v6ops WG O. Troan
Internet-Draft G. Van de Velde
Obsoletes: 3056 (if approved) Cisco
Intended status: Standards Track March 10, 2011
Expires: September 11, 2011
Request to move Connection of IPv6 Domains via IPv4 Clouds (6to4) to
Historic status
draft-troan-v6ops-6to4-to-historic-01.txt
Abstract
Experience with the "Connection of IPv6 Domains via IPv4 Clouds
(6to4)" IPv6 transitioning mechanism has shown that the mechanism is
unsuitable for widespread deployment and use in the Internet. This
document requests that RFC3056 and the companion document "An Anycast
Prefix for 6to4 Relay Routers" RFC3068 are moved to historic status.
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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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 11, 2011.
Copyright Notice
Copyright (c) 2011 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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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
The IPv6 transitioning mechanism "Connection of IPv6 Domains via IPv4
Clouds (6to4) described in [RFC3056] and the extension in "An Anycast
Prefix for 6to4 Relay Routers" RFC3068 [RFC3068] have been shown to
have severe practical problems being used in the Internet. This
document requests that RFC3056 and RFC3068 be moved to Historic
status as defined in section 4.2.4 [RFC2026].
See also the document Non-Managed IPv6 Tunnels considered Harmful
[I-D.vandevelde-v6ops-harmful-tunnels] for details.
[I-D.kuarsingh-v6ops-6to4-provider-managed-tunnel] are proposing a
mechanism using IPv6 NAT to solve the 6to4 reverse path problem.
[I-D.carpenter-v6ops-6to4-teredo-advisory] are proposing a set of
suggestions to improve 6to4 reliability.
Declaring the mechanism historic is not expected to have immediate
product implications. The IETF sees no evolutionary future for the
mechanism and it is not recommended to include this mechanism in new
implementations.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "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
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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. RFC3068 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 as described in section 5.2, RFC3056,
suggests that a 6to4 router should have a set of managed connections
(read BGP peers) to a set of 6to4 relay routers. While this makes
the forward path more controlled, it does not help the reverse path.
In any case this model has the same operational burden has manually
configured tunnels and has seen no deployment in the public Internet.
6to4 issues:
o Use of relays. 6to4 depends on the charity of an unknown third-
party to operate the relays between the 6to4 cloud and the native
IPv6 Internet. With the use of mechanism specified in [RFC3068]
in both directions, without it only in the reverse direction (from
native to 6to4) [RFC3056].
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 or even a way for the
end-user to know who the relay operator is, so no support is
possible.
o In case of the reverse path 6to4 relay and the anycast forward
6to4 relay, these have to be open for any address. Only limited
by the scope of the routing advertisement. 6to4 relays can be used
to anonymize traffic and inject attacks into IPv6 that are very
difficult to trace.
o 6to4 has no specified mechanism to handle the case where the
protocol (41) is blocked in intermediate firewalls. It can not be
expected that path MTU discovery across the Internet works
reliably; ICMP messages may be blocked and in any case an IPv4
ICMP message rarely has enough of the original packet in it to be
useful to proxy back to the IPv6 sender.
o As 6to4 tunnels across the Internet, the IPv4 addresses used must
be globally reachable. RFC3056 states that a private address
[RFC1918] MUST NOT be used. 6to4 will not work in networks that
employ addresses with limited topological span.
4. Recommendations for 6to4 Relay Operators
See [I-D.carpenter-v6ops-6to4-teredo-advisory].
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5. Recommendations for implementors
If the implementation continues to support 6to4, then the 6to4
functionality MUST NOT be enabled by default.
If the implementation continues to support 6to4, then the Source
Address Selection algorithm [RFC3484] MUST use a 6to4 address as a
last resort. I.e. only use it the node has no other means of IPv6
connectivity and the destination is IPv6 only.
6. IANA Considerations
This specification does not require any IANA actions.
7. Security Considerations
There are no new security considerations pertaining to this document.
General security issues with tunnels are listed in
[I-D.ietf-v6ops-tunnel-security-concerns] and more specifically to
6to4 in [I-D.ietf-v6ops-tunnel-loops] and
[I-D.vandevelde-v6ops-harmful-tunnels].
8. Acknowledgements
The authors would like to acknowledge Fred Baker, Jack Bates, Cameron
Byrne, Brian Carpenter, Gert Doering, Joel Jaeggli, Jason Livingood,
Keith Moore, Daniel Roesen and Mark Townsley, for their contributions
and discussions on this topic.
9. References
9.1. Normative References
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[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
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via IPv4 Clouds", RFC 3056, February 2001.
[RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
RFC 3068, June 2001.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
9.2. Informative References
[I-D.carpenter-v6ops-6to4-teredo-advisory]
Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
draft-carpenter-v6ops-6to4-teredo-advisory-02 (work in
progress), February 2011.
[I-D.ietf-v6ops-tunnel-loops]
Nakibly, G. and F. Templin, "Routing Loop Attack using
IPv6 Automatic Tunnels: Problem Statement and Proposed
Mitigations", draft-ietf-v6ops-tunnel-loops-04 (work in
progress), March 2011.
[I-D.ietf-v6ops-tunnel-security-concerns]
Krishnan, S., Thaler, D., and J. Hoagland, "Security
Concerns With IP Tunneling",
draft-ietf-v6ops-tunnel-security-concerns-04 (work in
progress), October 2010.
[I-D.kuarsingh-v6ops-6to4-provider-managed-tunnel]
Kuarsingh, V., Lee, Y., and O. Vautrin, "6to4 Provider
Managed Tunnels",
draft-kuarsingh-v6ops-6to4-provider-managed-tunnel-01
(work in progress), February 2011.
[I-D.vandevelde-v6ops-harmful-tunnels]
Velde, G., Troan, O., and T. Chown, "Non-Managed IPv6
Tunnels considered Harmful",
draft-vandevelde-v6ops-harmful-tunnels-01 (work in
progress), August 2010.
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Authors' Addresses
Ole Troan
Cisco
Oslo,
Norway
Email: ot@cisco.com
Gunter Van de Velde
Cisco
De Kleetlaan 6a
Diegem 1831
Belgium
Phone: +32 2704 5473
Email: gvandeve@cisco.com
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