ICMP Extensions for IP/ICMP translators (XLATs)
draft-equinox-intarea-icmpext-xlat-source-00
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| Authors | David Lamparter , Jen Linkova | ||
| Last updated | 2024-03-21 | ||
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draft-equinox-intarea-icmpext-xlat-source-00
Internet Area D. Lamparter
Internet-Draft NetDEF, Inc.
Intended status: Standards Track J. Linkova
Expires: 22 September 2024 Google
21 March 2024
ICMP Extensions for IP/ICMP translators (XLATs)
draft-equinox-intarea-icmpext-xlat-source-00
Abstract
This document suggests the creation of an ICMP Multi-part Extension
to carry the original IPv6 source address of ICMPv6 messages
translated to ICMP by stateless (RFC6145) or stateful (RFC 6146)
protocol translators.
About This Document
This note is to be removed before publishing as an RFC.
Source, version control history, and issue tracker for this draft can
be found at https://github.com/eqvinox/icmpext-clat-source.
(Note the draft was renamed (clat → xlat) prior to submission but
changing the repository name on github breaks too many things to be
worth the effort.)
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 22 September 2024.
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Copyright Notice
Copyright (c) 2024 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 (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 Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Improved Translation Behavior . . . . . . . . . . . . . . . . 3
4. IPv6 Original Source Extension . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
To allow communication between IPv6-only and IPv4-only devices, IPv4/
IPv6 translators translate IPv6 and IPv4 packet headers according to
the IP/ICMP Translation Algorithm defined in [RFC6145]. For example,
464XLAT ([RFC6877]) defines an architecture for providing IPv4
connectivity across an IPv6-only network. The solution contains two
key elements: provider-side translator (PLAT) and customer-side
translator (CLAT). CLAT implementations translate private IPv4
addresses to global IPv6 addresses, and vice versa, as defined in
[RFC6145].
To map IPv4 addresses to IPv6 ones the translators use the
translation prefix (either a well-known or a network-specific one,
see [RFC6052]). The resulting IPv6 addresses can be statelessly
translated back to IPv4. However it's not the case for an arbitrary
global IPv6 addresses. Those addresses can only be translated to
IPv4 by a stateful translators.
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One of scenarios when it might be required but not currently possible
is translating ICMPv6 error messages send by intermediate nodes to
the CLAT address in the 464XLAT envinronment. The most typical
example is a diagnistic tool like traceroute sending packets to an
IPv4 destination from an IPv6-only host. Received ICMPv6 Time
Exceeded are translated to ICMP Time Exceeded. If those packets were
originated from an IPv4 address and translated to ICMPv6 by the PLAT
(NAT64) device, then the source address of such packet can be mapped
back to IPv4 by removing the translation prefix. However ICMPv6
error messages sent by devices located between the IPv6-only host and
the NAT64 device have "native" IPv6 source addresses, which can not
be mapped back to IPv4. Those packets are usually dropped and tools
like traceroute can not represent IPv6 intermediate hops in any
meaningful way. Such behaviour complicates troubleshooting. It's
also confusing for users and increases operational costs, as users
report packet loss in the network based on traceroute output.
Some CLAT implementations are known to workaround this issue by
representing IPv6 addresses in IPv4 traceroute by using a reserved
IPv4 address space and using the hop limit as the last octet, so an
IPv6 device 5 hops away is shown as 225.0.0.5 etc.
It should be noted that the similar issue occurs in IPv6 Data Center
Environments when an ICMPv6 error message needs to be sent to an
IPv4-only client. As per Section 4.8 of [RFC7755], ICMPv6 error
packets are usually dropped by the translator.
This document proposes an ICMP extension so original IPv6 address of
an ICMPv6 error message can be included into IMCP message and
therefore passed to an application.
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. Improved Translation Behavior
Whenever a translator generates an IPv4 ICMP message from an ICMPv6
packet, and the IPv6 source address does not match the NAT64 prefix
(and is therefore not mappable to an IPv4 address), the extension
described in this document SHOULD be added to the ICMP packet.
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The translator SHOULD NOT add the extension if the packet IPv6 source
address is an IPv4 address mapped to an IPv6 address using the
translation prefix known to the translator.
TBD: clarify IPv4 source address for consistency? (maybe not, would
extend scope of this draft.)
4. IPv6 Original Source Extension
The suggested encoding to be appended[RFC4884] to ICMP messages is as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length = 20 | Class TBD1 | C-Type = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| original IPv6 source address |
+ 16 octets +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
The Length, Class and C-Type fields are as defined in [RFC4884] and
filled in accordingly. This document describes only one encoding and
uses C-Type 0 for it. C-Type MUST be set to 0 when appending this
extension. On receipt, this extension MUST be ignored if C-Type is
not 0 or if Length is not 20.
The original IPv6 source address field is always 16 octets in length
and filled as described in this document. It may contain any source
address possibly seen in an ICMPv6 packet. This notably includes
link-local addresses, the IPv6 loopback address, and mapped IPv4
addresses. Receivers MUST NOT reject addresses solely due to the
address not being a globally scoped IPv6 addresses.
5. Security Considerations
TBD. Should probably be local-only.
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6. Privacy Considerations
TBD
7. IANA Considerations
This document requests that IANA allocates a "Class Value" from the
"ICMP Extension Object Classes and Class Sub-types" registry created
by [RFC4884] for use as described above. The following entry should
be appended:
+=============+==============================+=================+
| Class Value | Class Name | Reference |
+=============+==============================+=================+
| TBD1 | Original IPv6 Source Address | [THIS DOCUMENT] |
+-------------+------------------------------+-----------------+
Table 1
8. References
8.1. 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>.
[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884,
DOI 10.17487/RFC4884, April 2007,
<https://www.rfc-editor.org/info/rfc4884>.
[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,
<https://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,
<https://www.rfc-editor.org/info/rfc6145>.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation",
RFC 6877, DOI 10.17487/RFC6877, April 2013,
<https://www.rfc-editor.org/info/rfc6877>.
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[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>.
8.2. Informative References
[RFC7755] Anderson, T., "SIIT-DC: Stateless IP/ICMP Translation for
IPv6 Data Center Environments", RFC 7755,
DOI 10.17487/RFC7755, February 2016,
<https://www.rfc-editor.org/info/rfc7755>.
Acknowledgements
This document is the result of discussions with Thomas Jensen.
Authors' Addresses
David 'equinox' Lamparter
NetDEF, Inc.
San Jose,
United States of America
Email: equinox@diac24.net, equinox@opensourcerouting.org
Jen Linkova
Google
1 Darling Island Rd
Pyrmont NSW 2009
Australia
Email: furry13@gmail.com, furry@google.com
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