Improving the Reaction of Customer Edge Routers to Renumbering Events
draft-ietf-v6ops-cpe-slaac-renum-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (v6ops WG) | |
|---|---|---|---|
| Authors | Fernando Gont , Jan Zorz , Richard Patterson | ||
| Last updated | 2020-03-09 (Latest revision 2020-02-19) | ||
| Replaces | draft-gont-v6ops-cpe-slaac-renum | ||
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draft-ietf-v6ops-cpe-slaac-renum-01
IPv6 Operations Working Group (v6ops) F. Gont
Internet-Draft SI6 Networks
Intended status: Informational J. Zorz
Expires: September 10, 2020 Go6 Institute
R. Patterson
Sky UK
March 9, 2020
Improving the Reaction of Customer Edge Routers to Renumbering Events
draft-ietf-v6ops-cpe-slaac-renum-01
Abstract
In scenarios where network configuration information related to IPv6
prefixes becomes invalid without any explicit signaling of that
condition (such as when a Customer Edge Router crashes and reboots
without knowledge of the previously-employed prefixes), hosts on the
local network will continue using stale prefixes for an unacceptably
long period of time, thus resulting in connectivity problems. This
document specifies improvements to Customer Edge Routers that help
mitigate the aforementioned problem for typical residential and small
office scenarios.
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
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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 September 10, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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(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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Improved Customer Edge Router Behavior . . . . . . . . . . . 2
2.1. Interface Between DHCPv6-PD and SLAAC . . . . . . . . . . 3
2.2. Signaling Stale Configuration Information . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In scenarios where network configuration information related to IPv6
prefixes becomes invalid without any explicit signaling of that
condition, nodes on the local network will continue using stale
prefixes for an unacceptably long period of time, thus resulting in
connectivity problems. This problem is documented in detail in
[I-D.gont-v6ops-slaac-renum].
This document specifies improvements to Customer Edge (CE) Routers
that help mitigate the aforementioned problem for residential or
small office scenarios.
2. Improved Customer Edge Router Behavior
This section specifies and clarifies requirements for Customer Edge
Routers -- particularly when they advertise with Stateless Address
Autoconfiguration (SLAAC) [RFC4862] prefixes learned via
DHCPv6-Prefix Delegation (DHCPv6-PD) [RFC8415] or prefixes derived
from them -- that can help mitigate the problem discussed in
Section 1. This would obviously make robustness dependent on the
Customer Edge Router (on which the user or ISP may have no control),
as opposed to the host itself.
The updated behaviour is as follows:
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o CE routers MUST signal stale configuration information as
specified in Section 2.2
o CE routers MUST implement the DHCPv6-PD/SLAAC interface specified
in Section 2.1
o CE routers SHOULD NOT automatically send DHCPv6-PD RELEASE
messages upon reboot events
2.1. Interface Between DHCPv6-PD and SLAAC
The "Preferred Lifetime" and "Valid Lifetime" of Prefix Information
Options (PIOs) [RFC4861] corresponding to prefixes learned via
DHCPv6-PD MUST NOT span past the lease time of the DHCPv6-PD
prefixes. This means that the advertised "Preferred Lifetime" and
"Valid Lifetime" MUST be dynamically adjusted such that the
advertised lifetimes never span past the lease time of the prefixes
delegated via DHCPv6-PD.
This is in line with these existing requirements from other
specifications, which we reference here for clarity:
o [RFC8415] specifies, in Section 6.3, that "if the delegated prefix
or a prefix derived from it is advertised for stateless address
autoconfiguration [RFC4862], the advertised preferred and valid
lifetimes MUST NOT exceed the corresponding remaining lifetimes of
the delegated prefix."
RATIONALE:
* The lifetime values employed for the "Preferred Lifetime"
(AdvPreferredLifetime) and "Valid Lifetime" (AdvValidLifetime)
should never be larger than the remaining lease time for the
corresponding prefix (as learned via DHCPv6-PD).
* The lifetime values advertised for prefixes corresponding to a
prefix leased via DHCPv6-PD should be dynamically updated
(rather than static values), since otherwise the advertised
lifetimes would eventually span past the DHCPv6-PD lease time.
2.2. Signaling Stale Configuration Information
In order to phase-out stale configuration information:
o A CE router sending RAs that advertise dynamically-learned
prefixes (e.g. via DHCPv6-PD) on an interface MUST record, on
stable storage, the list of prefixes being advertised on each
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network segment, and the "A" and "L" flags of the corresponding
PIOs.
o Upon changes to the advertised prefixes, and after bootstrapping,
the CE router advertising prefix information via SLAAC should
proceed as follows:
* Any prefixes that were previously advertised via Router
Advertisement (RA) messages, but that have now become stale,
MUST be advertised with a "Valid Lifetime" and a "Preferred
Lifetime" set to 0, and the "A" and "L" bits unchanged.
* The aforementioned advertisement SHOULD be performed for at
least the "Valid Lifetime" previously employed for such prefix.
The aforementioned improved behaviour assumes compliance with the
following existing requirements from other specifications, which we
reference here for clarity:
o [RFC7084] specifies (requirement LE-13, in Section 4.3) that when
the delegated prefix changes (i.e., the current prefix is replaced
with a new prefix without any overlapping time period), "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]"
3. IANA Considerations
This document has no actions for IANA.
4. Security Considerations
This document discusses a problem that may arise in scenarios where
dynamic IPv6 prefixes are employed, and proposes improvements to
Customer Edge Routers [RFC7084] to mitigate the problem for
residential or small office scenarios. It does not introduce new
security issues.
5. Acknowledgments
The authors would lie to thank (in alphabetical order) Mikael
Abrahamsson, Luis Balbinot, Tim Chown, Brian Carpenter, Owen DeLong,
Gert Doering, Steinar Haug, Nick Hilliard, Philip Homburg, Lee
Howard, Christian Huitema, Ted Lemon, Albert Manfredi, Jordi Palet
Martinez, Richard Patterson, Michael Richardson, Mark Smith, Job
Snijders, Tarko Tikan, and Ole Troan, for providing valuable comments
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on [I-D.gont-6man-slaac-renum], on which this document is
based.earlier versions of this document.
Fernando would like to thank Alejandro D'Egidio and Sander Steffann
for a discussion of these issues. Fernando would also like to thank
Brian Carpenter who, over the years, has answered many questions and
provided valuable comments that has benefited his protocol-related
work.
6. References
6.1. Normative References
[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>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
6.2. Informative References
[I-D.gont-6man-slaac-renum]
Gont, F., Zorz, J., and R. Patterson, "Improving the
Robustness of Stateless Address Autoconfiguration (SLAAC)
to Flash Renumbering Events", draft-gont-6man-slaac-
renum-02 (work in progress), February 2020.
[I-D.gont-v6ops-slaac-renum]
Gont, F., Zorz, J., and R. Patterson, "Reaction of
Stateless Address Autoconfiguration (SLAAC) to Flash-
Renumbering Events", draft-gont-v6ops-slaac-renum-02 (work
in progress), February 2020.
[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>.
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Authors' Addresses
Fernando Gont
SI6 Networks
Segurola y Habana 4310, 7mo Piso
Villa Devoto, Ciudad Autonoma de Buenos Aires
Argentina
Email: fgont@si6networks.com
URI: https://www.si6networks.com
Jan Zorz
Go6 Institute
Frankovo naselje 165
Skofja Loka 4220
Slovenia
Email: jan@go6.si
URI: https://www.go6.si
Richard Patterson
Sky UK
Email: richard.patterson@sky.uk
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