Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis
RFC 7050
Internet Engineering Task Force (IETF) T. Savolainen
Request for Comments: 7050 Nokia
Category: Standards Track J. Korhonen
ISSN: 2070-1721 Broadcom
D. Wing
Cisco Systems
November 2013
Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis
Abstract
This document describes a method for detecting the presence of DNS64
and for learning the IPv6 prefix used for protocol translation on an
access network. The method depends on the existence of a well-known
IPv4-only fully qualified domain name "ipv4only.arpa.". The
information learned enables nodes to perform local IPv6 address
synthesis and to potentially avoid NAT64 on dual-stack and multi-
interface deployments.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7050.
Savolainen, et al. Standards Track [Page 1]
RFC 7050 Pref64::/n Discovery November 2013
Copyright Notice
Copyright (c) 2013 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Requirements Notation and Terminology ...........................4
2.1. Requirements Notation ......................................4
2.2. Terminology ................................................4
3. Node Behavior ...................................................4
3.1. Validation of Discovered Pref64::/n ........................6
3.1.1. DNSSEC Requirements for the Network .................7
3.1.2. DNSSEC Requirements for the Node ....................7
3.2. Connectivity Check .........................................8
3.2.1. No Connectivity Checks against "ipv4only.arpa." .....9
3.3. Alternative Fully Qualified Domain Names ..................10
3.4. Message Flow Illustration .................................10
4. Operational Considerations for Hosting the IPv4-Only
Well-Known Name ................................................12
5. Operational Considerations for DNS64 Operator ..................12
5.1. Mapping of IPv4 Address Ranges to IPv6 Prefixes ...........13
6. Exit Strategy ..................................................14
7. Security Considerations ........................................14
8. IANA Considerations ............................................15
8.1. Domain Name Reservation Considerations ....................15
8.2. IPv4 Address Allocation Considerations ....................16
8.3. IAB Statement Regarding This .arpa Request ................17
9. Acknowledgements ...............................................18
10. References ....................................................18
10.1. Normative References .....................................18
10.2. Informative References ...................................19
Appendix A. Example of DNS Record Configuration ..................20
Appendix B. About the IPv4 Address for the Well-Known Name .......21
Savolainen, et al. Standards Track [Page 2]
RFC 7050 Pref64::/n Discovery November 2013
1. Introduction
As part of the transition to IPv6, NAT64 [RFC6146] and DNS64
[RFC6147] technologies will be utilized by some access networks to
provide IPv4 connectivity for IPv6-only nodes [RFC6144]. DNS64
utilizes IPv6 address synthesis to create local IPv6 addresses for
peers having only IPv4 addresses, hence allowing DNS-using IPv6-only
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