Updates to DNS64 Functionality Advertisement for DNS RA Option
draft-ma-6man-ra-dns64-flag-00

IPv6 Maintenance                                                   C. Ma
Internet-Draft                                                    C. Xie
Intended status: Standards Track                           China Telecom
Expires: 2 March 2026                                     29 August 2025

     Updates to DNS64 Functionality Advertisement for DNS RA Option
                     draft-ma-6man-ra-dns64-flag-00

Abstract

   This document defines a new flag in the DNS RA Option to advertise
   the DNS64 functionality.  This extension enables automatic
   configuration of DNS64 resolution, improving deployability in IPv6
   transition scenarios.

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   This Internet-Draft will expire on 2 March 2026.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  DNS64 Flag  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   DNS Extensions for Network Address Translation from IPv6 clients to
   IPv4 servers (DNS64)[RFC6147] is a widely deployed mechanism for
   IPv6-only networks requiring access to IPv4-only services.
   [I-D.ma-v6ops-5g-ipv6only]introduce the reasons for using RA to
   deliver DNS64 address configuration.  This document defines a new
   flag in the DNS RA option[RFC8106] to communicate DNS64 server
   address to hosts.

1.1.  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.

2.  DNS64 Flag

   Based on [RFC8106], this specification introduces a 'T' flag bit
   allocated in the leftmost bit of the Reserved field to signal the
   presence of DNS64 server addresses in the option payload.  Figure 1
   shows the format of the DNS64 option.

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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |T|         Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Lifetime                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |            DNS64 Server Address(es) (128-bit IPv6)            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Figure 1:DNS64 RA Option format

   Fields:

   *  Type: 8-bit identifier: 25

   *  Length: 8-bit unsigned integer.

   *  Flag T: 1-bit integer. set to indicate DNS64 server addresses are
      in the option payload.

   *  Lifetime: 32-bit unsigned integer.

   *  DNS64 Server Address(es): One or more 128-bit IPv6 addresses of
      the DNS64.

3.  Security Considerations

   This memo does not introduce any new security problems.
   Considerations are described in Section 7 in [RFC8106]

4.  IANA Considerations

   This document requests allocation for the Flag T.

5.  Acknowledgements

   The comments and suggestions of the following are gratefully
   acknowledged:

6.  References

6.1.  Normative References

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   [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>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <https://www.rfc-editor.org/info/rfc4861>.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              DOI 10.17487/RFC6147, April 2011,
              <https://www.rfc-editor.org/info/rfc6147>.

   [RFC8106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 8106, DOI 10.17487/RFC8106, March 2017,
              <https://www.rfc-editor.org/info/rfc8106>.

   [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>.

6.2.  Informative References

   [I-D.ma-v6ops-5g-ipv6only]
              Ma, C. and C. Xie, "Considerations of Gradual IPv6-only
              Deployment in 5G Mobile Networks", Work in Progress,
              Internet-Draft, draft-ma-v6ops-5g-ipv6only-00, 26 February
              2025, <https://datatracker.ietf.org/doc/html/draft-ma-
              v6ops-5g-ipv6only-00>.

Authors' Addresses

   Chenhao Ma
   China Telecom
   Beiqijia Town, Changping District
   Beijing
   102209
   China
   Email: machh@chinatelecom.cn

   Chongfeng Xie
   China Telecom
   Beiqijia Town, Changping District

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   Beijing
   102209
   China
   Email: xiechf@cernet.edu.cn

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