Internet Engineering Task Force (IETF) R. Bonica
Request for Comments: 9805 Juniper Networks
Updates: 2711 June 2025
Category: Standards Track
ISSN: 2070-1721
Deprecation of the IPv6 Router Alert Option for New Protocols
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 is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9805.
Copyright Notice
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Table of Contents
1. Introduction
2. Requirements Language
3. Issues Associated with the IPv6 Router Alert Option
4. Deprecation of the IPv6 Router Alert Option
5. Future Work
6. Security Considerations
7. IANA Considerations
8. References
8.1. Normative References
8.2. Informative References
Appendix A. Protocols That Use the Router Alert Option
Acknowledgements
Author's Address
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 that "routers should examine this datagram more closely".
Excluding this option tells the router that there is no need to
examine this datagram more closely.
As explained below, the Router Alert Option introduces many issues.
This document updates [RFC2711]. Implementers of protocols that
continue to use the Router Alert 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
| high-performance Application-Specific Integrated Circuits
| (ASICs) and Network Processors (NPs), while the control plane
| is implemented on general-purpose processors. Given this
| difference, the control plane is more susceptible to a Denial-of-Service Denial-
| of-Service (DoS) attack than the forwarding plane.
[RFC6192] demonstrates how a network operator can deploy Access
Control Lists (ACLs) that protect the control plane from DoS attacks.
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 a
Hop-by-Hop Options header, searching for the Router Alert Option.
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.
* Dropping or severely rate limiting packets that contain the IPv6
Hop-by-Hop 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. Deprecation of 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 MAY continue to use the Router
Alert Option.
This document updates [RFC2711].
5. Future Work
A number of protocols use the Router Alert option; these are listed
in Appendix A. The only protocols in Appendix A that have widespread
deployment are Multicast Listener Discovery Version 2 (MLDv2)
[RFC3810]
[RFC9777] and Multicast Router Discovery (MRD) [RFC4286]. The other
protocols either have 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].
7. IANA Considerations
IANA has marked 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> and added
this document as a reference.
IANA has also made a note in the "IPv6 Router Alert Option Values"
registry <https://www.iana.org/assignments/ipv6-routeralert-values>
stating that the registry is closed for allocations and added a
reference to this document. The experimental codepoints in this
registry have been changed to "Reserved" (i.e., they are no longer
available for experimentation).
8. References
8.1. 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>.
[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>.
8.2. 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>.
[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>.
[RFC9777] Haberman, B., Ed., "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", STD 101, RFC 9777,
DOI 10.17487/RFC9777, March 2025,
<https://www.rfc-editor.org/info/rfc9777>.
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 Integrated Services (INTSERV) (Intserv) nor Next Steps in
Signaling (NSIS) are widely deployed. All NSIS protocols are
experimental. Pragmatic Generic Multicast (PGM) is experimental, and
there are no known IPv6 implementations.
+=================+=============================+==================+
| Protocol | References | Application |
+=================+=============================+==================+
| Multicast | [RFC3810] [RFC9777] | 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 Operations, |
| of router alert the Router | | Administration, |
| deprecated) Alert Option is | | and Maintenance |
| deprecated) | | (OAM) |
+-----------------+-----------------------------+------------------+
| Resource | [RFC3175] [RFC5946] | Integrated |
| Reservation | [RFC6016] [RFC6401] | Services |
| Protocol | | (INTSERV) (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
Acknowledgements
Thanks to Zafar Ali, Brian Carpenter, Toerless Eckert, David Farmer,
Adrian Farrel, Bob Hinden, and Jen Linkova for their reviews of this
document.
Author's Address
Ron Bonica
Juniper Networks
United States of America
Email: rbonica@juniper.net