IPv6 Maintenance J. Linkova Internet-Draft Google Updates: 4861 (if approved) 29 February 2024 Intended status: Standards Track Expires: 1 September 2024 Triggering Unsolicited Router Advertisements Upon Configuration Changes draft-link-6man-truce-00 Abstract IPv6 routers employ Router Advertisements (RAs) to disseminate essential network configuration data to hosts. RAs play a vital role in Stateless address autoconfiguration (SLAAC) and providing IPv6 connectivity. Timely updates via RAs become paramount as network configurations change to prevent service outages. This document modifies RFC4861, recommending immediate propagation of configuration information changes by routers. 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 1 September 2024. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Linkova Expires 1 September 2024 [Page 1] Internet-Draft Triggering Router Advertisements Upon Ch February 2024 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. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 3. Changes to RFC4861 . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Router Advertisements (RAs) contain information that IPv6 hosts use to configure their networks and establish connectivity. Examples of such information include but are not limited to: * Prefix Information Options ([RFC4861]): Advertise network prefixes, allowing hosts to automatically configure IPv6 addresses (SLAAC). * Link MTU ([RFC4861]): Informs hosts about the maximum packet size supported on the link, preventing fragmentation. * DNS Recursive Server Addresses ([RFC8106]): Provides DNS servers for domain name resolution. * NAT64 Prefix ([RFC8781]): Indicates the presence of a NAT64 translator, enabling communication between IPv6 and IPv4 networks. Network configurations can change over time, and these changes must be communicated to hosts. Routers propagate updates either by sending unsolicited RAs or by responding with an RA to a host's Router Solicitation (RS) message. While some changes (like adding a new prefix or DNS server) can be safely included in the next scheduled RA, others require immediate action to prevent service Linkova Expires 1 September 2024 [Page 2] Internet-Draft Triggering Router Advertisements Upon Ch February 2024 disruptions. In particular, the removal of a prefix, DNS server, or NAT64 service necessitates a timely update to ensure hosts discontinue using outdated and non-functional resources. A frequent issue arises during network renumbering, when the prefix used for SLAAC and/or on-link communication is modified. If the router fails to send an immediate unsolicited RA upon a prefix change, hosts might continue selecting source addresses from the outdated prefix for up to MaxRtrAdvInterval (65535 seconds, [RFC8319]). Communications using those addresses will fail since the old prefix is no longer valid. Residential networks, where prefixes are often delegated to Customer Edge (CE) routers via DHCPv6-PD, are particularly susceptible to this issue. To ensure timely prefix change notifications, Requirement L-13 of [RFC7084] states: If the delegated prefix changes, i.e., the current prefix is replaced with a new prefix without any overlapping time period, then the IPv6 CE router MUST immediately advertise the old prefix with a Preferred Lifetime of zero and a Valid Lifetime of either a) zero or b) the lower of the current Valid Lifetime and two hours (which must be decremented in real time) in a Router Advertisement message as described in Section 5.5.3, (e) of [RFC4862]. It's important to note that this requirement applies specifically to CE routers and addresses prefix changes only. Section 6.2.4 of [RFC4861] says: The information contained in Router Advertisements may change through actions of system management. For instance, the lifetime of advertised prefixes may change, new prefixes could be added, a router could cease to be a router (i.e., switch from being a router to being a host), etc. In such cases, the router MAY transmit up to MAX_INITIAL_RTR_ADVERTISEMENTS unsolicited advertisements, using the same rules as when an interface becomes an advertising interface. Consequently, routers not classified as CE equipment and therefore exempt from [RFC7084] are not required to immediately notify hosts about network configuration changes. This can lead to degraded user experience and contribute to a negative perception of IPv6 reliability. Linkova Expires 1 September 2024 [Page 3] Internet-Draft Triggering Router Advertisements Upon Ch February 2024 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. Changes to RFC4861 This document makes the following changes to Section 6.2.4 of [RFC4861], OLD TEXT: === The information contained in Router Advertisements may change through actions of system management. For instance, the lifetime of advertised prefixes may change, new prefixes could be added, a router could cease to be a router (i.e., switch from being a router to being a host), etc. In such cases, the router MAY transmit up to MAX_INITIAL_RTR_ADVERTISEMENTS unsolicited advertisements, using the same rules as when an interface becomes an advertising interface. === NEW TEXT === The information contained in Router Advertisements may change through actions of system management. For instance, the lifetime of advertised prefixes may change, new prefixes could be added, a router could cease to be a router (i.e., switch from being a router to being a host), etc. In such cases, the router SHOULD transmit up to MAX_INITIAL_RTR_ADVERTISEMENTS unsolicited advertisements, using the same rules as when an interface becomes an advertising interface. === 4. Security Considerations This document does not introduce any security considerations. 5. Privacy Considerations Linkova Expires 1 September 2024 [Page 4] Internet-Draft Triggering Router Advertisements Upon Ch February 2024 6. IANA Considerations This memo does not introduce any IANA considerations. 7. References 7.1. 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, . [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, . [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, . 7.2. Informative References [RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 8106, DOI 10.17487/RFC8106, March 2017, . [RFC8319] Krishnan, S., Korhonen, J., Chakrabarti, S., Nordmark, E., and A. Yourtchenko, "Support for Adjustable Maximum Router Lifetimes per Link", RFC 8319, DOI 10.17487/RFC8319, February 2018, . [RFC8781] Colitti, L. and J. Linkova, "Discovering PREF64 in Router Advertisements", RFC 8781, DOI 10.17487/RFC8781, April 2020, . Acknowledgements Thanks to Erik Kline for the discussions, the input and all contribution. Linkova Expires 1 September 2024 [Page 5] Internet-Draft Triggering Router Advertisements Upon Ch February 2024 Author's Address Jen Linkova Google 1 Darling Island Rd Pyrmont NSW 2009 Australia Email: furry13@gmail.com, furry@google.com Linkova Expires 1 September 2024 [Page 6]