Internet DRAFT - draft-ietf-v6ops-siit-eam
draft-ietf-v6ops-siit-eam
IPv6 Operations T. Anderson
Internet-Draft Redpill Linpro
Updates: 6145 (if approved) A. Leiva Popper
Intended status: Standards Track NIC Mexico
Expires: April 22, 2016 October 20, 2015
Explicit Address Mappings for Stateless IP/ICMP Translation
draft-ietf-v6ops-siit-eam-03
Abstract
This document extends the Stateless IP/ICMP Translation Algorithm
(SIIT) with an Explicit Address Mapping (EAM) algorithm, and formally
updates RFC 6145. The EAM algorithm facilitates stateless IP/ICMP
translation between arbitrary (non-IPv4-translatable) IPv6 endpoints
and IPv4.
Status of This Memo
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Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3. Explicit Address Mapping Algorithm . . . . . . . . . . . . . 5
3.1. Explicit Address Mapping Table . . . . . . . . . . . . . 5
3.2. Explicit Address Mapping Specification . . . . . . . . . 6
3.3. IP Address Translation Procedure . . . . . . . . . . . . 7
3.3.1. Address Translation Steps: IPv4 to IPv6 . . . . . . . 7
3.3.2. Address Translation Steps: IPv6 to IPv4 . . . . . . . 7
4. Hairpinning of IPv6 Traffic . . . . . . . . . . . . . . . . . 8
4.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 8
4.2. Recommendation . . . . . . . . . . . . . . . . . . . . . 9
4.2.1. Simple Hairpinning Support . . . . . . . . . . . . . 9
4.2.2. Intrinsic Hairpinning Support . . . . . . . . . . . . 9
5. Overlapping Explicit Address Mappings . . . . . . . . . . . . 10
6. Lack of Checksum Neutrality . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix A. Use Cases . . . . . . . . . . . . . . . . . . . . . 13
A.1. 464XLAT . . . . . . . . . . . . . . . . . . . . . . . . . 13
A.2. IVI . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
A.3. SIIT-DC . . . . . . . . . . . . . . . . . . . . . . . . . 14
Appendix B. Example IP Address Translations . . . . . . . . . . 15
B.1. Hairpinning Examples . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
The Stateless IP/ICMP Translation Algorithm (SIIT) [RFC6145]
specifies that when translating IPv4 addresses to IPv6 and vice
versa, all addresses must be translated using the algorithm specified
in [RFC6052]. This document specifies an alternative to the
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[RFC6052] algorithm, where IP addresses are translated according to a
table of Explicit Address Mappings configured on the stateless
translator. This removes the previous constraint that IPv6 nodes
that communicate with IPv4 nodes through SIIT must be configured with
IPv4-translatable IPv6 addresses.
Translation using the Explicit Address Mapping Table does not replace
[RFC6052]. For most use cases, it is expected that both algorithms
are used in concert. The Explicit Address Mapping algorithm is used
only when a mapping matching the address to be translated exists. If
no matching mapping exists, the [RFC6052] algorithm will be used
instead. Thus, when translating an individual IP packet, an SIIT
implementation might translate one of the two IP address fields
according to an EAM, while the other IP address field is translated
according to [RFC6052].
1.1. Terminology
This document makes use of the following terms:
EAM
An Explicit Address Mapping, as specified in Section 3.2.
EAMT
The Explicit Address Mapping Table, as specified in Section 3.1.
Inner (header or address)
Refers to an IP header located inside the payload of an ICMP error
packet, or to an IP address within that header. Compare "Outer".
Outer (header or address)
Refers to the first IP header in a packet, or to an IP address
within that header. In other words, an IP header or address that
is NOT "Inner". If a reference is made to an IP header or address
without the "Inner" or "Outer" qualifier, it should be considered
as "Outer".
SIIT
The Stateless IP/ICMP Translation algorithm, as specified in
[RFC6145].
XLAT
Short for "translation".
IPv4-converted IPv6 addresses
As defined in Section 1.3 of [RFC6052].
IPv4-translatable IPv6 addresses
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As defined in Section 1.3 of [RFC6052].
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 [RFC2119].
2. Problem Statement
Section 3.2.1 of [RFC6144] notes that "stateless translation
mechanisms typically put constraints on what IPv6 addresses can be
assigned to IPv6 nodes that want to communicate with IPv4
destinations using an algorithmic mapping". In practice, this means
that the IPv6 nodes must be configured with IPv4-translatable IPv6
addresses. For the reasons discussed below, some environments may
find that the use of IPv4-translatable IPv6 addresses is not desired
or even possible.
Limited availability:
The number of IPv4-translatable IPv6 addresses available to an
operator is equal to the number of IPv4 addresses that is assigned
to the SIIT function. IPv4 addresses are scarce, and as a result
an operator might not have enough IPv4-translatable IPv6 addresses
to number the entire IPv6 infrastructure.
Restricted format:
IPv4-translatable IPv6 addresses must conform to the format
specified in Section 2.2 of [RFC6052]. This format is not
compatible with other common IPv6 address formats, such as the
EUI-64 based IPv6 address format used by IPv6 Stateless Address
Autoconfiguration [RFC4862].
An operator could overcome the above two problems by building an IPv6
network using regular (non-IPv4-translatable) IPv6 addresses, and
assign IPv4-translatable IPv6 addresses as secondary addresses on the
nodes that want to communicate with IPv4 nodes through SIIT only.
However, doing so may result in a new set of undesired consequences:
Routing complexity:
The IPv4-translatable IPv6 addresses must be routed throughout the
IPv6 network separately from the primary (non-IPv4-translatable)
IPv6 addresses used by the nodes. It might be impossible to
aggregate these routes, as two adjacent IPv4-translatable IPv6
addresses might not be assigned to two adjacent IPv6 nodes. As a
result, in order to support SIIT, the IPv6 network might need to
carry a large number of extraneous routes. These routes must be
separately injected into the IPv6 routing topology somehow. Any
intermediate devices in the IPv6 network such as a firewall might
require special configuration in order to treat the
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IPv4-translatable IPv6 address the same as the primary IPv6
address, for example by requiring that any ACL entries involving
the primary IPv6 address of a node must be duplicated.
Operational complexity:
The IPv4-translatable IPv6 addresses not only have to be assigned
to the IPv6 nodes participating in SIIT; all applications and
services on those nodes must also be configured to use them. For
example, if the IPv6 node is a load balancer, it might require a
separate Virtual Server definition using the IPv4-translatable
IPv6 address in addition to one using the service's primary IPv6
address. A web server might require specific configuration to
listen for connections on both the IPv4-translatable and the
primary IPv6 address. A High-Availability cluster service must be
set up to fail over both addresses between cluster nodes, and
depending on how the IPv6 network learns the location of the
IPv4-translatable IPv6 address, the fail-over mechanism used for
the two addresses might be completely different. Service
monitoring must be done for both the IPv4-translatable and the
primary IPv6 address, and any trouble-shooting procedures must be
extended to involve both addresses. Finally, the Default Address
Selection Policy Table [RFC6724] on the IPv6 nodes might need to
be altered in order to ensure that outbound sessions towards the
IPv4 Internet are sourced from an IPv4-translatable IPv6 address.
In short, the use of IPv4-translatable IPv6 addresses in parallel
with regular IPv6 addresses is in many ways analogous to the use of
Dual Stack [RFC4213]. While no actual IPv4 packets are used, the
IPv4-translatable IPv6 addresses creates a secondary "stack" in the
infrastructure that must be treated and operated separately from the
primary one. This increases the complexity of the overall
infrastructure, in turn increasing operational overhead, and reducing
reliability. An operator who for such reasons finds the use Dual
Stack unappealing, might feel the same way about using SIIT with
IPv4-translatable IPv6 addresses.
3. Explicit Address Mapping Algorithm
This normative section defines the EAM algorithm, and formally
updates Section 4.1 and Section 5.1 of [RFC6145]. Specifically, when
the EAM algorithm is applied, it supplants [RFC6145]'s requirement
that a translator operating in the stateless mode must translate the
Source Address and Destination Address IP header fields according to
Section 2.3 of [RFC6052].
3.1. Explicit Address Mapping Table
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An SIIT implementation includes an EAMT, a conceptual table in which
each row represents an EAM. Each EAM describes a mapping between
IPv4 and IPv6 prefixes/addresses. An operator populates the EAMT to
provide the mappings between the two address families.
The EAMT consists of the following columns:
o IPv4 Prefix
o IPv6 Prefix
SIIT implementations MAY include other columns in order to support
proprietary extensions to the EAM algorithm.
Throughout this document, figures representing the EAMT contain an
Index column using the pound sign as the header. This column is not
a required part of this specification; it is included only as a
convenience to the reader.
3.2. Explicit Address Mapping Specification
An EAM consists of an IPv4 Prefix and an IPv6 Prefix. The prefix
length MAY be omitted, in which case the implementation MUST assume
it to be 32 for IPv4 and 128 for IPv6. Figure 1 illustrates an EAMT
containing examples of valid EAMs.
Example EAMT
+---+----------------+----------------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+----------------+----------------------+
| 1 | 192.0.2.1 | 2001:db8:aaaa:: |
| 2 | 192.0.2.2/32 | 2001:db8:bbbb::b/128 |
| 3 | 192.0.2.16/28 | 2001:db8:cccc::/124 |
| 4 | 192.0.2.128/26 | 2001:db8:dddd::/64 |
| 5 | 192.0.2.192/31 | 64:ff9b::/127 |
+---+----------------+----------------------+
Figure 1
An EAM's IPv4 Prefix value MUST have an identical or smaller number
of suffix bits than its corresponding IPv6 Prefix value.
Unless otherwise specified in Section 4, an SIIT implementation MUST
individually translate each IP address it encounters in the packet's
IP headers (including any IP headers contained within ICMP errors)
according to Section 3.3.
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3.3. IP Address Translation Procedure
This section describes step-by-step how an SIIT implementation
translates addresses between IPv4 and IPv6. Only the outcome of the
algorithm described should be considered normative, that is, an SIIT
implementation may implement the exact procedure differently than
what is described here, but the outcome of the algorithm MUST be the
same.
For concrete examples of IP addresses translations, refer to
Appendix B.
3.3.1. Address Translation Steps: IPv4 to IPv6
1. The IPv4 Prefix column of the EAMT is searched for the EAM entry
that shares the longest common prefix with the IPv4 address being
translated. The IPv4 Prefix and IPv6 Prefix values of the EAM
entry found is from now on referred to as EAM4 and EAM6,
respectively.
2. If no matching EAM entry is found, the EAM algorithm is aborted.
The SIIT implementation MUST proceed to translate the address in
accordance with [RFC6145] (and its updates).
3. The prefix bits of EAM4 are removed from IPv4 address being
translated. The remaining suffix bits from the IPv4 address
being translated are stored in a temporary buffer.
4. The prefix bits of EAM6 are prepended to the temporary buffer.
5. If the temporary buffer at this point does not contain a 128-bit
value, it is padded with trailing zeroes so that it reaches a
length of 128 bits.
6. The contents of the temporary buffer is the translated IPv6
address.
3.3.2. Address Translation Steps: IPv6 to IPv4
1. The IPv6 Prefix column of the EAMT is searched for the EAM entry
that shares the longest common prefix with the IPv6 address being
translated. The IPv4 Prefix and IPv6 Prefix values of the EAM
entry found is from now on referred to as EAM4 and EAM6,
respectively.
2. If no matching EAM entry is found, the EAM algorithm is aborted.
The SIIT implementation MUST proceed to translate the address in
accordance with [RFC6145] (and its updates).
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3. The prefix bits of EAM6 are removed from IPv6 address being
translated. The remaining suffix bits from the IPv6 address
being translated are stored in a temporary buffer.
4. The prefix bits of EAM4 are prepended to the temporary buffer.
5. If the temporary buffer at this point does not contain a 32-bit
value, any trailing bits are discarded so that the buffer is
reduced to a length of 32 bits.
6. The contents of the temporary buffer is the translated IPv4
address.
4. Hairpinning of IPv6 Traffic
4.1. Problem Statement
Two IPv6 nodes that are both covered by EAMs might in certain
circumstances attempt to communicate through a stateless translator,
rather than using native IPv6 directly. This happens if one of the
nodes initiate traffic towards the IPv4-converted IPv6 address whose
embedded IPv4 address matches an EAM that covers the other node.
Special consideration is required in order to make this communication
pattern work in a bi-directional fashion. This is illustrated by the
example below.
Assume that a stateless translator is configured with an [RFC6052]
translation prefix of 64:ff9b::/96 and the EAMT shown in Figure 1.
The IPv6 node 2001:db8:aaaa:: transmits an IPv6 packet towards
64:ff9b::192.0.2.2, which reaches the translator and is being
translated into an IPv4 packet with source address 192.0.2.1 and
destination address 192.0.2.2. This destination address is found in
the EAMT, so the packet loops back into the translation function, and
is translated back to an IPv6 packet with source address
2001:db8:aaaa:: and destination address 2001:db8:bbbb::b.
While this packet will reach its destination just fine, a problem
will occur when 2001:db8:bbbb::b responds to it. The response packet
will have a source address of 2001:db8:bbbb::b and a destination
address of 2001:db8:aaaa::, and will be routed directly to its
destination without being subjected to any form of translation.
Because the source address of this response packet (2001:db8:bbbb::b)
is not equal to the destination address of the initial outgoing
packet (64:ff9b::192.0.2.2), the packet will most likely be discarded
by 2001:db8:aaaa:: and bi-directional communication will most likely
fail.
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The above scenario could be made to work by ensuring that the
stateless translator is hairpinning the traffic in both directions.
Section 4.2 describes how this is accomplished. The resulting
address translations are demonstrated step-by-step in Appendix B.1.
4.2. Recommendation
An SIIT implementation SHOULD include a feature that ensures that
hairpinned IPv6 traffic is supported. The feature SHOULD be enabled
by default. The following two subsections describe two alternate
ways to implement this feature. An implementation MAY support both
approaches.
4.2.1. Simple Hairpinning Support
When the simple hairpinning feature is enabled, the translator
employs the following rules when translating from IPv4 to IPv6:
1. If the packet is not an ICMPv4 error: The EAM algorithm MUST NOT
be used in order to translate the source address in the IPv4
header.
2. If the packet is an ICMPv4 error: The EAM algorithm MUST NOT be
used when translating the destination address in the inner IPv4
header.
3. If the packet is an ICMPv4 error whose outer IPv4 source address
is equal to its inner IPv4 destination address: The EAM algorithm
MUST NOT be used in order to translate the source address in the
outer IPv4 header.
Rule #2 and #3 are cumulative.
The addresses in question MUST instead be translated according to
[RFC6145], as if they did not match any EAM.
4.2.2. Intrinsic Hairpinning Support
When the intrinsic hairpinning feature is enabled, the translator
employs the following rules when receiving an IPv6 packet:
If all the conditions in either of the two sets below is true, the
packet is to be hairpinned. The implementation MUST immediately
(i.e., prior to forwarding it to the IPv4 network) translate the
packet back to IPv6. During the second translation pass, the
behaviour specified in Section 4.2.1 MUST be applied, and the Hop
Limit field SHOULD NOT be decremented.
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Condition set A:
A1. The packet is not an ICMPv4 error
A2. The destination address was translated using the [RFC6052]
algorithm
A3. The destination address is found in the EAMT
Condition set B:
B1. The packet is an ICMPv4 error
B2. The inner source address was translated using the [RFC6052]
algorithm
B3. The inner source address is found in the EAMT
5. Overlapping Explicit Address Mappings
The algorithm specified in Section 3 relies on making a lookup in the
EAMT in order to find the EAM entry that shares the longest common
prefix with the address being translated. Operators should note that
configuring EAMs with overlapping or identical IPv4 or IPv6 Prefixes
in the EAMT may create configurations where the IPv4-to-IPv6 and IPv6
-to-IPv4 address translations will not be symmetric. This may in
some cases make bi-directional communication impossible.
The example EAMT in Figure 2 could be thought of as implementing IVI
(Appendix A.2) (EAM #1), but additionally with a single exception in
the style of SIIT-DC (Appendix A.3) (EAM #2). The IPv4 Prefixes of
the two EAMs overlap, while the IPv6 Prefixes do not. This results
in a situation where the IPv6 address 2001:db8:ffc6:3364:4000:: will
be translated (according to EAM #1) to the IPv4 address
198.51.100.64. However, when this IPv4 address is translated back to
IPv6, it will be translated (according to EAM #2) to the IPv6 address
2001:db8::abcd. Because the IPv4-to-IPv6 translation in this example
does not mirror the corresponding IPv6-to-IPv4 translation, bi-
directional communication involving the IPv6 address
2001:db8:ffc6:3364:4000:: might fail. In order to help avoid such
situations, implementations MAY warn the operator when a new EAM that
overlaps with a previously existing one is inserted into the EAMT.
EAMT containing overlapping IPv4 Prefixes
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+---+------------------+--------------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+------------------+--------------------+
| 1 | 0.0.0.0/0 | 2001:db8:ff00::/40 |
| 2 | 198.51.100.64/32 | 2001:db8::abcd/128 |
+---+------------------+--------------------+
Figure 2
In Figure 3, the IPv6 Prefixes of the two EAMs are identical. The
behaviour of the stateless translator when translating an IPv6 packet
that contains the address 2001:db8::1 to IPv4 is in this case
unspecified. In order to prevent this situation from occurring,
implementations MAY refuse to insert a new EAM, whose IPv4 or IPv6
Prefix value is identical to that of an already existing EAM, into
the EAMT.
EAMT containing identical IPv6 prefixes
+---+-----------------+-----------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+-----------------+-----------------+
| 1 | 198.51.100.8/32 | 2001:db8::1/128 |
| 2 | 198.51.100.9/32 | 2001:db8::1/128 |
+---+-----------------+-----------------+
Figure 3
6. Lack of Checksum Neutrality
When one or both of the address fields in an IP/ICMP packet are
translated according to EAM, the translation can not be relied upon
to be checksum neutral, even if the well-known prefix 64:ff9b::/96 is
used. This consideration is discussed in more detail in Section 4.1
of [RFC6052].
7. Security Considerations
The EAM algorithm does not introduce any new security issues beyond
those that are already discussed in Section 7 of [RFC6145].
8. IANA Considerations
This draft makes no request of the IANA.
9. Acknowledgements
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This document was conceived due to comments made by Dave Thaler in
the v6ops session at IETF 91 as well as e-mail discussions between
Fred Baker and the author.
Valuable reviews, suggestions, and other feedback was given by Fred
Baker, Mohamed Boucadair, Cameron Byrne, Brian E Carpenter, Brian
Haberman, Ray Hunter, Alvaro Retana, Michael Richardson, Dan
Romascanu, Hemant Singh, and Andrew Yourtchenko.
10. References
10.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<http://www.rfc-editor.org/info/rfc6052>.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, DOI 10.17487/RFC6145, April 2011,
<http://www.rfc-editor.org/info/rfc6145>.
10.2. Informative References
[I-D.ietf-v6ops-siit-dc]
Anderson, T., "SIIT-DC: Stateless IP/ICMP Translation for
IPv6 Data Centre Environments", draft-ietf-v6ops-siit-
dc-03 (work in progress), October 2015.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, DOI 10.17487/
RFC4213, October 2005,
<http://www.rfc-editor.org/info/rfc4213>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, DOI 10.17487/
RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, DOI 10.17487/RFC6144,
April 2011, <http://www.rfc-editor.org/info/rfc6144>.
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[RFC6219] Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
China Education and Research Network (CERNET) IVI
Translation Design and Deployment for the IPv4/IPv6
Coexistence and Transition", RFC 6219, DOI 10.17487/
RFC6219, May 2011,
<http://www.rfc-editor.org/info/rfc6219>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<http://www.rfc-editor.org/info/rfc6724>.
[RFC6791] Li, X., Bao, C., Wing, D., Vaithianathan, R., and G.
Huston, "Stateless Source Address Mapping for ICMPv6
Packets", RFC 6791, DOI 10.17487/RFC6791, November 2012,
<http://www.rfc-editor.org/info/rfc6791>.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation", RFC
6877, DOI 10.17487/RFC6877, April 2013,
<http://www.rfc-editor.org/info/rfc6877>.
[RFC7335] Byrne, C., "IPv4 Service Continuity Prefix", RFC 7335, DOI
10.17487/RFC7335, August 2014,
<http://www.rfc-editor.org/info/rfc7335>.
Appendix A. Use Cases
The following subsections lists some use cases that at the time of
writing leverage SIIT with the EAM algorithm.
A.1. 464XLAT
When the CLAT component in the 464XLAT [RFC6877] architecture does
not have a dedicated IPv6 prefix assigned, it may instead use "one
interface IPv6 address that is claimed by the CLAT". This IPv6
address might not be IPv4-translatable. If this is the case, the
CLAT essentially implements the EAM algorithm using an EAMT as
follows (assuming the CLAT's IPv4 address is picked from the IPv4
Service Continuity Prefix [RFC7335]):
Example EAMT for an 464XLAT CLAT
+---+--------------+-------------------------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+--------------+-------------------------------+
| 1 | 192.0.0.1/32 | CLAT_claimed_IPv6_address/128 |
+---+--------------+-------------------------------+
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Figure 4
In this particular use case, the EAM algorithm is used to translate
IPv6 destination addresses to IPv4, and conversely, IPv4 source
addresses to IPv6. Other addresses are translated using [RFC6052].
A.2. IVI
IVI [RFC6219] describes a stateless translation model that embeds
IPv4 addresses in a 40-bit translation prefix where bits 33-40 are
required to be 1. The embedded IPv4 address is located in bits 41-72
of the IPv6 address. Bits 73-128 are required to be 0.
The location of the eight least significant IPv4 address bits makes
the IVI address mapping differ from [RFC6052].
Example EAMT for IVI
+---+-------------+--------------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+-------------+--------------------+
| 1 | 0.0.0.0/0 | 2001:db8:ff00::/40 |
+---+-------------+--------------------+
Figure 5
In this particular use case, all addresses are translated according
to the EAM algorithm. In other words, [RFC6052] mapping is not used
at all.
A.3. SIIT-DC
SIIT-DC [I-D.ietf-v6ops-siit-dc] describes the use of SIIT to
facilitate connectivity from the IPv4 Internet to services hosted in
an IPv6-only data centre. In order to avoid the constraints relating
to the use of IPv4-translatable IPv6 addresses discussed in Section 2
the stateless IPv4/IPv6 translators are provisioned with an EAMT
containing one entry per IPv6-only service that are to be made
available from the IPv4 Internet, for example (assuming
2001:db8:aaaa::1 and 2001:db8:bbbb::1 are assigned to load balancers
or servers that provides the IPv6-only services in question):
Example EAMT for SIIT-DC
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+---+----------------+----------------------+
| # | IPv4 Prefix | IPv6 Prefix |
+---+----------------+----------------------+
| 1 | 203.0.113.1/32 | 2001:db8:aaaa::1/128 |
| 2 | 203.0.113.2/32 | 2001:db8:bbbb::1/128 |
+---+----------------+----------------------+
Figure 6
In this particular use case, the EAM algorithm is used to translate
IPv4 destination addresses to IPv6, and conversely, IPv6 source
addresses to IPv4. Other addresses are translated using [RFC6052].
Appendix B. Example IP Address Translations
Figure 7 demonstrates how a set of example IP addresses are
translated given the example EAMT in Figure 1. Implementors may use
the examples given to develop test cases to validate correct
operation. Note that the address translations are bidirectional, so
a single row in the table describes two address translations: IPv4 to
IPv6, and IPv6 to IPv4.
It is also assumed that the [RFC6052] translation prefix is
configured to be 64:ff9b::/96.
Example IP Address Translations
+--------------+------------------------+-----------------------+
| IPv4 Address | IPv6 Address | Comment |
+--------------+------------------------+-----------------------+
| 192.0.2.1 | 2001:db8:aaaa:: | According to EAM #1 |
| 192.0.2.2 | 2001:db8:bbbb::b | According to EAM #2 |
| 192.0.2.16 | 2001:db8:cccc:: | According to EAM #3 |
| 192.0.2.24 | 2001:db8:cccc::8 | According to EAM #3 |
| 192.0.2.31 | 2001:db8:cccc::f | According to EAM #3 |
| 192.0.2.128 | 2001:db8:dddd:: | According to EAM #4 |
| 192.0.2.152 | 2001:db8:dddd:0:6000:: | According to EAM #4 |
| 192.0.2.183 | 2001:db8:dddd:0:dc00:: | According to EAM #4 |
| 192.0.2.191 | 2001:db8:dddd:0:fc00:: | According to EAM #4 |
| 192.0.2.193 | 64:ff9b::1 | According to EAM #5 |
| 192.0.2.200 | 64:ff9b::c000:2c8 | According to RFC 6052 |
+--------------+------------------------+-----------------------+
Figure 7
B.1. Hairpinning Examples
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The following examples show how hairpinned IPv6 packets between the
IPv6 nodes 2001:db8:aaaa:: and 2001:db8:bbbb::b are translated
according to Section 4. As in Appendix B, the EAMT in Figure 1 is
used and the [RFC6052] translation prefix is 64:ff9b::/96. In
addition, the [RFC6791] pool is assumed to contain only the single
address 198.51.100.1.
Hairpinning of a normal IPv6 packet
+--------------+--------------------+---------------------+
| XLAT Stage | Source Address | Destination Address |
+--------------+--------------------+---------------------+
| Initial | 2001:db8:aaaa:: | 64:ff9b::192.0.2.2 |
+--------------+--------------------+---------------------+
| Intermediate | 192.0.2.1 | 192.0.2.2 |
+--------------+--------------------+---------------------+
| Final | 64:ff9b::192.0.2.1 | 2001:db8:bbbb::b |
+--------------+--------------------+---------------------+
Figure 8
Figure 8 illustrates how a normal (i.e., not an ICMP error) IPv6
packet sent from 2001:db8:aaaa:: towards 64:ff9b::192.0.2.2 is is
hairpinned. In this example, rule #1 in Section 4.2.1 was applied in
order to disable the EAM algorithm when translating the intermediate
IPv4 source address to IPv6.
Hairpinning of a router-originated ICMPv6 error
+--------------+-------+-----------------------+--------------------+
| XLAT Stage | Loc. | Source Address | Destination Addr. |
+--------------+-------+-----------------------+--------------------+
| Initial | Outer | 2001:db8::1234 | 64:ff9b::192.0.2.1 |
| | Inner | 64:ff9b::192.0.2.1 | 2001:db8:bbbb::b |
+--------------+-------+-----------------------+--------------------+
| Intermediate | Outer | 198.51.100.1 | 192.0.2.1 |
| | Inner | 192.0.2.1 | 192.0.2.2 |
+--------------+-------+-----------------------+--------------------+
| Final | Outer | 64:ff9b::198.51.100.1 | 2001:db8:aaaa:: |
| | Inner | 2001:db8:aaaa:: | 64:ff9b::192.0.2.2 |
+--------------+-------+-----------------------+--------------------+
Figure 9
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Figure 9 illustrates the hairpinning of an ICMPv6 error sent by an
arbitrary IPv6 router (2001:db8::1234) in response to the packet
Figure 8. In this example, rule #2 in Section 4.2.1 was applied in
order to disable the EAM algorithm when translating the intermediate
inner IPv4 destination address to IPv6.
Hairpinning of a host-originated ICMPv6 error
+--------------+-------+--------------------+--------------------+
| XLAT Stage | Loc. | Source Address | Destination Addr. |
+--------------+-------+--------------------+--------------------+
| Initial | Outer | 2001:db8:bbbb::b | 64:ff9b::192.0.2.1 |
| | Inner | 64:ff9b::192.0.2.1 | 2001:db8:bbbb::b |
+--------------+-------+--------------------+--------------------+
| Intermediate | Outer | 192.0.2.2 | 192.0.2.1 |
| | Inner | 192.0.2.1 | 192.0.2.2 |
+--------------+-------+--------------------+--------------------+
| Final | Outer | 64:ff9b::192.0.2.2 | 2001:db8:aaaa:: |
| | Inner | 2001:db8:aaaa:: | 64:ff9b::192.0.2.2 |
+--------------+-------+--------------------+--------------------+
Figure 10
Figure 10 illustrates the hairpinning of an ICMPv6 error sent by the
original destination host itself in response to the packet Figure 8.
In this example, rules #2 and #3 in Section 4.2.1 were both applied
in order to disable the EAM algorithm when translating the
intermediate inner IPv4 destination address and the intermediate
outer IPv4 destination address to IPv6.
Hairpinning of normal response packet
+--------------+--------------------+---------------------+
| XLAT Stage | Source Address | Destination Address |
+--------------+--------------------+---------------------+
| Initial | 2001:db8:bbbb::b | 64:ff9b::192.0.2.1 |
+--------------+--------------------+---------------------+
| Intermediate | 192.0.2.2 | 192.0.2.1 |
+--------------+--------------------+---------------------+
| Final | 64:ff9b::192.0.2.2 | 2001:db8:aaaa:: |
+--------------+--------------------+---------------------+
Figure 11
Figure 11 illustrates how 2001:db8:bbbb::b's response to the packet
in Figure 8 is hairpinned in the exact same fashion as the initial
packet. Again, rule #1 in Section 4.2.1 was applied in order to
disable the EAM algorithm when translating the intermediate IPv4
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source address to IPv6. The example is included in order to
illustrate how the addresses in the packet initially sent by
2001:db8:aaaa:: matches those in the translated response packet sent
by 2001:db8:bbbb::b, thus facilitating bi-directional communication.
Authors' Addresses
Tore Anderson
Redpill Linpro
Vitaminveien 1A
0485 Oslo
Norway
Phone: +47 959 31 212
Email: tore@redpill-linpro.com
URI: http://www.redpill-linpro.com
Alberto Leiva Popper
NIC Mexico
Av. Eugenio Garza Sada 427 L4-6
Monterrey, Nuevo Leon 64840
Mexico
Email: ydahhrk@gmail.com
URI: http://www.nicmexico.mx/
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