path: root/doc/rfc/rfc9527.txt

Internet Engineering Task Force (IETF)                        D. Migault
Request for Comments: 9527                                      Ericsson
Category: Standards Track                                       R. Weber
ISSN: 2070-1721                                                   Akamai
                                                            T. Mrugalski
                                                                     ISC
                                                            January 2024


            DHCPv6 Options for the Homenet Naming Authority

Abstract

   This document defines DHCPv6 options so that a Homenet Naming
   Authority (HNA) can automatically set the appropriate configuration
   and outsource the authoritative naming service for the home network.
   In most cases, the outsourcing mechanism is transparent for the end
   user.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9527.

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 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.  Terminology
   3.  Procedure Overview
   4.  DHCPv6 Options
     4.1.  Registered Homenet Domain Option
     4.2.  Forward Distribution Manager Option
     4.3.  Reverse Distribution Manager Server Option
     4.4.  Supported Transport
   5.  DHCPv6 Behavior
     5.1.  DHCPv6 Server Behavior
     5.2.  DHCPv6 Client Behavior
     5.3.  DHCPv6 Relay Agent Behavior
   6.  IANA Considerations
     6.1.  DHCPv6 Option Codes
     6.2.  Supported Transport Parameter
   7.  Security Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  Scenarios and Impact on the End User
     A.1.  Base Scenario
     A.2.  Third-Party Registered Homenet Domain
     A.3.  Third-Party DNS Infrastructure
     A.4.  Multiple ISPs
     Acknowledgments
     Contributors
   Authors' Addresses

1.  Introduction

   [RFC9526] specifies how an entity designated as the Homenet Naming
   Authority (HNA) outsources a Public Homenet Zone to a DNS Outsourcing
   Infrastructure (DOI).

   This document describes how a network can provision the HNA with a
   specific DOI.  This could be particularly useful for a DOI partly
   managed by an ISP or to make home networks resilient to HNA
   replacement.  The ISP delegates an IP prefix and the associated
   reverse zone to the home network.  The ISP is thus aware of the owner
   of that IP prefix and, as such, becomes a natural candidate for
   hosting the Homenet Reverse Zone -- that is, the Reverse Distribution
   Manager (RDM) and potentially the Reverse Public Authoritative
   Servers.

   In addition, ISPs often identify the line of the home network with a
   name.  Such name is used for their internal network management
   operations and is not a name the home network owner has registered
   to.  ISPs may leverage such infrastructure and provide the home
   network with a specific domain name designated per a Registered
   Homenet Domain [RFC9526].  Similarly to the reverse zone, ISPs are
   aware of who owns that domain name and may become a natural candidate
   for hosting the Homenet Zone -- that is, the Distribution Manager
   (DM) and the Public Authoritative Servers.

   This document describes DHCPv6 options that enable an ISP to provide
   the necessary parameters to the HNA to proceed.  More specifically,
   the ISP provides the Registered Homenet Domain and the necessary
   information on the DM and the RDM so the HNA can manage and upload
   the Public Homenet Zone and the Reverse Public Homenet Zone as
   described in [RFC9526].

   The use of DHCPv6 options may make the configuration completely
   transparent to the end user and provides a similar level of trust as
   the one used to provide the IP prefix, when provisioned via DHCP.

2.  Terminology

   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.

   The reader should be familiar with [RFC9526].

3.  Procedure Overview

   This section illustrates how an HNA receives the necessary
   information via DHCPv6 options to outsource its authoritative naming
   service to the DOI.  For the sake of simplicity, and similarly to
   [RFC9526], this section assumes that the HNA and the home network
   DHCPv6 client are colocated on the Customer Premises Equipment (CPE)
   router [RFC7368].  Also, note that this is not mandatory, and the
   DHCPv6 client may remotely instruct the HNA with a protocol that will
   be standardized in the future.  In addition, this section assumes
   that the responsible entity for the DHCPv6 server is provisioned with
   the DM and RDM information, which is associated with the requested
   Registered Homenet Domain.  This means a Registered Homenet Domain
   can be associated with the DHCPv6 client.

   This scenario is believed to be the most popular scenario.  This
   document does not ignore scenarios where the DHCPv6 server does not
   have privileged relations with the DM or RDM.  These cases are
   discussed in Appendix A.  Such scenarios do not necessarily require
   configuration for the end user and can also be zero configuration.

   The scenario considered in this section is as follows:

   1.  The HNA is willing to outsource the Public Homenet Zone or
       Homenet Reverse Zone.  The DHCPv6 client is configured to include
       in its Option Request Option (ORO) the Registered Homenet Domain
       Option (OPTION_REGISTERED_DOMAIN), the Forward Distribution
       Manager Option (OPTION_FORWARD_DIST_MANAGER), and the Reverse
       Distribution Manager Option (OPTION_REVERSE_DIST_MANAGER) option
       codes.

   2.  The DHCPv6 server responds to the DHCPv6 client with the
       requested DHCPv6 options based on the identified homenet.  The
       DHCPv6 client passes the information to the HNA.

   3.  The HNA is authenticated (see "Securing the Control Channel"
       (Section 6.6) of [RFC9526]) by the DM and the RDM.  The HNA
       builds the Homenet Zone (or the Homenet Reverse Zone) and
       proceeds as described in [RFC9526].  The DHCPv6 options provide
       the necessary non-optional parameters described in Appendix B of
       [RFC9526].  The HNA may complement the configurations with
       additional parameters via means not yet defined.  Appendix B of
       [RFC9526] describes such parameters that may take some specific
       non-default value.

4.  DHCPv6 Options

   This section details the payload of the DHCPv6 options following the
   guidelines of [RFC7227].

4.1.  Registered Homenet Domain Option

   The Registered Domain Option (OPTION_REGISTERED_DOMAIN) indicates the
   fully qualified domain name (FQDN) associated with the home network.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   OPTION_REGISTERED_DOMAIN    |         option-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                   Registered Homenet Domain                   /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Registered Domain Option

   option-code (16 bits):  OPTION_REGISTERED_DOMAIN; the option code for
      the Registered Homenet Domain (145).

   option-len (16 bits):  Length in octets of the Registered Homenet
      Domain field as described in [RFC8415].

   Registered Homenet Domain (variable):  The FQDN registered for the
      homenet encoded as described in Section 10 of [RFC8415].

4.2.  Forward Distribution Manager Option

   The Forward Distribution Manager Option (OPTION_FORWARD_DIST_MANAGER)
   provides the HNA with the FQDN of the DM as well as the transport
   protocols for the communication between the HNA and the DM.  As
   opposed to IP addresses, the FQDN requires a DNS resolution before
   establishing the communication between the HNA and the DM.  However,
   the use of an FQDN provides multiple advantages over IP addresses.
   Firstly, it makes the DHCPv6 option easier to parse and smaller,
   especially when IPv4 and IPv6 addresses are expected to be provided.
   Then, the FQDN can reasonably be seen as a more stable identifier
   than IP addresses as well as a pointer to additional information that
   may be useful, in the future, to establish the communication between
   the HNA and the DM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  OPTION_FORWARD_DIST_MANAGER  |          option-len           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Supported Transport       |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   /                  Distribution Manager FQDN                    /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: Forward Distribution Manager Option

   option-code (16 bits):  OPTION_FORWARD_DIST_MANAGER; the option code
      for the Forward Distribution Manager Option (146).

   option-len (16 bits):  Length in octets of the enclosed data as
      described in [RFC8415].

   Supported Transport (16 bits):  Defines the Supported Transport by
      the DM (see Section 4.4).  Each bit represents a supported
      transport, and a DM MAY indicate the support of multiple modes.
      The bit for DNS over mutually authenticated TLS (DomTLS) MUST be
      set.

   Distribution Manager FQDN (variable):  The FQDN of the DM encoded as
      described in Section 10 of [RFC8415].

   It is worth noting that the DHCPv6 option specifies the Supported
   Transport without specifying any explicit port.  Unless the HNA and
   the DM have agreed on using a specific port -- for example, by
   configuration, or any out-of-band mechanism -- the default port is
   used and must be specified.  The specification of such default port
   may be defined in the specification of the designated Supported
   Transport or in any other document.  In the case of DomTLS, the
   default port value is 853 per DNS over TLS [RFC7858] and DNS Zone
   Transfer over TLS [RFC9103].

   The need to associate the port value to each Supported Transport in
   the DHCPv6 option has been balanced with the difficulty of handling a
   list of tuples (transport, port) and the possibility of using a
   dedicated IP address for the DM in case the default port is already
   in use.

4.3.  Reverse Distribution Manager Server Option

   The Reverse Distribution Manager Option (OPTION_REVERSE_DIST_MANAGER)
   provides the HNA with the FQDN of the DM as well as the transport
   protocols for the communication between the HNA and the DM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OPTION_REVERSE_DIST_MANAGER   |          option-len           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Supported Transport       |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   /              Reverse Distribution Manager FQDN                /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 3: Reverse Distribution Manager Option

   option-code (16 bits):  OPTION_REVERSE_DIST_MANAGER; the option code
      for the Reverse Distribution Manager Option (147).

   option-len (16 bits):  Length in octets of the option-data field as
      described in [RFC8415].

   Supported Transport (16 bits):  Defines the Supported Transport by
      the RDM (see Section 4.4).  Each bit represents a supported
      transport, and an RDM MAY indicate the support of multiple modes.
      The bit for DomTLS [RFC7858] MUST be set.

   Reverse Distribution Manager FQDN (variable):  The FQDN of the RDM
      encoded as described in Section 10 of [RFC8415].

   For the port number associated to the Supported Transport, the same
   considerations as described in Section 4.2 apply.

4.4.  Supported Transport

   The Supported Transport field of the DHCPv6 option indicates the
   Supported Transport protocols.  Each bit represents a specific
   transport mechanism.  A bit set to 1 indicates the associated
   transport protocol is supported.  The corresponding bits are assigned
   as described in Table 2.

   DNS over mutually authenticated TLS (DomTLS):  Indicates the support
      of DNS over TLS [RFC7858] and DNS Zone Transfer over TLS [RFC9103]
      as described in [RFC9526].

   As an example, the Supported Transport field expressing support for
   DomTLS looks as follows and has a numeric value of 0x0001:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        must be zero         |1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.  DHCPv6 Behavior

5.1.  DHCPv6 Server Behavior

   Section 18.3 of [RFC8415] governs server operation regarding option
   assignment.  As a convenience to the reader, we mention here that the
   server will send option foo only if configured with specific values
   for foo and if the client requested it.  In particular, when
   configured, the DHCPv6 server sends the Registered Homenet Domain
   Option, Distribution Manager Option, and Reverse Distribution Manager
   Option when requested by the DHCPv6 client by including necessary
   option codes in its ORO.

5.2.  DHCPv6 Client Behavior

   The DHCPv6 client includes the Registered Homenet Domain Option,
   Distribution Manager Option, and Reverse Distribution Manager Option
   in an ORO as specified in Sections 18.2 and 21.7 of [RFC8415].

   Upon receiving a DHCPv6 option, as described in this document, in the
   Reply message, the HNA SHOULD proceed as described in [RFC9526].

5.3.  DHCPv6 Relay Agent Behavior

   There are no additional requirements for the DHCPv6 Relay agents.

6.  IANA Considerations

6.1.  DHCPv6 Option Codes

   IANA has assigned the following new DHCPv6 Option Codes in the
   "Option Codes" registry maintained at
   <https://www.iana.org/assignments/dhcpv6-parameters>.

   +=====+=============================+======+===========+===========+
   |Value| Description                 |Client| Singleton | Reference |
   |     |                             |ORO   | Option    |           |
   +=====+=============================+======+===========+===========+
   |145  | OPTION_REGISTERED_DOMAIN    |Yes   | No        | RFC 9527, |
   |     |                             |      |           | Section   |
   |     |                             |      |           | 4.1       |
   +-----+-----------------------------+------+-----------+-----------+
   |146  | OPTION_FORWARD_DIST_MANAGER |Yes   | Yes       | RFC 9527, |
   |     |                             |      |           | Section   |
   |     |                             |      |           | 4.2       |
   +-----+-----------------------------+------+-----------+-----------+
   |147  | OPTION_REVERSE_DIST_MANAGER |Yes   | Yes       | RFC 9527, |
   |     |                             |      |           | Section   |
   |     |                             |      |           | 4.3       |
   +-----+-----------------------------+------+-----------+-----------+

                      Table 1: Option Codes Registry

6.2.  Supported Transport Parameter

   IANA has created and maintains a new registry called "Supported
   Transport" under the "Dynamic Host Configuration Protocol for IPv6
   (DHCPv6)" registry at <https://www.iana.org/assignments/
   dhcpv6-parameters>.  This registry contains Supported Transport
   parameters in the Distributed Manager Option
   (OPTION_FORWARD_DIST_MANAGER) or the Reverse Distribution Manager
   Option (OPTION_REVERSE_DIST_MANAGER).  The different parameters are
   defined in Table 2 (Section 6.2).

   The Supported Transport field of the DHCPv6 option is a two-octet
   field that indicates the Supported Transport protocols.  Each bit
   represents a specific transport mechanism.

   New entries MUST specify the bit position, the transport protocol
   description, a mnemonic, and a reference as shown in Table 2.

   Changes to the format or policies of the registry are managed by the
   IETF via the IESG.

   Future code points are assigned under RFC Required per [RFC8126].
   The initial registry is as specified in Table 2 below.

   +======================+====================+==========+===========+
   | Bit Position (least  | Transport Protocol | Mnemonic | Reference |
   | to most significant) | Description        |          |           |
   +======================+====================+==========+===========+
   | 0                    | DNS over mutually  | DomTLS   | RFC 9527  |
   |                      | authenticated TLS  |          |           |
   +----------------------+--------------------+----------+-----------+
   | 1-15                 | Unassigned         |          |           |
   +----------------------+--------------------+----------+-----------+

                  Table 2: Supported Transport Registry

7.  Security Considerations

   The security considerations in [RFC8415] are to be considered.  The
   trust associated with the information carried by the DHCPv6 options
   described in this document is similar to the one associated with the
   IP prefix, when configured via DHCPv6.

   In some cases, the ISP MAY identify the HNA by its wire line (i.e.,
   physically), which may not require relying on TLS to authenticate the
   HNA.  As the use of TLS is mandatory, it is expected that the HNA
   will be provisioned with a certificate.  In some cases, the HNA may
   use a self-signed certificate.

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>.

   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <https://www.rfc-editor.org/info/rfc7858>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

   [RFC9103]  Toorop, W., Dickinson, S., Sahib, S., Aras, P., and A.
              Mankin, "DNS Zone Transfer over TLS", RFC 9103,
              DOI 10.17487/RFC9103, August 2021,
              <https://www.rfc-editor.org/info/rfc9103>.

   [RFC9526]  Migault, D., Weber, R., Richardson, M., and R. Hunter,
              "Simple Provisioning of Public Names for Residential
              Networks", RFC 9526, DOI 10.17487/RFC9526, January 2024,
              <https://www.rfc-editor.org/info/rfc9526>.

8.2.  Informative References

   [CNAME-PLUS-DNAME]
              Surý, O., "CNAME+DNAME Name Redirection", Work in
              Progress, Internet-Draft, draft-sury-dnsop-cname-plus-
              dname-01, 15 July 2018,
              <https://datatracker.ietf.org/doc/html/draft-sury-dnsop-
              cname-plus-dname-01>.

   [PD-REVERSE]
              Andrews, M., "Automated Delegation of IP6.ARPA reverse
              zones with Prefix Delegation", Work in Progress, Internet-
              Draft, draft-andrews-dnsop-pd-reverse-02, 5 November 2013,
              <https://datatracker.ietf.org/doc/html/draft-andrews-
              dnsop-pd-reverse-02>.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC6672]  Rose, S. and W. Wijngaards, "DNAME Redirection in the
              DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
              <https://www.rfc-editor.org/info/rfc6672>.

   [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
              <https://www.rfc-editor.org/info/rfc7227>.

   [RFC7368]  Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J.
              Weil, "IPv6 Home Networking Architecture Principles",
              RFC 7368, DOI 10.17487/RFC7368, October 2014,
              <https://www.rfc-editor.org/info/rfc7368>.

Appendix A.  Scenarios and Impact on the End User

   This appendix details various scenarios and discusses their impact on
   the end user.  This appendix is not normative and limits the
   description of a limited scope of scenarios that are assumed to be
   representative.  Many other scenarios may be derived from these.

A.1.  Base Scenario

   The base scenario, as described in Section 3, is one in which an ISP
   manages the DHCPv6 server, DM, and RDM.

   The end user subscribes to the ISP (foo), and at subscription time,
   it registers foo.example as its Registered Homenet Domain.

   In this scenario, the DHCPv6 server, DM, and RDM are managed by the
   ISP, so the DHCPv6 server and such can provide authentication
   credentials of the HNA to enable secure authenticated transaction
   with the DM and the Reverse DM.

   The main advantage of this scenario is that the naming architecture
   is configured automatically and transparently for the end user.  The
   drawbacks are that the end user uses a Registered Homenet Domain
   managed by the ISP and that it relies on the ISP naming
   infrastructure.

A.2.  Third-Party Registered Homenet Domain

   This appendix considers the case where the end user wants its home
   network to use example.com but does not want it to be managed by the
   ISP (foo) as a Registered Homenet Domain, and the ISP manages the
   home network and still provides foo.example as a Registered Homenet
   Domain.

   When the end user buys the domain name example.com, it may request to
   redirect example.com to foo.example using static redirection with
   CNAME [RFC1034] [RFC2181], DNAME [RFC6672], or CNAME+DNAME
   [CNAME-PLUS-DNAME].  The only information the end user needs to know
   is the domain name assigned by the ISP.  Once the redirection has
   been configured, the HNA may be changed, and the zone can be updated
   as described in Appendix A.1 without any additional configuration
   from the end user.

   The main advantage of this scenario is that the end user benefits
   from the zero configuration of the base scenario in Appendix A.1.
   Then, the end user is able to register an unlimited number of domain
   names provided by an unlimited number of different third-party
   providers for its home network.  The drawback of this scenario may be
   that the end user still needs to rely on the ISP naming
   infrastructure.  Note that this may be inconvenient in the case where
   the DNS servers provided by the ISPs result in high latency.

A.3.  Third-Party DNS Infrastructure

   This scenario involves the end user using example.com as a Registered
   Homenet Domain and not relying on the authoritative servers provided
   by the ISP.

   In this appendix, we limit the outsourcing of the DM and Public
   Authoritative Server(s) to a third party.  The Reverse Public
   Authoritative Server(s) and the RDM remain managed by the ISP as the
   IP prefix is managed by the ISP.

   Outsourcing to a third-party DM can be performed in the following
   ways:

   1.  Updating the DHCPv6 server information.  One can imagine a GUI
       interface that enables the end user to modify its profile
       parameters.  Again, this configuration update only needs to be
       performed one time.

   2.  Uploading the configuration of the DM to the HNA.  In some cases,
       the provider of the CPE router hosting the HNA may be the
       registrar, and the registrar may provide the CPE router already
       configured.  In other cases, the CPE router may request the end
       user to log into the registrar to validate the ownership of the
       Registered Homenet Domain and agree on the necessary credentials
       to secure the communication between the HNA and the DM.  As
       described in [RFC9526], such settings could be performed in an
       almost automatic way as to limit the necessary interactions with
       the end user.

A.4.  Multiple ISPs

   This scenario involves an HNA connected to multiple ISPs.

   Suppose the HNA has configured each of its interfaces independently
   with each ISP as described in Appendix A.1.  Each ISP provides a
   different Registered Homenet Domain.

   The protocol and DHCPv6 options described in this document are fully
   compatible with an HNA connected to multiple ISPs with multiple
   Registered Homenet Domains.  However, the HNA should be able to
   handle different Registered Homenet Domains.  This is an
   implementation issue, which is outside the scope of this document.

   If an HNA is not able to handle multiple Registered Homenet Domains,
   the HNA may remain connected to multiple ISPs with a single
   Registered Homenet Domain.  In this case, one entity is chosen to
   host the Registered Homenet Domain.  This entity may be an ISP or a
   third party.  Note that having multiple ISPs can be motivation for
   bandwidth aggregation or connectivity failover.  In the case of
   connectivity failover, the failover concerns the access network, and
   a failure of the access network may not impact the core network where
   the DM and Public Authoritative Primaries are hosted.  In that sense,
   choosing one of the ISPs even in a scenario of multiple ISPs may make
   sense.  However, for the sake of simplicity, this scenario assumes
   that a third party has been chosen to host the Registered Homenet
   Domain.  Configuration is performed as described in Appendices A.2
   and A.3.

   With the configuration described in Appendix A.2, the HNA is expected
   to be able to handle multiple Registered Homenet Domains as the
   third-party redirect to one of the ISP's servers.  With the
   configuration described in Appendix A.3, DNS zones are hosted and
   maintained by the third party.  A single DNS(SEC) Homenet Zone is
   built and maintained by the HNA.  This latter configuration is likely
   to match most HNA implementations.

   The protocol and DHCPv6 options described in this document are fully
   compatible with an HNA connected to multiple ISPs.  Whether to
   configure the HNA or not, and how to configure the HNA, depends on
   the HNA facilities.  Appendices A.1 and A.2 require the HNA to handle
   multiple Registered Homenet Domains, whereas Appendix A.3 does not
   have such a requirement.

Acknowledgments

   We would like to thank Marcin Siodelski, Bernie Volz, and Ted Lemon
   for their comments on the design of the DHCPv6 options.  We would
   also like to thank Mark Andrews, Andrew Sullivan, and Lorenzo Colliti
   for their remarks on the architecture design.  The designed solution
   has been largely inspired by Mark Andrews's document [PD-REVERSE] as
   well as discussions with Mark.  We also thank Ray Hunter and Michael
   Richardson for their reviews and comments and for suggesting
   appropriate terminology.

Contributors

   The coauthors would like to thank Chris Griffiths and Wouter Cloetens
   for providing significant contributions to the early draft versions
   of this document.

Authors' Addresses

   Daniel Migault
   Ericsson
   8275 Trans Canada Route
   Saint Laurent QC 4S 0B6
   Canada
   Email: daniel.migault@ericsson.com


   Ralf Weber
   Akamai
   Email: ralf.weber@akamai.com


   Tomek Mrugalski
   Internet Systems Consortium, Inc.
   PO Box 360
   Newmarket, NH 03857
   United States of America
   Email: tomasz.mrugalski@gmail.com