Internet DRAFT - draft-link-6man-truce
draft-link-6man-truce
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.
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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.
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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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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
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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.
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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
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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,
<https://www.rfc-editor.org/info/rfc2119>.
[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,
<https://www.rfc-editor.org/info/rfc4861>.
[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,
<https://www.rfc-editor.org/info/rfc7084>.
[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>.
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,
<https://www.rfc-editor.org/info/rfc8106>.
[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, <https://www.rfc-editor.org/info/rfc8319>.
[RFC8781] Colitti, L. and J. Linkova, "Discovering PREF64 in Router
Advertisements", RFC 8781, DOI 10.17487/RFC8781, April
2020, <https://www.rfc-editor.org/info/rfc8781>.
Acknowledgements
Thanks to Erik Kline for the discussions, the input and all
contribution.
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Author's Address
Jen Linkova
Google
1 Darling Island Rd
Pyrmont NSW 2009
Australia
Email: furry13@gmail.com, furry@google.com
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