One document matched: draft-ietf-v6ops-6to4-to-historic-07.txt
Differences from draft-ietf-v6ops-6to4-to-historic-06.txt
v6ops WG O. Troan
Internet-Draft Cisco
Obsoletes: 3068 (if approved) B. Carpenter, Ed.
Intended status: Best Current Practice Univ. of Auckland
Expires: May 14, 2015 November 10, 2014
Deprecating Connection of IPv6 Domains via IPv4 Clouds (6to4)
draft-ietf-v6ops-6to4-to-historic-07.txt
Abstract
Experience with the "Connection of IPv6 Domains via IPv4 Clouds
(6to4)" IPv6 transition mechanism has shown that the mechanism is
unsuitable for widespread deployment and use in the Internet,
especially in its anycast mode. This document requests that RFC
3068, "An Anycast Prefix for 6to4 Relay Routers", be made obsolete
and moved to historic status. It also recommends that future
products should not support 6to4 anycast and that existing
deployments should be reviewed.
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 http://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 May 14, 2015.
Copyright Notice
Copyright (c) 2014 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
(http://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
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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.
1. Introduction
There would appear to be no evidence of any substantial deployment of
the variant of 6to4 described in [RFC3056]. Its extension specified
in "An Anycast Prefix for 6to4 Relay Routers" [RFC3068] has been
shown to have severe practical problems when used in the Internet.
This document requests that RFC 3068 be moved to Historic status as
defined in section 4.2.4 of [RFC2026].
6to4 was designed to help transition the Internet from IPv4 to IPv6.
It has been a good mechanism for experimenting with IPv6, but because
of the high failure rates seen with anycast 6to4 [HUSTON], end users
may end up disabling IPv6 on hosts as a result, and some content
providers have been reluctant to make content available over IPv6.
[RFC6343] analyses the known operational issues in detail and
describes a set of suggestions to improve 6to4 reliability, given the
widespread presence of hosts and customer premises equipment that
support it. However, experience shows that operational failures have
continued despite this advice being available. Fortunately the
advice to disable 6to4 by default has been widely adopted in recent
operating systems, and the failure modes have been largely hidden
from users by many browsers adopting the "happy eyeballs" approach
[RFC6555]. Nevertheless, operational problems caused by 6to4 still
occur.
IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) [RFC5969]
utilizes the same encapsulation and base mechanism as 6to4, and could
be viewed as a superset of 6to4 (6to4 could be achieved by setting
the 6rd prefix to 2002::/16). However, the deployment model is such
that 6rd can avoid the problems described here. In this sense, 6rd
can be viewed as superseding 6to4 as described in section 4.2.4 of
[RFC2026]
Given that native IPv6 support and reliable transition mechanisms
such as 6rd are now becoming common, the IETF sees no evolutionary
future for the 6to4 mechanism.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
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"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
3. 6to4 operational problems
6to4 is a mechanism designed to allow isolated IPv6 islands to reach
each other using IPv6 over IPv4 automatic tunneling. To reach the
native IPv6 Internet the mechanism uses relay routers both in the
forward and reverse direction. The mechanism is supported in many
IPv6 implementations. With the increased deployment of IPv6, the
mechanism has been shown to have a number of fundamental
shortcomings.
6to4 depends on relays both in the forward and reverse direction to
enable connectivity with the native IPv6 Internet. A 6to4 node will
send IPv4 encapsulated IPv6 traffic to a 6to4 relay, that is
connected both to the 6to4 cloud and to native IPv6. In the reverse
direction a 2002::/16 route is injected into the native IPv6 routing
domain to attract traffic from native IPv6 nodes to a 6to4 relay
router. It is expected that traffic will use different relays in the
forward and reverse direction. RFC 3068 adds an extension that
allows the use of a well known IPv4 anycast address to reach the
nearest 6to4 relay in the forward direction.
One model of 6to4 deployment, described in section 5.2 of RFC 3056,
suggests that a 6to4 router should have a set of managed connections
(via BGP connections) to a set of 6to4 relay routers. While this
makes the forward path more controlled, it does not guarantee a
functional reverse path. In any case this model has the same
operational burden as manually configured tunnels and has seen no
deployment in the public Internet.
List of some of the known issues with 6to4:
o Use of relays. 6to4 depends on an unknown third party to operate
the relays between the 6to4 cloud and the native IPv6 Internet.
o The placement of the relay can lead to increased latency, and in
the case the relay is overloaded, packet loss.
o There is generally no customer relationship between the end-user
and the relay operator, or even a way for the end-user to know who
the relay operator is, so no support is possible.
o A 6to4 relay for the reverse path and an anycast 6to4 relay used
for the forward path, are openly accessible, limited only by the
scope of routing. 6to4 relays can be used to anonymize traffic and
inject attacks into IPv6 that are very difficult to trace.
o 6to4 may silently discard traffic in the case where protocol (41)
is blocked in intermediate firewalls. Even if a firewall sent an
ICMP message unreachable back, an IPv4 ICMP message rarely
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contains enough of the original IPv6 packet so that it can be
relayed back to the IPv6 sender. That makes this problem hard to
detect and react upon by the sender of the packet.
o As 6to4 tunnels across the Internet, the IPv4 addresses used must
be globally reachable. RFC 3056 states that a private address
[RFC1918] MUST NOT be used. 6to4 will not work in networks that
employ other addresses with limited topological span. In
particular it will predictably fail in the case of double network
address translation (NAT444).
For further analysis, see [RFC6343].
Peer-to-peer usage of the 6to4 mechanism, not depending on the
anycast mechanism, might exist in the Internet, largely unknown to
operators. This is harmless to third parties and the current
document is not intended to prevent such traffic continuing.
4. Deprecation
This document formally deprecates the anycast 6to4 transition
mechanism defined in [RFC3068] and the associated anycast IPv4
address 192.88.99.1. It is NOT RECOMMENDED to include this mechanism
in new implementations. It is no longer considered to be a useful
service of last resort.
The prefix 192.88.99.0/24 MUST NOT be reassigned for other use except
by a future IETF standards action.
The basic unicast 6to4 mechanism defined in [RFC3056] and the
associated 6to4 IPv6 prefix 2002::/16 are not deprecated. The
default address selection rules specified in [RFC6724] are not
modified. However, if included in implementations, unicast 6to4 MUST
be disabled by default.
Implementations capable of acting as 6to4 routers MUST NOT enable
6to4 without explicit user configuration. In particular, enabling
IPv6 forwarding on a device MUST NOT automatically enable 6to4.
Current operators of an anycast 6to4 relay with the IPv4 address
192.88.99.1 SHOULD review the information in [RFC6343] and the
present document, and then consider carefully when the anycast relay
can be discontinued as traffic diminishes. Internet service
providers SHOULD filter out routes to 192.88.99.1.
Operators of a 6to4 return relay announcing the IPv6 prefix 2002::/16
SHOULD review the information in [RFC6343] and the present document,
and then consider carefully when the return relay can be discontinued
as traffic diminishes. As discussed in Section 4.5 of RFC 6343,
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content providers might choose to continue operating such a relay for
the benefit of their own residual 6to4 clients. Internet service
providers SHOULD announce the IPv6 prefix 2002::/16 if and only if it
leads to a correctly operating return relay as described in RFC 6343.
The references to the 6to4 relay anycast prefix (192.88.99.0/24)
should be removed as soon as practical from the revision of the
Special Use IPv4 addresses [RFC6890].
Incidental references to 6to4 should be reviewed and possibly removed
from other IETF documents if and when they are updated. These
documents include RFC3162, RFC3178, RFC3790, RFC4191, RFC4213,
RFC4389, RFC4779, RFC4852, RFC4891, RFC4903, RFC5157, RFC5245,
RFC5375, RFC5971, and RFC6071.
5. IANA Considerations
IANA is requested to mark the 192.88.99.0/24 prefix [RFC3068] as
"deprecated", pointing to this document. Redelegation of this prefix
for any usage requires justification via an IETF Standards Action
[RFC5226].
6. Security Considerations
There are no new security considerations pertaining to this document.
General security issues with tunnels are listed in [RFC6169] and more
specifically to 6to4 in [RFC3964] and [RFC6324].
7. Acknowledgements
The authors would like to acknowledge Tore Anderson, Dmitry Anipko,
Jack Bates, Cameron Byrne, Ben Campbell, Gert Doering, Ray Hunter,
Joel Jaeggli, Kurt Erik Lindqvist, Jason Livingood, Keith Moore, Tom
Petch, Daniel Roesen and Mark Townsley, James Woodyatt, for their
contributions and discussions on this topic.
Special thanks go to Fred Baker, Geoff Huston, and Wes George for
their significant contributions.
Many thanks to Gunter Van de Velde for documenting the harm caused by
non-managed tunnels and to stimulate the creation of this document.
8. References
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8.1. Normative References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
RFC 3068, June 2001.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153, RFC
6890, April 2013.
8.2. Informative References
[HUSTON] Huston, , "Flailing IPv6", December 2010,
<http://www.potaroo.net/ispcol/2010-12/6to4fail.html>.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.
[RFC3964] Savola, P. and C. Patel, "Security Considerations for
6to4", RFC 3964, December 2004.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification", RFC
5969, August 2010.
[RFC6169] Krishnan, S., Thaler, D., and J. Hoagland, "Security
Concerns with IP Tunneling", RFC 6169, April 2011.
[RFC6324] Nakibly, G. and F. Templin, "Routing Loop Attack Using
IPv6 Automatic Tunnels: Problem Statement and Proposed
Mitigations", RFC 6324, August 2011.
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[RFC6343] Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
RFC 6343, August 2011.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, April 2012.
Authors' Addresses
Ole Troan
Cisco
Oslo
Norway
Email: ot@cisco.com
Brian Carpenter (editor)
Department of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
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