Deprecation Of The IPv6 Router Alert Option For New Protocols
draft-ietf-6man-deprecate-router-alert-13

6man                                                           R. Bonica
Internet-Draft                                          Juniper Networks
Updates: 2711 (if approved)                                29 April 2025
Intended status: Standards Track                                        
Expires: 31 October 2025

     Deprecation Of The IPv6 Router Alert Option For New Protocols
               draft-ietf-6man-deprecate-router-alert-13

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, new protocols that are standardized in the
   future must not use the Router Alert Option.

   This document updates 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
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   This Internet-Draft will expire on 31 October 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Issues Associated With The IPv6 Router Alert Option . . . . .   3
   4.  Deprecate The IPv6 Router Alert Option  . . . . . . . . . . .   4
   5.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   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".
   Excluding this option tells the router that there is no need to
   examine this datagram more closely.

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   As explained below, the Router Alert Option introduces many issues.

   This document updates [RFC2711].

   Implementers of protocols that continue to use the Router Option can
   continue to reference [RFC2711] for Router Alert Option details.

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.  Issues Associated With The IPv6 Router Alert Option

   [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 plane 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 [RFC6398] by:

   *  Deploying the operationally complex and computationally expensive
      ACLs described in [RFC6192].

   *  Configuring their routers to ignore the Router Alert Option.

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   *  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.

4.  Deprecate The IPv6 Router Alert Option

   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, new protocols that are standardized in the
   future MUST NOT use the Router Alert Option.  Appendix A contains an
   exhaustive list of protocols that may continue to use the Router
   Alert Option.

   This document updates [RFC2711].

5.  Future Work

   As listed in Appendix A, there are a number of protocols that use the
   Router Alert option.  The only protocols in the Appendix that have
   wide spread deployment are Multicast Listener Discovery Version 2
   (MLDv2) [RFC3810] and Multicast Router Discovery (MRD) [RFC4286].
   The other protocols have either limited deployment, are Experimental,
   or have no known implementation.

   It is left for future work to develop new versions of MLDv2 and MRD
   that do not rely on the Router Alert option.  That task is out of
   scope for this document.

6.  Security Considerations

   This document mitigates all security considerations associated with
   the IPv6 Router Alert Option.  These security considerations can be
   found in [RFC2711], [RFC6192] and [RFC6398].

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7.  IANA Considerations

   IANA is requested to mark the Router Alert Option as "Deprecated for
   New Protocols" 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.

   IANA is also requested to make a note in the IPv6 Router Alert Option
   Values Registry (https://www.iana.org/assignments/ipv6-routeralert-
   values/ipv6-routeralert-values.xhtml?) stating that this registry is
   closed for allocations along with a reference to this document.
   Please change all experimental codepoints in this registry as
   "reserved" (i.e., they are no longer available for experimentation).

8.  Acknowledgements

   Thanks to Zafar Ali, Brian Carpenter, Toerless Eckert, David Farmer,
   Adrian Farrel, Bob Hinden and Jen Linkova for their reviews of this
   document.

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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2711]  Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
              RFC 2711, DOI 10.17487/RFC2711, October 1999,
              <https://www.rfc-editor.org/info/rfc2711>.

   [RFC6398]  Le Faucheur, F., Ed., "IP Router Alert Considerations and
              Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October
              2011, <https://www.rfc-editor.org/info/rfc6398>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

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   [RFC9673]  Hinden, R. and G. Fairhurst, "IPv6 Hop-by-Hop Options
              Processing Procedures", RFC 9673, DOI 10.17487/RFC9673,
              October 2024, <https://www.rfc-editor.org/info/rfc9673>.

9.2.  Informative References

   [RFC1633]  Braden, R., Clark, D., and S. Shenker, "Integrated
              Services in the Internet Architecture: an Overview",
              RFC 1633, DOI 10.17487/RFC1633, June 1994,
              <https://www.rfc-editor.org/info/rfc1633>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [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,
              <https://www.rfc-editor.org/info/rfc3175>.

   [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, <https://www.rfc-editor.org/info/rfc3208>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <https://www.rfc-editor.org/info/rfc3810>.

   [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,
              <https://www.rfc-editor.org/info/rfc4080>.

   [RFC4286]  Haberman, B. and J. Martin, "Multicast Router Discovery",
              RFC 4286, DOI 10.17487/RFC4286, December 2005,
              <https://www.rfc-editor.org/info/rfc4286>.

   [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,
              <https://www.rfc-editor.org/info/rfc5946>.

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   [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
              Signalling Transport", RFC 5971, DOI 10.17487/RFC5971,
              October 2010, <https://www.rfc-editor.org/info/rfc5971>.

   [RFC5979]  Shen, C., Schulzrinne, H., Lee, S., and J. Bang, "NSIS
              Operation over IP Tunnels", RFC 5979,
              DOI 10.17487/RFC5979, March 2011,
              <https://www.rfc-editor.org/info/rfc5979>.

   [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,
              <https://www.rfc-editor.org/info/rfc6016>.

   [RFC6192]  Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
              Router Control Plane", RFC 6192, DOI 10.17487/RFC6192,
              March 2011, <https://www.rfc-editor.org/info/rfc6192>.

   [RFC6401]  Le Faucheur, F., Polk, J., and K. Carlberg, "RSVP
              Extensions for Admission Priority", RFC 6401,
              DOI 10.17487/RFC6401, October 2011,
              <https://www.rfc-editor.org/info/rfc6401>.

   [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, <https://www.rfc-editor.org/info/rfc7506>.

   [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,
              <https://www.rfc-editor.org/info/rfc8029>.

   [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,
              <https://www.rfc-editor.org/info/rfc9570>.

Appendix A.  Protocols That Use The Router Alert Option

   Table 1 contains an exhaustive 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.

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   +=================+=============================+==================+
   | 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

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