv6 CE routers MUST assign a prefix from the delegated prefix as specified by L-2 in Section 4.3 of [RFC7084]. If insufficient prefixes are available the IPv6 CE Router SHOULD log a system management error. Winters Expires 23 October 2025 [Page 4] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 LPD-3: The prefix assigned to a link MUST NOT change in the absence of a local policy or a topology change. LPD-4: After LAN link prefix assignments, the IPv6 CE router MUST make the remaining IPv6 prefixes available to other routers via Prefix Delegation. LPD-5: IPv6 CE routers MUST maintain a local routing table that is dynamically updated with leases and the associated next hops as they are delegated to clients. When a delegated prefix is released or expires, the associated route MUST be removed from the IPv6 CE router's routing table. LPD-6: By default, the IPv6 CE router filtering rules MUST allow forwarding of packets with an outer IPv6 header containing a source address belonging to Delegated Prefixes, along with reciprocal packets from the same flow, following the recommendations of [RFC6092]. This updates WPD-5 of [RFC7084] to not drop packets from prefixes that have been delegated. IPv6 CE routers MUST continue to drop packets destination address that is not assigned to the LAN or delegated. LPD-7: The IPv6 CE routers MUST provision IA_PD prefixes with a prefix-length of 64 on the LAN-facing interface unless configured to use a different prefix-length or the CE Router administrator. The prefix length of 64 is used as that is the current prefix length supported by SLAAC. For hierarchical prefix delegation a prefix-length shorter then 64 may be configured. LPD-8: IPv6 CE routers configured to generate a ULA prefix as defined in ULA-1 of Section 4.3 of [RFC7084] MUST continue to provision available GUA IPv6 prefixes. LPD-9: If an IPv6 CE router is provisioning both ULA and GUA via prefix delegation, the GUA SHOULD appear first in the packet. LPD-10: IPv6 CE routers MUST NOT delegate prefixes via DHCPv6 on the LAN using lifetimes that exceed the remaining lifetimes of the corresponding prefixes learned on the WAN. 6. Security Considerations This document does not add any new security considerations beyond those mentioned in Section 4 of [RFC8213], Section 22 of [RFC8415] and [RFC6092]. Winters Expires 23 October 2025 [Page 5] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 7. IANA Considerations This document makes no request of IANA. 8. Acknowledgements Thanks to the following people for their guidance and feedback: Marion Dillon, Erik Auerswald, Esko Dijk, Tim Carlin, Richard Patterson, Ted Lemon, Michael Richardson, Martin Huneki, Gabor Lencse, Ole Troan, Brian Carpenter, David Farmer, Kyle Rose, Mohamed Boucadair, Tim Chown, Ron Bonica, and Erica Johnson. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet Service", RFC 6092, DOI 10.17487/RFC6092, January 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, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Winters Expires 23 October 2025 [Page 6] Internet-Draft IPv6 CE Routers LAN Prefix Delegation April 2025 [RFC8213] Volz, B. and Y. Pal, "Security of Messages Exchanged between Servers and Relay Agents", RFC 8213, DOI 10.17487/RFC8213, August 2017, . [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., Richardson, M., Jiang, S., Lemon, T., and T. Winters, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 8415, DOI 10.17487/RFC8415, November 2018, . 9.2. Informative References [eRouter] CableLabs, "IPv4 and IPv6 eRouter Specification Version I21", February 2022, . Author's Address Timothy Winters QA Cafe 100 Main Street, Suite #212 Dover, NH 03820 United States of America Email: tim@qacafe.com Winters Expires 23 October 2025 [Page 7]