6man R. Bonica Internet-Draft Juniper Networks Obsoletes: RFC 2711 (if approved) 8 November 2024 Intended status: Standards Track Expires: 12 May 2025 Deprecation Of The IPv6 Router Alert Option draft-ietf-6man-deprecate-router-alert-03 Abstract This document deprecates the IPv6 Router Alert Option. Protocols that use the Router Alert Option may continue to do so, even in future versions. However, protocols that are standardized in the future must not use the Router Alert Option. This document obsoletes RFC 2711. 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 12 May 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Bonica Expires 12 May 2025 [Page 1] Internet-Draft Deprecate IPv6 Router Alert November 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. Alternatives To The Router Alert Option . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5 Appendix A. Protocols That Use The Router Alert Option . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction In IPv6 [RFC8200], optional internet-layer information is encoded in separate headers that may be placed between the IPv6 header and the upper-layer header in a packet. There is a small number of such extension headers, each one identified by a distinct Next Header value. One of these extension headers is called the Hop-by-Hop Options header. The Hop-by-Hop Options header is used to carry optional information that may be examined and processed by every node along a packet's delivery path. The Hop-by-Hop Options header can carry one or more options. Among these is the Router Alert Option [RFC2711]. The Router Alert Option provides a mechanism whereby routers can know when to intercept datagrams not addressed to them without having to extensively examine every datagram. The semantic of the Router Alert Option is, "routers should examine this datagram more closely". Not including this option tells the router that there is no need to closely examine the contents of the datagram. Bonica Expires 12 May 2025 [Page 2] Internet-Draft Deprecate IPv6 Router Alert November 2024 [RFC6398] identifies security considerations associated with the Router Alert Option. In a nutshell, the IP Router Alert Option does not provide a universal mechanism to accurately and reliably distinguish between IP Router Alert packets of interest and unwanted IP Router Alerts. This creates a security concern, because, short of appropriate router-implementation-specific mechanisms, the router's control plane is at risk of being flooded by unwanted traffic. NOTE: Many routers maintain separation between forwarding and control plane hardware. The forwarding plain is implemented on high- performance Application Specific Integrated Circuits (ASIC) and Network Processors (NP), while the control plane is implemented on general-purpose processors. Given this difference, the control plane is more susceptible to a Denial-of-Service (DoS) attack than the forwarding plane. [RFC6192] demonstrates how a network operator can deploy Access Control Lists (ACL) that protect the control plane from DoS attack. These ACLs are effective and efficient when they select packets based upon information that can be found in a fixed position. However, they become less effective and less efficient when they must parse an IPv6 Hop-by-hop Options header, searching for the Router Alert Option. So, network operators can address the security considerations raised in RFC 6398 by: * Deploying the operationally complex and computationally expensive ACLs described in RFC 6192. * Configuring their routers to ignore the Router Alert Option. * Dropping or severely rate limiting packets that contain the IPv6 Hop-by-hop Options header at the network edge. These options become less viable as protocol designers continue to design protocols that use the Router Alert Option. [RFC9673] seeks to eliminate Hop-by-Hop processing on the control plane. However, because of its unique function, the Router Alert option is granted an exception to this rule. One approach would be to deprecate the Router Alert option, because current usage beyond the local network appears to be limited, and packets containing Hop- by-Hop options are frequently dropped. Deprecation would allow current implementations to continue using it, but its use could be phased out over time. Bonica Expires 12 May 2025 [Page 3] Internet-Draft Deprecate IPv6 Router Alert November 2024 Therefore, this document deprecates the IPv6 Router Alert Option. Protocols that use the Router Alert Option MAY continue to do so, even in future versions. However, protocols that are standardized in the future MUST NOT use the Router Alert Option. Appendix A contains a list of protocols that may continue to use the Router Alert Option. This document obsoletes RFC 2711. 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. Alternatives To The Router Alert Option The following is an alternative to the Router Alert Option for unicast traffic being sent from a source node to an ultimate destination node along a delivery path: * The source node encodes the ultimate destination node's address in the message body. * The source node sets packet's destination address to that of the next node along the delivery path. * The source node sends the packet to the next node along the delivery path. * The next node along the delivery path processes the packet and repeats the process. The following is an alternative to the Router Address Option for multicast traffic being sent from a source node to all nodes on the directly connected subnetwork: * The source node encodes the target multicast address in the message body. * The source node sends the packet to a well-known multicast address (e.g., All-PROTOCOL-X-ROUTERS). 4. Security Considerations This document extends the security considerations provided in RFC 2711, RFC 6192 and RFC 6398. Bonica Expires 12 May 2025 [Page 4] Internet-Draft Deprecate IPv6 Router Alert November 2024 5. IANA Considerations IANA is requested to mark the Router Alert Option as Deprecated in the Destination Options and Hop-by-hop Options Registry ( https://www.iana.org/assignments/ipv6-parameters/ ipv6-parameters.xhtml#ipv6-parameters-2) and add a pointer to this document. 6. Acknowledgements Thanks to Zafar Ali, Brian Carpenter, Toerless Eckert, David Farmer, Adrian Farrel, and Bob Hinden for their reviews of this document. 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, . [RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option", RFC 2711, DOI 10.17487/RFC2711, October 1999, . [RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [RFC9673] Hinden, R. and G. Fairhurst, "IPv6 Hop-by-Hop Options Processing Procedures", RFC 9673, DOI 10.17487/RFC9673, October 2024, . 7.2. Informative References Bonica Expires 12 May 2025 [Page 5] Internet-Draft Deprecate IPv6 Router Alert November 2024 [RFC1633] Braden, R., Clark, D., and S. Shenker, "Integrated Services in the Internet Architecture: an Overview", RFC 1633, DOI 10.17487/RFC1633, June 1994, . [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001, . [RFC3175] Baker, F., Iturralde, C., Le Faucheur, F., and B. Davie, "Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC 3175, DOI 10.17487/RFC3175, September 2001, . [RFC3208] Speakman, T., Crowcroft, J., Gemmell, J., Farinacci, D., Lin, S., Leshchiner, D., Luby, M., Montgomery, T., Rizzo, L., Tweedly, A., Bhaskar, N., Edmonstone, R., Sumanasekera, R., and L. Vicisano, "PGM Reliable Transport Protocol Specification", RFC 3208, DOI 10.17487/RFC3208, December 2001, . [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, DOI 10.17487/RFC3810, June 2004, . [RFC4080] Hancock, R., Karagiannis, G., Loughney, J., and S. Van den Bosch, "Next Steps in Signaling (NSIS): Framework", RFC 4080, DOI 10.17487/RFC4080, June 2005, . [RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery", RFC 4286, DOI 10.17487/RFC4286, December 2005, . [RFC5946] Le Faucheur, F., Manner, J., Narayanan, A., Guillou, A., and H. Malik, "Resource Reservation Protocol (RSVP) Extensions for Path-Triggered RSVP Receiver Proxy", RFC 5946, DOI 10.17487/RFC5946, October 2010, . [RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet Signalling Transport", RFC 5971, DOI 10.17487/RFC5971, October 2010, . Bonica Expires 12 May 2025 [Page 6] Internet-Draft Deprecate IPv6 Router Alert November 2024 [RFC5979] Shen, C., Schulzrinne, H., Lee, S., and J. Bang, "NSIS Operation over IP Tunnels", RFC 5979, DOI 10.17487/RFC5979, March 2011, . [RFC6016] Davie, B., Le Faucheur, F., and A. Narayanan, "Support for the Resource Reservation Protocol (RSVP) in Layer 3 VPNs", RFC 6016, DOI 10.17487/RFC6016, October 2010, . [RFC6192] Dugal, D., Pignataro, C., and R. Dunn, "Protecting the Router Control Plane", RFC 6192, DOI 10.17487/RFC6192, March 2011, . [RFC6401] Le Faucheur, F., Polk, J., and K. Carlberg, "RSVP Extensions for Admission Priority", RFC 6401, DOI 10.17487/RFC6401, October 2011, . [RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert Option for MPLS Operations, Administration, and Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April 2015, . [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., Aldrin, S., and M. Chen, "Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures", RFC 8029, DOI 10.17487/RFC8029, March 2017, . [RFC9570] Kompella, K., Bonica, R., and G. Mirsky, Ed., "Deprecating the Use of Router Alert in LSP Ping", RFC 9570, DOI 10.17487/RFC9570, May 2024, . Appendix A. Protocols That Use The Router Alert Option Table 1 contains a list of protocols that use the IPv6 Router Alert Option. There are no known IPv6 implementations of MPLS PING. Neither INTSERV nor NSIS are widely deployed. All NSIS protocols are EXPERIMENTAL. Pragmatic Generic Multicast (PGM) is EXPERIMENTAL and there are no known IPv6 implementations. Bonica Expires 12 May 2025 [Page 7] Internet-Draft Deprecate IPv6 Router Alert November 2024 +=================+=============================+==================+ | Protocol | References | Application | +=================+=============================+==================+ | Multicast | [RFC3810] | IPv6 Multicast | | Listener | | | | Discovery | | | | Version 2 | | | | (MLDv2) | | | +-----------------+-----------------------------+------------------+ +-----------------+-----------------------------+------------------+ | Multicast | [RFC4286] | IPv6 Multicast | | Router | | | | Discovery (MRD) | | | +-----------------+-----------------------------+------------------+ +-----------------+-----------------------------+------------------+ | Pragmatic | [RFC3208] | IPv6 Multicast | | General | | | | Multicast (PGM) | | | +-----------------+-----------------------------+------------------+ +-----------------+-----------------------------+------------------+ | MPLS PING (Use | [RFC7506][RFC8029][RFC9570] | MPLS OAM | | of router alert | | | | deprecated) | | | +-----------------+-----------------------------+------------------+ +-----------------+-----------------------------+------------------+ | Resource | [RFC3175] [RFC5946] | Integrated | | Reservation | [RFC6016] [RFC6401] | Services | | Protocol | | (INTSERV) | | (RSVP): Both | | [RFC1633] and | | IPv4 and IPv6 | | Multiprotocol | | implementations | | Label Switching | | | | (MPLS) [RFC3031] | +-----------------+-----------------------------+------------------+ +-----------------+-----------------------------+------------------+ | Next Steps In | [RFC5979] [RFC5971] | NSIS [RFC4080] | | Signaling | | | | (NSIS) | | | +-----------------+-----------------------------+------------------+ Table 1: Protocols That Use The IPv6 Router Alert Option Author's Address Ron Bonica Juniper Networks United States of America Email: rbonica@juniper.net Bonica Expires 12 May 2025 [Page 8]