Internet DRAFT - draft-momoka-v6ops-ipv6-only-resolver
draft-momoka-v6ops-ipv6-only-resolver
v6ops 山本 桃歌 (M. Yamamoto)
Internet-Draft The University of Tokyo/WIDE Project
Intended status: Informational 豊田 安信 (Y. Toyota)
Expires: 11 March 2024 Keio University/WIDE Project
8 September 2023
IPv6-only Capable Resolvers Utilising NAT64
draft-momoka-v6ops-ipv6-only-resolver-02
Abstract
This document outlines how IPv6-only iterative resolvers can use
stateful NAT64 to establish communications with IPv4-only
authoritative servers. It outlines a mechanism for translating the
IPv4 addresses of authoritative servers to IPv6 addresses to initiate
communications. Through the mechanism of IPv4-to-IPv6 address
translation, these resolvers can operate in an IPv6-only network
environment.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the IPv6 Operations
Working Group mailing list (v6ops@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/v6ops/.
Source for this draft and an issue tracker can be found at
https://github.com/momoka0122y/draft-momoka-ipv6-only-resolver.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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 11 March 2024.
Yamamoto & Toyota Expires 11 March 2024 [Page 1]
Internet-Draft IPv6-only Resolver September 2023
Copyright Notice
Copyright (c) 2023 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
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation and Problem Solved . . . . . . . . . . . . . . . . 3
3.1. Deployment Scenarios and Examples . . . . . . . . . . . . 4
4. Solution with Existing Protocols . . . . . . . . . . . . . . 5
4.1. Finding an Authoritative Server with only IPv4
addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Generating IPv4-converted IPv6 Addresses . . . . . . . . 6
4.2.1. Obtaining the Pref64::/n of a NAT64 . . . . . . . . . 6
4.2.2. Performing Address Synthesis . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
This document describes how an IPv6-only iterative resolver can use
stateful NAT64 [NAT64] to connect to an IPv4-only authoritative
server by performing IPv4-to-IPv6 address translation [RFC6052] when
generating a query. When a specific DNS zone is only served by an
IPv4-only authoritative server (which has only an A record), an
IPv6-only iterative resolver cannot resolve that zone due to having
no access to an IPv4 network. However, by performing IPv4-to-IPv6
address translation and utilising the stateful NAT64, it will be
possible to access an IPv4-only authoritative server.
Yamamoto & Toyota Expires 11 March 2024 [Page 2]
Internet-Draft IPv6-only Resolver September 2023
This document is meant to exemplify how existing tools can be used to
allow IPv6-only resolvers to reach IPv4-only resolvers. DNS is thus
seen as an application that uses NAT64.
The document focuses on the exchanges between iterative resolvers and
authoritative resolvers but can be generalized to cover
communications between IPv6-only recursive resolvers and IPv4-only
resolvers.
2. Terminology
* Iterative resolver: A DNS server that repeatedly makes non-
recursive queries and follows referrals and/or aliases, as defined
in DNS Terminology [RFC8499]
* IPv6-only iterative resolvers: Iterative resolvers with only IPv6
connectivity.
* IPv6/IPv4 translator: A function that translates IPv6 packets to
IPv4 packets and vice versa. It is only required that the
communication initiated from the IPv6 side be supported.
* IPv4-only authoritative server: An authoritative server that
either has only IPv4 connectivity or is registered with only an A
record, making it accessible solely via IPv4.
3. Motivation and Problem Solved
An iterative resolver is one of the applications that require IPv4
connectivity. As stated in BCP91 [RFC3901], “every recursive name
server SHOULD be either IPv4-only or dual stack.” This is because
some authoritative servers do not support IPv6. As of 2023, even
some of the most frequently queried authoritative servers cannot be
accessed via IPv6. Without the utilization of an IPv6/IPv4
translation mechanism, IPv6-only resolvers need to forward queries to
a dual-stack recursive name server performing the iterative queries.
The current situation where an iterative resolver cannot operate
without IPv4 reachability may hinder the operation of a network's own
iterative resolver in an IPv6-only network. Therefore, this document
describes how iterative resolvers can be used without issues in
IPv6-only networks by utilising NAT64 as an IPv6/IPv4 translation
mechanism.
The NAT64/DNS64 mechanisms enable IPv6-only clients in an IPv6-only
network to communicate with remote IPv4-only nodes. However,
applications that rely upon IPv4 address literals instead of DNS
names will fail (unless 464XLAT [RFC6877] is used). An iterative
Yamamoto & Toyota Expires 11 March 2024 [Page 3]
Internet-Draft IPv6-only Resolver September 2023
resolver is a service that uses literal IP addresses, so it cannot
use the DNS64. This problem can be solved by the iterative resolver
converting IPv4 addresses to IPv6 addresses using the Pref64::/n
NAT64 prefix and following the address translation algorithm in
[RFC6052]. In doing so, an IPv6 packet conveying the query is
directed to a stateful NAT64 function that converts the IPv6 packet
to an IPv4 packet. With this implementation, an iterative resolver
can be operated even inside an IPv6-only network.
3.1. Deployment Scenarios and Examples
The deployment of IPv6-only networks is in progress, as demonstrated
by [draft-xie-v6ops-framework-md-ipv6only-underlay]. By operating an
IPv6-only network and limiting IPv4 reachability to NAT64 functions,
operators can optimize IPv4 address usage and concentrate on IPv6
operations, which is generally believed to lower operational costs
and optimize operations compared to a dual-stack environment.
In examples of past RFCs, name resolvers have always had an IPv4
address. For example, all three use cases for DNS64 in [RFC6147] are
dual-stack name servers.
+---------------------+ +---------------+
|IPv6 network | | IPv4 |
| +-------------+ | Internet |
| |--| Name server |--| |
| | | with DNS64 | | +----+ |
| +----+ | +-------------+ | | H2 | |
| | H1 |---| | | +----+ |
| +----+ | +------------+ | 192.0.2.1 |
| |---| IPv6/IPv4 |--| |
| | | Translator | | |
| | +------------+ | |
| | | | |
+---------------------+ +---------------+
Figure 1: Example network setup of the use of DNS64 described in
Section7.1 of RFC6147
Yamamoto & Toyota Expires 11 March 2024 [Page 4]
Internet-Draft IPv6-only Resolver September 2023
+---------------------+ +---------------+
|IPv6 network | | IPv4 |
| +--------+ | Internet |
| |-----| Name |----| |
| +-----+ | | server | | +----+ |
| | H1 | | +--------+ | | H2 | |
| |with |---| | | +----+ |
| |DNS64| | +------------+ | 192.0.2.1 |
| +----+ |---| IPv6/IPv4 |--| |
| | | Translator | | |
| | +------------+ | |
| | | | |
+---------------------+ +---------------+
Figure 2: Example network setup of the use of DNS64 described in
Section7.2 of RFC6147
However, it is necessary to consider the existence of an IPv6 single-
stack full-service resolver. In this document we consider an
IPv6-only network where the iterative resolver is inside the
IPv6-only network and does not have an IPv4 address. This is to
restrict IPv4 management to the NAT64 function.
+--------------------------+ +----------------------+
| IPv6 network | | IPv4 |
| | | Internet |
| | | | |
| +----------+ | | | +--------------+ |
| |IPv6-only | | | | |Authoritative | |
| |Iterative | | | | |server | |
| |resolver |---| +------------+ | +--------------+ |
| +----------+ |---| IPv6/IPv4 |--| 192.0.2.1 |
| | | Translator | | |
| +------------+ | |
| | | |
+--------------------------+ +----------------------+
Figure 3: Network example referenced in this document with an
IPv6-only iterative resolver
4. Solution with Existing Protocols
This section describes the mechanism of an IPv6-only capable resolver
utilising stateful NAT64. We assume that one or more IPv6/IPv4
translators [NAT64] are connecting an IPv6 network to an IPv4
network. The stateful NAT64 provides translation service and bridges
the two networks, allowing communication between IPv6-only hosts and
IPv4-only hosts. The IPv6-only capable resolver proposed in this
Yamamoto & Toyota Expires 11 March 2024 [Page 5]
Internet-Draft IPv6-only Resolver September 2023
document performs the IPv4 to IPv6 synthesis for the resolver to
communicate with IPv4-only servers via stateful NAT64. By using
stateful NAT64, this IPv6-only iterative resolver aligns with the
dual-stack requirements of BCP91 [RFC3901].
4.1. Finding an Authoritative Server with only IPv4 addresses
Before initiating a query, an iterative resolver may prioritize
authoritative servers with IPv6 addresses by sorting the SLIST data
structure, as described in [RFC1034]. If the resolver finds only an
A record for an authoritative server, the resolver should perform
address synthesis to the IPv4 address of the authoritative server,
converting IPv4 addresses to IPv6 by following the algorithm in
[RFC6052]. With this the IPv6 packet carrying the query is routed to
a stateful NAT64 function, which will convert the IPv6 packet with a
destination IPv4-converted IPv6 address that matches the NAT64 prefix
to an IPv4 packet. It is not recommended to synthesize IPv4
addresses of an authoritative server if it also has an IPv6 address.
4.2. Generating IPv4-converted IPv6 Addresses
4.2.1. Obtaining the Pref64::/n of a NAT64
The iterative resolver can obtain the Pref64::/n used by the
network's stateful NAT64 either by static configuration or by using a
discovery mechanism.
The Port Control Protocol [RFC7225] or Router Advertisements
[RFC8781] are two options available to the resolver if it wishes to
use a discovery mechanism to find the Pref64::/n. Using the
mechanisms described in [RFC7050] or [draft-hunek-v6ops-nat64-srv]
does not work because they require a resolver to work.
4.2.2. Performing Address Synthesis
The address translation algorithm is performed by following
Section 2.3 of [RFC6052]. After the synthesis is done, the IPv6-only
iterative resolver can send a query to the IPv4-converted IPv6
address.
5. Security Considerations
The use of NAT64 for address translation does not affect DNSSEC
operations as no part of the DNS message is altered.
Yamamoto & Toyota Expires 11 March 2024 [Page 6]
Internet-Draft IPv6-only Resolver September 2023
6. IANA Considerations
This document has no IANA actions.
7. Implementation Status
BIND has a work-in-progress branch available at:
https://gitlab.isc.org/isc-projects/bind9/-/merge_requests/6334/
commits
Unbound has an implementation in source, available from below PR:
https://github.com/NLnetLabs/unbound/pull/722
Building from source or using a version after Version 1.19 will allow
to use this function.
8. References
8.1. Normative References
[NAT64] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/rfc/rfc6146>.
[RFC3901] Durand, A. and J. Ihren, "DNS IPv6 Transport Operational
Guidelines", BCP 91, RFC 3901, DOI 10.17487/RFC3901,
September 2004, <https://www.rfc-editor.org/rfc/rfc3901>.
[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/rfc/rfc6052>.
8.2. Informative References
[draft-hunek-v6ops-nat64-srv]
Huněk, M., "NAT64/DNS64 detection via SRV Records", Work
in Progress, Internet-Draft, draft-hunek-v6ops-nat64-srv-
05, 15 June 2023, <https://datatracker.ietf.org/doc/html/
draft-hunek-v6ops-nat64-srv-05>.
[draft-xie-v6ops-framework-md-ipv6only-underlay]
Xie, C., Ma, C., Li, X., Mishra, G. S., Boucadair, M., and
T. Graf, "Framework of Multi-domain IPv6-only Underlay
Networks and IPv4 as a Service", Work in Progress,
Yamamoto & Toyota Expires 11 March 2024 [Page 7]
Internet-Draft IPv6-only Resolver September 2023
Internet-Draft, draft-xie-v6ops-framework-md-ipv6only-
underlay-05, 21 October 2022,
<https://datatracker.ietf.org/doc/html/draft-xie-v6ops-
framework-md-ipv6only-underlay-05>.
[ietf-v6ops-ipv6-deployment]
Fioccola, G., Volpato, P., Martinez, J. P., Mishra, G. S.,
and C. Xie, "IPv6 Deployment Status", Work in Progress,
Internet-Draft, draft-ietf-v6ops-ipv6-deployment-10, 1
December 2022, <https://datatracker.ietf.org/doc/html/
draft-ietf-v6ops-ipv6-deployment-10>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/rfc/rfc1034>.
[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/rfc/rfc6147>.
[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/rfc/rfc6877>.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis",
RFC 7050, DOI 10.17487/RFC7050, November 2013,
<https://www.rfc-editor.org/rfc/rfc7050>.
[RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
Port Control Protocol (PCP)", RFC 7225,
DOI 10.17487/RFC7225, May 2014,
<https://www.rfc-editor.org/rfc/rfc7225>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/rfc/rfc8499>.
[RFC8781] Colitti, L. and J. Linkova, "Discovering PREF64 in Router
Advertisements", RFC 8781, DOI 10.17487/RFC8781, April
2020, <https://www.rfc-editor.org/rfc/rfc8781>.
Yamamoto & Toyota Expires 11 March 2024 [Page 8]
Internet-Draft IPv6-only Resolver September 2023
Acknowledgments
TODO: acknowledge people.
Thank you for reading this draft.
Authors' Addresses
Momoka Yamamoto
The University of Tokyo/WIDE Project
Email: momoka.my6@gmail.com
Additional contact information:
山本 桃歌
The University of Tokyo/WIDE Project
Yasunobu Toyota
Keio University/WIDE Project
Email: yas-nyan@sfc.wide.ad.jp
Additional contact information:
豊田 安信
Keio University/WIDE Project
Yamamoto & Toyota Expires 11 March 2024 [Page 9]
