wdiff rfc9526v1.txt rfc9526.txt

Internet Engineering Task Force (IETF) D. Migault
Request for Comments: 9526 Ericsson
Category: Experimental R. Weber
ISSN: 2070-1721 Nominum
M. Richardson
Sandelman Software Works
R. Hunter
Globis Consulting BV
December 2023
January 2024

Simple Provisioning of Public Names for Residential Networks

Abstract

Home network owners may have devices or services hosted on their home
network that they wish to access from the Internet (i.e., from a
network outside of the home network). Home networks are increasingly
numbered using IPv6 addresses, which in principle makes this access
simpler, but accessing home networks from the Internet requires the
names and IP addresses of these devices and services to be made
available in the public DNS.

This document describes how a Home Naming Authority (NHA) instructs
the outsourced infrastructure to publish these pieces of information
in the public DNS. The names and IP addresses of the home network
are set in the Public Homenet Zone by the Homenet Naming Authority
(HNA), which in turn instructs an outsourced infrastructure to
publish the zone on behalf of the home network owner.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.

This document defines an Experimental Protocol for the Internet
community. 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). Not
all documents approved by the IESG are candidates for any level of
Internet Standard; see 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/rfc9526.

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. Selecting Names and Addresses to Publish
4. Envisioned Deployment Scenarios
4.1. CPE Vendor
4.2. Agnostic CPE
5. Architecture Description
5.1. Architecture Overview
5.2. Distribution Manager (DM) Communication Channels
6. Control Channel
6.1. Information to Build Building the Public Homenet Zone
6.2. Information to Build Building the DNSSEC Chain of Trust
6.3. Information to Set Setting Up the Synchronization Channel
6.4. Deleting the Delegation
6.5. Messages Message Exchange Description
6.5.1. Retrieving Information for the Public Homenet Zone
6.5.2. Providing Information for the DNSSEC Chain of Trust
6.5.3. Providing Information for the Synchronization Channel
6.5.4. HNA Instructing Deleting Initiating Deletion of the Delegation
6.6. Securing the Control Channel
7. Synchronization Channel
7.1. Securing the Synchronization Channel
8. DM Distribution Channel
9. HNA Security Policies
10. Public Homenet Reverse Zone
11. DNSSEC-Compliant Homenet Architecture
12. Renumbering
13. Privacy Considerations
14. Security Considerations
14.1. Registered Homenet Domain
14.2. HNA DM Channels
14.3. Names Are Less Secure than IP Addresses
14.4. Names Are Less Volatile than IP Addresses
14.5. Deployment Considerations
14.6. Operational Considerations
15. IANA Considerations
16. References
16.1. Normative References
16.2. Informative References
Appendix A. HNA Channel Configurations
A.1. Homenet Public Homenet Zone
Appendix B. Information Model for Outsourced Information
Appendix C. Example: A Manufacturer-Provisioned HNA Product Flow
Acknowledgments
Contributors
Authors' Addresses

1. Introduction

Home network owners may have devices or services hosted on their home
network that they wish to access from the Internet (i.e., from a
network outside of the home network). The use of IPv6 addresses in
the home makes, in principle, the actual network access simpler,
while on the other hand, the addresses are much harder to remember
and are subject to regular renumbering. To make this situation
simpler for typical home owners to manage, there needs to be an easy
way for the names and IP addresses of these devices and services to
be published in the public DNS.

As depicted in Figure 1, the names and IP address of the home network
are made available in the Public Homenet Zone by the Homenet Naming
Authority (HNA), which in turn instructs the DNS Outsourcing
Infrastructure (DOI) to publish the zone on behalf of the HNA. This
document describes how an HNA can instruct a DOI to publish a Public
Homenet Zone on its behalf.

This document introduces the Synchronization Channel and the Control
Channel between the HNA and the Distribution Manager (DM), which is
the main interface to the DOI.

The Synchronization Channel (see Section 7) is used to synchronize
the Public Homenet Zone.

Internet
.---------------------. .-------------------.
| Home Network | Control | DOI |
|.-------------------.| Channel |.-----------------.|
|| HNA |<----------->| Distribution ||
||.-----------------.|| || Manager ||
||| Public Homenet ||| || ||
||| Zone ||<----------->| ||
||| myhome.example ||| Synchron- |'-----------------'|
||'-----------------'|| ization | | |
|'-------------------'| Channel | V |
| | |.-----------------.|
| | || Public Homenet ||
'---------------------' || Zone ||
|| myhome.example ||
|'-----------------'|
'---^--^--^--^--^---'
| | | | |
(served on the Internet)

Figure 1: High-Level Architecture Overview of Outsourcing the
Public Homenet Zone

The Synchronization Channel is a zone transfer, with the HNA
configured as a primary server and the Distribution Manager
configured as a
secondary. secondary server. Some operators refer to this kind
of configuration as a "hidden primary", but that term is not used in
this document as it is not precisely defined anywhere, but it has
many slightly different meanings to many.

The Control Channel (see Section 6) is used to set up the
Synchronization Channel. This channel is in the form of a dynamic
DNS update process, authenticated by TLS.

For example, to build the Public Homenet Zone, the HNA needs the
authoritative servers (and associated IP addresses) of the DOI's
servers (the visible primaries) that are actually serving the zone.
Similarly, the DOI needs to know the IP address of the (hidden)
primary (HNA) as well as potentially the hash of the Key Signing Key
(KSK) in the DS RRset to secure the DNSSEC delegation with the parent
zone.

The remainder of the document is as follows.

Section 2 defines the terminology. Section 3 presents the general
problem of publishing names and IP addresses. Section 4 briefly
describes some potential envisioned deployment scenarios. And
Section 5 provides an architectural view of the HNA, DM, and DOI as
well as their different communication channels (Control Channel,
Synchronization Channel, and DM Distribution Channel) described in
Sections 6, 7, and 8, respectively.

Then, Sections 6 and 7 deal with the two channels that interface to
the home. Section 8 provides a set of requirements and expectations
on how the distribution system works. This section is non-normative
and not subject to standardization but reflects how many scalable DNS
distribution systems operate.

Sections 9 and 11 respectively detail HNA security policies as well
as DNSSEC compliance within the home network.

Section 12 discusses how renumbering should be handled.

Finally, Sections 13 and 14 respectively discuss privacy and security
considerations when outsourcing the Public Homenet Zone.

The appendices discuss the following aspects: management (see
Section 10), provisioning (see Section 10), configurations (see
Appendix B), and deployment (see Section 4 and Appendix C).

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.

Customer Premises Equipment (CPE): A router providing connectivity
to the home network.

Homenet Zone: The DNS zone for use within the boundaries of the home
network: "home.arpa" (see [RFC8375]). This zone is not considered
public and is out of scope for this document.

Registered Homenet Domain: The domain name that is associated with
the home network. A given home network may have multiple
Registered Homenet Domains.

Public Homenet Zone: Contains the names in the home network that are
expected to be publicly resolvable on the Internet. A home
network can have multiple Public Homenet Zones.

Homenet Naming Authority (HNA): A function responsible for managing
the Public Homenet Zone. This includes populating the Public
Homenet Zone, signing the zone for DNSSEC, as well as managing the
distribution of that Homenet Zone to the DOI.

DNS Outsourcing Infrastructure (DOI): The infrastructure responsible
for receiving the Public Homenet Zone and publishing it on the
Internet. It is mainly composed of a Distribution Manager and
Public Authoritative Servers.

Public Authoritative Servers: The authoritative name servers for the
Public Homenet Zone. Name resolution requests for the Registered
Homenet Domain are sent to these servers. Some DNS operators
refer to these as public secondaries, and higher resiliency
networks are often implemented in an anycast fashion.

Homenet Authoritative Servers: The authoritative name servers for
the Homenet Zone within the Homenet network itself. These are
sometimes called "hidden primary servers".

Distribution Manager (DM): The (set of) server(s) to which server (or set of servers) that the
HNA synchronizes the Public Homenet Zone, Zone to and which that then
distributes the relevant information to the Public Authoritative
Servers. This server has been historically known as the
Distribution Master.

Public Homenet Reverse Zone: The reverse zone file associated with
the Public Homenet Zone.

Reverse Public Authoritative Servers: These are equivalent to Public
Authoritative Servers, specifically for reverse resolution.

Reverse Distribution Manager: This is equivalent to the Distribution
Manager, specifically for reverse resolution.

Homenet DNS(SEC)

DNS Resolver: A resolver that performs a DNS(SEC) DNS resolution on the home network
Internet for the Public Homenet Zone. The resolution is performed
by requesting the Homenet Public Authoritative Servers.

DNS(SEC) While the
resolver does not necessarily perform DNSSEC resolutions, it is
RECOMMENDED that DNSSEC is enabled.

Note that when "DNS Resolver" is used in this document, it refers
to "DNS or DNSSEC Resolver".

Homenet DNS Resolver: A resolver that performs a DNS or DNSSEC
resolution on the
Internet home network for the Public Homenet Zone. The
resolution is performed by requesting the Public Homenet Authoritative
Servers.

3. Selecting Names and Addresses to Publish

While this document does not create any normative mechanism to select
the names to publish, it does anticipate that the home network
administrator (a human being) will be presented with a list of
current names and addresses either directly on the HNA or via another
device such as a smartphone.

The administrator will mark which devices and services (by name) are
to be published. The HNA will then collect the IP address(es)
associated with that device or service and put the name into the
Public Homenet Zone. The address of the device or service can be
collected from a number of places: Multicast DNS (mDNS) [RFC6762],
DHCP [RFC8415], Universal Plug and Play (UPnP), the Port Control
Protocol (PCP) [RFC6887], or manual configuration.

A device or service SHOULD have Global Unicast Addresses (GUAs) (IPv6
[RFC3787]
[RFC3587] or IPv4) but MAY also have IPv6 Unique Local Addresses
(ULAs) [RFC4193], IPv6 Link-Local Addresses (LLAs) [RFC4291]
[RFC7404], IPv4 LLAs [RFC3927], and private IPv4 addresses [RFC1918].

Of these, the LLAs are almost never useful for the Public Zone and
should be omitted.

The IPv6 ULA and private IPv4 addresses may be useful to publish, if
the home network environment features a VPN that would allow the home
owner to reach the network. [RFC1918] addresses in public zones are
generally filtered out by many DNS servers as they are considered
rebind attacks [REBIND].

In general, one expects the GUA to be the default address to be
published. A direct advantage of enabling local communication is to
enable communications even in case of Internet disruption. Since
communications are established with names that remain a global
identifier, the communication can be protected (at the very least
with integrity protection) by TLS the same way it is protected on the
global Internet -- by using certificates.

4. Envisioned Deployment Scenarios

A number of deployment scenarios have been envisioned; this section
aims at providing a brief description. The use cases are not
limitations, and this section is not normative.

The main difference between the various deployments concerns the
provisioning of the HNA -- that is, how it is configured to outsource
the Public Homenet Zone to the DOI -- as well as how the Public
Homenet Zone is being provisioned before being outsourced. In both
cases, these configuration aspects are out of the scope of this
document.

Provisioning the configuration related to the DOI is expected to be
automated as much as possible and require interaction with the end
user as little as possible. Zero configuration can only be achieved
under some circumstances, and [RFC9527] provides one such example
under the assumption that the ISP provides the DOI. Section 4.1
describes another variant where the Customer Premises Equipment (CPE)
is provided preconfigured with the DOI. Section 4.2 describes how an
agnostic CPE may be configured by the home network administrator. Of
course even in this case, the configuration can leverage mechanisms
to prevent the end user from manually entering all information.

On the other hand, provisioning the Public Homenet Zone needs to
combine the ability to closely reflect what the end user wishes to
publish on the Internet while easing such interaction. The HNA may
implement such interactions using Web GUI web-based GUIs or specific mobile
applications.

With the CPE configured with the DOI, the HNA contacts the DOI to
build a template for the Public Homenet Zone and then provisions the
Public Homenet Zone. Once the Public Homenet Zone is built, the HNA
starts synchronizing it with the DOI on the Synchronization Channel.

4.1. CPE Vendor

A specific vendor that has specific relations with a registrar or a
registry may sell a CPE that is provisioned with a domain name. Such
a domain name is probably not human friendly and may consist of some
kind of serial number associated with the device being sold.

One possible scenario is that the vendor provisions the HNA with a
private key with an associated certificate used for the mutual TLS
authentication. Note that these keys are not expected to be used for
DNSSEC signing.

Instead, these keys are solely used by the HNA for the authentication
to the DM. Normally, the keys should be are necessary and sufficient to
proceed to the authentication.

When the home network owner plugs in the CPE at home, the relation
between the HNA and DM is expected to work out of the box.

4.2. Agnostic CPE

A CPE that is not preconfigured may also use the protocol defined in
this document, but some configuration steps will be needed.

1. The owner of the home network buys a domain name from a registrar
and, as such, creates an account on that registrar.

2. The registrar may provide the outsourcing infrastructure, or the
home network may need to create a specific account on the
outsourcing infrastructure.

* If the DOI is the DNS Registrar, it has by design a proof of
ownership of the domain name by the Homenet owner. In this case,
it is expected that the DOI provides the necessary parameters to
the home network owner to configure the HNA. One potential
mechanism to provide the parameters would be to provide the user
with a JSON object that they can copy and paste into the CPE, such
as described in Appendix B. But what matters to the
infrastructure is that the HNA is able to authenticate itself to
the DOI.

* If the DOI is not the DNS Registrar, then the proof of ownership
needs to be established using some other protocol. Automatic
Certificate Management Environment (ACME) [RFC8555] is one
protocol that would allow an owner of an existing domain name to
prove their ownership (but it requires that they have DNS already
set up!). There are other ways to establish proof such as putting
providing a DOI-generated TXT record, or web site contents, as
championed by entities like Google's Sitemaster and Postmaster
protocols. [DOMAIN-VALIDATION] describes a few ways ownership or
control of a domain can be achieved.

5. Architecture Description

This section provides an overview of the architecture for outsourcing
the authoritative naming service from the HNA to the DOI. As a
consequence, this prevents HNA from handling the DNS traffic from the
Internet that is associated with the resolution of the Homenet Zone.

The device-assigned zone or user-configurable zone that is used as
the domain to publicly serve hostnames in the home network is called
the Public Homenet Zone. In this document, "myhome.example" is used
as the example for an end-user-owned domain configured as a Public
Homenet Zone.

More specifically, DNS resolution for the Public Homenet Zone (here
"myhome.example") from Internet DNSSEC resolvers is handled by the
DOI as opposed to the HNA. The DOI benefits from a cloud
infrastructure while the HNA is dimensioned for a home network and,
as such, is likely unable to support any load. In the case where the
HNA is a CPE, outsourcing to the DOI reduces the attack surface of
the home network to DDoS, for example. Of course, the DOI needs to
be informed dynamically about the content of myhome.example. The
description of such a synchronization mechanism is the purpose of
this document.

Note that Appendix B shows the necessary parameters to configure the
HNA.

5.1. Architecture Overview

.----------------------------. .-----------------------------.
| Home Network | | Internet |
| .-----------------------. | Control | .-----------------------. |
| | HNA | | Channel | | DOI | |
| | (hidden primary) |<------------->| (hidden secondary) | |
| | | | DNSUPD | | Distribution Manager | |
| | .-------------------. | | | | | |
| | | Public Homenet | | | | | .-------------------.| |
| | | Zone |<------------------>|Public Homenet Zone|| |
| | | myhome.example | | |Synchron-| | | myhome.example || |
| | '-------------------' | |ization | | '-------------------'| |
| '-----------------------' |Channel | | | | |
| ^ | AXFR | | | | |
| | | | | v | |
| .-----------------------. | | |.---------------------.| |
| | Homenet Authoritative | | | || Public Authoritative|| |
| | Server | | | || (secondary) Servers || |
| | + myhome.example | | | || + myhome.example || |
| | + home.arpa | | | || + x.y.z.ip6.arpa || |
| | + x.y.z.ip6.arpa | | | || || |
| '-----------------------' | | || || |
| | ^ | | |'---------------------'| |
| | | | | | ^ | | |
| | | | | '--|------------|-------' |
| v | | | | v |
| .----------------------. | | .------------------------. |
| | Homenet DNS Resolver | | | | Internet Resolvers | |
| '----------------------' | | '------------------------' |
| | | |
'----------------------------' | |
'-----------------------------'

Figure 2: Homenet Naming Architecture

Figure 2 illustrates the architecture where the HNA outsources the
publication of the Public Homenet Zone to the DOI. The DOI will
serve every DNS request of the Public Homenet Zone coming from
outside the home network. When the request is coming from within the
home network, the resolution is expected to be handled by the Homenet
DNS Resolver as further detailed below.

In this example, the Public Homenet Zone is identified by the
Registered Homenet Domain name "myhome.example". This diagram also
shows a reverse IPv6 map being hosted.

The

".local" as well as and ".home.arpa" are explicitly not considered Public
Homenet Zones and Zones; therefore, they are represented as a Homenet Zone in
Figure 2. They are resolved locally but are not published because
they are considered local content.

It is RECOMMENDED that the HNA implements DNSSEC, in which case the
HNA MUST sign the Public Homenet Zone with DNSSEC.

The HNA handles all operations and keying material required for
DNSSEC, so there is no provision made in this architecture for
transferring private DNSSEC-related keying material between the HNA
and the DM.

Once the Public Homenet Zone has been built, the HNA communicates and
synchronizes it with the DOI using a primary/secondary setting as
depicted in Figure 2. The HNA acts as a stealth server (see
[RFC8499]) while the DM behaves as a hidden secondary. It is
responsible for distributing the Public Homenet Zone to the multiple
Public Authoritative Server instances that DOI is responsible for.
The DM has three communication channels:

* DM Control Channel (Section 6) to configure the HNA and the DOI.
This includes necessary parameters to configure the primary/
secondary relation as well as some information provided by the DOI
that needs to be included by the HNA in the Public Homenet Zone.

* DM Synchronization Channel (Section 7) to synchronize the Public
Homenet Zone on the HNA and on the DM with the appropriately
configured primary/secondary. This is a zone transfer over
mutually authenticated TLS.

* One or more Distribution Channels (Section 8) that distribute the
Public Homenet Zone from the DM to the Public Authoritative
Servers serving the Public Homenet Zone on the Internet.

There might be multiple DMs and multiple servers per the DM. This
document assumes a single DM server for simplicity, but there is no
reason why each channel needs to be implemented on the same server or
use the same code base.

It is important to note that while the HNA is configured as an
authoritative server, it is not expected to answer DNS requests from
the _public_ Internet for the Public Homenet Zone. More
specifically, the addresses associated with the HNA SHOULD NOT be
mentioned in the NS records of the Public Homenet Zone, unless
additional security provisions necessary to protect the HNA from
external attack have been taken.

The DOI is also responsible for ensuring the DS record has been
updated in the parent zone.

Resolution is performed by DNS(SEC) resolvers. DNS Resolvers. When the resolution is
performed outside the home network, the DNS(SEC) DNS Resolver resolves the DS
record on the Global DNS and the name associated with the Public
Homenet Zone (myhome.example) on the Public Authoritative Servers.

In order to provide resilience to the Public Homenet Zone in case of
WAN connectivity disruption, the Homenet DNS(SEC) DNS Resolver MUST be able to
perform the resolution on the Homenet Authoritative Servers. Note
that the use of the Homenet resolver DNS Resolver enhances privacy since the
user on the home network would no longer be leaking interactions with
internal services to an external DNS provider and to an on-path
observer. These servers are not expected to be mentioned in the
Public Homenet Zone nor to be accessible from the Internet. As such,
their information as well as the corresponding signed DS record MAY
be provided by the HNA to the Homenet DNS(SEC) DNS Resolvers, e.g., by using
the Home Networking Control Protocol (HNCP) [RFC7788] or by
configuring a trust anchor [DRO-RECS]. Such configuration is outside
the scope of this document. Since the scope of the Homenet
Authoritative Servers is limited to the home network, these servers
are expected to serve the Homenet Zone as represented in Figure 2.

5.2. Distribution Manager (DM) Communication Channels

This section details the DM channels: the Control Channel,
Synchronization Channel, and Distribution Channel.

The Control Channel and the Synchronization Channel are the
interfaces used between the HNA and the DOI. The entity within the
DOI responsible for handling these communications is the DM.
Communications between the HNA and the DM MUST be protected and
mutually authenticated. The different protocols that can be used for
security are discussed in more depth in Section 6.6.

The information exchanged between the HNA and the DM uses DNS
messages protected by DNS over TLS (DoT) [RFC7858]. This is
configured identically to that described in [RFC9103], Section 9.3.3.

It is worth noting that both the DM and HNA need to agree on a common
configuration in order to set up the Synchronization Channel as well as to and
build and server serve a coherent Public Homenet Zone. As previously noted,
the visible NS records of the Public Homenet Zone (built by the HNA)
remain pointing at the IP address of the DOI's Public Authoritative
Servers. Unless the HNA is able to support the traffic load, the HNA
SHOULD NOT appear as a visible NS record of the Public Homenet Zone.
In addition, and depending on the configuration of the DOI, the DM
also needs to update the parent zone's NS, DS, and associated A or
AAAA glue records. Refer to Section 6.2 for more details.

This specification assumes:

* The DM serves both the Control Channel and Synchronization Channel
on a single IP address, on a single port port, and by using a single
transport protocol.

* By default, the HNA uses a single IP address for both the Control
and Synchronization channels; however, the HNA MAY use distinct IP
addresses for the Control Channel and the Synchronization Channel
-- see Sections 7 and 6.3 for more details.

The Distribution Channel is internal to the DOI and, as such, is not
normatively defined by this specification.

6. Control Channel

The DM Control Channel is used by the HNA and the DOI to exchange
information related to the configuration of the delegation, which
includes information to build the Public Homenet Zone (Section 6.1),
to build the DNSSEC chain of trust (Section 6.2), and to set the
Synchronization Channel (Section 6.3).

Some information is carried from the DOI to the HNA, as described in
the next section. The HNA updates the DOI with the IP address on
which the zone is to be transferred using the Synchronization
Channel. The HNA is always initiating the exchange in both
directions.

As such, the HNA has a prior knowledge of the DM identity (via an
X.509 certificate), the IP address and port number to use, and the
protocol to establish a secure session. The DM acquires knowledge of
the identity of the HNA (X.509 certificate) as well as the Registered
Homenet Domain. For more detail on how this can be achieved, please
see Appendix A.1.

6.1. Information to Build Building the Public Homenet Zone

The HNA builds the Public Homenet Zone based on a template that is
returned by the DM to the HNA. Section 6.5 explains how this
leverages the Authoritative Transfer (AXFR) mechanism.

In order to build its zone completely, the HNA needs the names (and
possibly IP addresses) of the Public Authoritative Name Servers.
These are used to populate the NS records for the zone. All the
content of the zone MUST be created by the HNA because the zone is
DNSSEC signed.

In addition, the HNA needs to know what to put into the MNAME of the
SOA, and only the DOI knows what to put there. The DM MUST also
provide useful operational parameters such as other fields of the SOA
(SERIAL, RNAME, REFRESH, RETRY, EXPIRE, and MINIMUM); however, the
HNA is free to override these values based upon local configuration.
For instance, an HNA might want to change these values if it thinks
that a renumbering event is approaching.

Because the information associated with the DM is necessary for the
HNA to proceed, this information exchange is mandatory.

The HNA then performs a DNS Update operation to the DOI, updating the
DOI with an NS, a DS, and A and AAAA records. These indicate where
its Synchronization Channel is. The DOI does not publish this NS
record but uses it to perform zone transfers.

6.2. Information to Build Building the DNSSEC Chain of Trust

The HNA MUST provide the hash of the KSK via the DS RRset so that the
DOI can provide this value to the parent zone. A common deployment
use case is that the DOI is the registrar of the Registered Homenet
Domain; therefore, its relationship with the registry of the parent
zone enables it to update the parent zone. When such relation
exists, the HNA should be able to request the DOI to update the DS
RRset in the parent zone. A direct update is especially necessary to
initialize the chain of trust.

Though the HNA may also directly update the values of the DS via the
Control Channel at a later time, it is RECOMMENDED to use other
mechanisms such as CDS and CDNSKEY [RFC7344] for transparent updates
during key rollovers.

As some deployments may not provide a DOI that will be able to update
the DS in the parent zone, this information exchange is OPTIONAL.

By accepting the DS RR, the DM commits to advertise the DS to the
parent zone. On the other hand, if the DM does not have the capacity
to advertise the DS to the parent zone, it indicates this by refusing
the update to the DS RR.

6.3. Information to Set Setting Up the Synchronization Channel

The HNA works as a hidden primary authoritative DNS server while the
DM works like a secondary one. As a result, the HNA needs to provide
the IP address that the DM should use to reach the HNA.

If the HNA detects that it has been renumbered, then it MUST use the
Control Channel to update the DOI with the new IPv6 address it has
been assigned.

The Synchronization Channel will be set between the new IPv6 (and
IPv4) address and the IP address of the DM. By default, the IP
address used by the HNA in the Control Channel is considered by the
DM, and the explicit specification of the IP by the HNA is only
OPTIONAL. The transport channel (including the port number) is the
same as the one used between the HNA and the DM for the Control
Channel.

6.4. Deleting the Delegation

The purpose of the previous sections is to exchange information in
order to set a delegation. The HNA MUST also be able to delete a
delegation with a specific DM.

Section 6.5.4 explains how a DNS Update operation on the Control
Channel is used.

Upon receiving the instruction to delete the delegation, the DM MUST
stop serving the Public Homenet Zone.

The decision to delete an inactive HNA by the DM is part of the
commercial agreement between the DOI and HNA.

6.5. Messages Message Exchange Description

Multiple ways were considered on how the control information could be
exchanged between the HNA and the DM.

This specification defines a mechanism that reuses the DNS zone
transfer format. Note that while information is provided using DNS
exchanges, the exchanged information is not expected to be set in any
zone file; instead, this information is used as commands between the
HNA and the DM. This was found to be simpler on the home router
side, as the HNA already has to have code to deal with all the DNS
encodings/decodings. Inventing a new way to encode the DNS
information in, for instance, JSON seemed to add complexity for no
return on investment.

The Control Channel is not expected to be a long-term session. After
a predefined timer (similar to those used for TCP), the Control
Channel is expected to be terminated by closing the transport
channel. The Control Channel MAY be reopened at any later time.

The use of TLS session tickets (see [RFC8446], Section 4.6.1) is
RECOMMENDED.

The authentication of the channel MUST be based on certificates for
both the DM and each HNA. The DM may also create the initial
configuration for the delegation zone in the parent zone during the
provisioning process.

6.5.1. Retrieving Information for the Public Homenet Zone

The information provided by the DM to the HNA is retrieved by the HNA
with an AXFR exchange [RFC1034]. AXFR enables the response to
contain any type of RRsets.

To retrieve the necessary information to build the Public Homenet
Zone, the HNA MUST send a DNS request of type AXFR associated with
the Registered Homenet Domain.

The zone that is returned by the DM is used by the HNA as a template
to build its own zone.

The zone template MUST contain an RRset of type SOA, one or multiple
RRsets of type NS, and zero or more RRsets of type A or AAAA (if the
NS is in-domain [RFC8499]). The zone template will include Time-To-
Live (TTL) values for each RR, and the HNA SHOULD take these as
suggested maximum values, but it MAY use lower values for operational
reasons, such as for impending renumbering events.

* The SOA RR indicates the value of the MNAME of the Public Homenet
Zone to the HNA.

* The NAME of the SOA RR MUST be the Registered Homenet Domain.

* The MNAME value of the SOA RDATA is the value provided by the DOI
to the HNA.

* Other RDATA values (RNAME, REFRESH, RETRY, EXPIRE, and MINIMUM)
are provided by the DOI as suggestions.

The NS RRsets carry the Public Authoritative Servers of the DOI.
Their associated NAME MUST be the Registered Homenet Domain.

In addition to the considerations above about default TTL, the HNA
SHOULD take care to not pick a TTL larger than the parent NS, based
upon the resolver's guidelines in [NS-REVALIDATION] and [DRO-RECS].
The RRsets of Type A and AAAA MUST have their NAME matching the
NSDNAME of one of the NS RRsets.

Upon receiving the response, the HNA MUST validate the format and
properties of the SOA, NS, and A or AAAA RRsets. If an error occurs,
the HNA MUST stop proceeding and MUST log an error. Otherwise, the
HNA builds the Public Homenet Zone by setting the MNAME value of the
SOA as indicated by the SOA provided by the AXFR response. The HNA
MUST not NOT exceed the values of NAME, REFRESH, RETRY, EXPIRE, and
MINIMUM of the SOA to those provided by the AXFR response. The HNA MUST
insert the NS and corresponding A or AAAA RRsets in its Public
Homenet Zone. The HNA MUST ignore other RRsets.

If an error message is returned by the DM, the HNA MUST proceed as a
regular DNS resolution. Error messages SHOULD be logged for further
analysis. If the resolution does not succeed, the outsourcing
operation is aborted and the HNA MUST close the Control Channel.

6.5.2. Providing Information for the DNSSEC Chain of Trust

To provide the DS RRset to initialize the DNSSEC chain of trust, the
HNA MAY send a DNS update [RFC3007] message.

The DNS update message is composed of a Header section, a Zone
section, a Prerequisite section, an Update section, and an additional
section. The Zone section MUST set the ZNAME to the parent zone of
the Registered Homenet Domain, which is where the DS records should
be inserted. As described in [RFC2136], ZTYPE is set to SOA and
ZCLASS is set to the zone's class. The Prerequisite section MUST be
empty. The Update section is a DS RRset with its NAME set to the
Registered Homenet Domain, and the associated RDATA corresponds to
the value of the DS. The Additional Data section MUST be empty.

Though the Prerequisite section MAY be ignored by the DM, this value
is fixed to remain coherent with a standard DNS update.

Upon receiving the DNS update request, the DM reads the DS RRset in
the Update section. The DM checks that ZNAME corresponds to the
parent zone. The DM MUST ignore the Prerequisite and Additional Data
sections, if present. The DM MAY update the TTL value before
updating the DS RRset in the parent zone. Upon a successful update,
the DM should return a NOERROR response as a commitment to update the
parent zone with the provided DS. An error indicates that the DM
does not update the DS, and the HNA needs to act accordingly;
otherwise, another method should be used by the HNA.

The regular DNS error message MUST be returned to the HNA when an
error occurs. In particular, a FORMERR is returned when a format
error is found, including when unexpected RRsets are added or when
RRsets are missing. A SERVFAIL error is returned when an internal
error is encountered. A NOTZONE error is returned when the Update
and Zone sections are not coherent, and a NOTAUTH error is returned
when the DM is not authoritative for the Zone section. A REFUSED
error is returned when the DM refuses to proceed to the configuration
and or performing
the requested action.

6.5.3. Providing Information for the Synchronization Channel

The default IP address used by the HNA for the Synchronization
Channel is the IP address of the Control Channel. To provide a
different IP address, the HNA MAY send a DNS UPDATE message.

Similar to what is described in Section 6.5.2, the HNA MAY specify
the IP address using a DNS update message. The Zone section sets its
ZNAME to the parent zone of the Registered Homenet Domain, ZTYPE to
SOA, and ZCLASS to the zone's type. Prerequisite is empty. The
Update section is an RRset of type NS. The Additional Data section
contains the RRsets of type A or AAAA that designate the IP addresses
associated with the primary (or the HNA).

The reason to provide these IP addresses is to keep them unpublished
and prevent them from being resolved. It is RECOMMENDED that the IP
address of the HNA be randomly chosen to prevent it from being easily
discovered as well.

Upon receiving the DNS update request, the DM reads the IP addresses
and checks that the ZNAME corresponds to the parent zone. The DM
MUST ignore a non-empty Prerequisite section. The DM configures the
secondary with the IP addresses and returns a NOERROR response to
indicate it is committed to serve as a secondary.

Similar to what is described in Section 6.5.2, DNS errors are used,
and an error indicates the DM is not configured as a secondary.

6.5.4. HNA Instructing Deleting Initiating Deletion of the Delegation

To initiate the deletion of the delegation, the HNA sends a DNS
UPDATE Delete message.

The Zone section sets its ZNAME to the Registered Homenet Domain, the
ZTYPE to SOA, and the ZCLASS to the zone's type. The Prerequisite
section is empty. The Update section is an RRset of type NS with the
NAME set to the Registered Domain Name. As indicated by [RFC2136],
Section 2.5.2, the delete instruction is set initiated by setting the TTL to
0,
the Class CLASS to ANY, and the RDLENGTH to 0, and the RDATA MUST be empty. The
Additional Data section is empty.

Upon receiving the DNS update request, the DM checks the request and
removes the delegation. The DM returns a NOERROR response to
indicate the delegation has been deleted. Similar to what is
described in Section 6.5.2, DNS errors are used, and an error
indicates that the delegation has not been deleted.

6.6. Securing the Control Channel

TLS [RFC8446] MUST be used to secure the transactions between the DM
and the HNA, and the DM and HNA MUST be mutually authenticated. The
DNS exchanges are performed using DNS over TLS [RFC7858].

The HNA may be provisioned by the manufacturer or during some user-
initiated onboarding process, for example, with a browser, by signing
up to a service provider, and with a resulting OAUTH2 OAuth 2.0 token to be
provided to the HNA. Such a process may result in a passing of a
settings from a registrar into the HNA through an http API interface.
(This is not in scope for this document.)

When the HNA connects to the DM's Control Channel, TLS will be used,
and the connection will be mutually authenticated. The DM will
authenticate the HNA's certificate based upon having participated in
some provisioning process that is not standardized by this document.
The results of the provisioning process is a series of settings
described in Appendix A.1.

The HNA will validate the DM's Control Channel certificate by
performing a DNS-ID check on the name as described in [RFC9525].

In the future, other specifications may consider protecting DNS
messages with other transport layers such as DNS over DTLS [RFC8094],
DNS over HTTPS (DoH) [RFC8484], or DNS over QUIC [RFC9250].

7. Synchronization Channel

The DM Synchronization Channel is used for communication between the
HNA and the DM for synchronizing the Public Homenet Zone. Note that
the Control Channel and the Synchronization Channel are different
channels by construction even though they may use the same IP
address. Suppose the HNA and the DM are using a single IP address
designated by XX. XX, and YYYYY and ZZZZZ are the various ports involved
in the communications.

The Control Channel is between

* the HNA working as a client using port number YYYYY (an ephemeral
also commonly designated as a high range port) toward and

* a service provided by the DM at port 853, when using DoT.

On the other hand, the Synchronization Channel is set between

* the DM working as a client using port ZZZZZ (another ephemeral
port) toward and

* a service provided by the HNA at port 853.

As a result, even though the same pair of IP addresses may be
involved, the Control Channel and the Synchronization Channel are
always distinct channels.

Uploading and dynamically updating the zone file on the DM can be
seen as zone provisioning between the HNA (Hidden Primary Server) (hidden primary server) and
the DM (Secondary Server). (secondary server). This is handled using the normal zone
transfer mechanism involving the AXFR and IXFR. Incremental Zone Transfer
(IXFR).

Part of the process to update the zone involves the owner of the zone
(the hidden primary, primary server, the HNA) sending a DNS Notify to the
secondaries. In this situation, the only destination that is known
by the HNA is the DM's Control Channel, so DNS Notifies are sent over
the Control Channel, secured by a mutually authenticated TLS.

Please note that DNS Notifies are not critical to normal operation,
as the DM will be checking the zone regularly based upon SOA record
comments. DNS Notifies do speed things up as they cause the DM to
use the Synchronization Channel to immediately do an SOA query to
detect any updates. If there are any changes, then the DM
immediately transfers the zone updates.

This specification standardizes the use of a primary/secondary
mechanism [RFC1996] rather than an extended series of DNS update
messages. The primary/secondary mechanism was selected as it scales
better and avoids DoS attacks. Because this AXFR runs over a TCP
channel secured by a mutually authenticated TLS, the DNS update is
more complicated.

Note that this document provides no standard way to distribute a DNS
primary between multiple devices. As a result, if multiple devices
are candidates for hosting the Hidden Primary, hidden primary server, some specific
mechanisms should be designed so the home network only selects a
single HNA for the Hidden Primary. hidden primary server. Selection mechanisms based
on HNCP [RFC7788] are good candidates for future work.

7.1. Securing the Synchronization Channel

The Synchronization Channel uses mutually authenticated TLS, as
described by [RFC9103].

There is a TLS client certificate used by the DM to authenticate
itself. The DM uses the same certificate that was configured into
the HNA for authenticating the Control Channel, but as a client
certificate rather than a server certificate.

[RFC9103] makes no requirements or recommendations on any extended
key usage flags for zone transfers, and this document adopts the view
that none should be required. and leave it up Note that once an update to [RFC9103] to get
updated for
is published, this document's normative reference to [RFC9103] will
be considered updated as well.

For the TLS server certificate, the HNA uses the same certificate
that it uses to authenticate itself to the DM for the Control
Channel.

The HNA MAY use this certificate as the authorization for the zone
transfer, or the HNA MAY have been configured with an Access Control
List (ACL) that will determine if the zone transfer can proceed.
This is a local configuration option as it is premature to determine
which will be operationally simpler.

When the HNA expects to do zone transfer authorization by certificate
only, the HNA MAY still apply an ACL on inbound connection requests
to avoid load. In this case, the HNA MUST regularly check (via a DNS
resolution) the validity of the address(es) of the DM in the filter.

8. DM Distribution Channel

The DM Distribution Channel is used for communication between the DM
and the Public Authoritative Servers. The architecture and
communication used for the DM Distribution Channels are outside the
scope of this document, but there are many existing solutions
available, e.g., rsync, DNS AXFR, REST, and DB copy.

9. HNA Security Policies

The HNA, as the hidden primary, primary server, processes only limited message
exchanges on its Internet-facing interface. This should be enforced
using security policies to allow only a subset of DNS requests to be
received by HNA.

The Hidden Primary Server hidden primary server on the HNA differs from the regular
authoritative server for the home network due to the following:

Interface Binding: The Hidden Primary Server hidden primary server will almost certainly
listen on the WAN Interface, whereas a regular Homenet
Authoritative Server will listen on the internal home network
interface.

Limited Exchanges: The purpose of the Hidden Primary Server hidden primary server is to
synchronize with the DM, not to serve any zones to end users or
the public Internet. This results in a limited number of possible
exchanges (AXFR/IXFR) with a small number of IP addresses, and an
implementation MUST enable filtering policies: it should only
respond to queries that are required to do zone transfers. That
list includes SOA queries and AXFR/IXFR queries.

10. Public Homenet Reverse Zone

The Public Homenet Reverse Zone works similarly to the Public Homenet
Zone. The main difference is that the ISP that provides the IPv6
connectivity is likely to also be the owner of the corresponding IPv6
reverse zone who administrates the Reverse Public Authoritative
Servers. The configuration and the setting of the Synchronization
Channel and Control Channel can largely be automated using DHCPv6
messages that are a part of the IPv6 prefix delegation process.

The Public Homenet Zone is associated with a Registered Homenet
Domain, and the ownership of that domain requires a specific
registration from the end user as well as the HNA being provisioned
with some authentication credentials. Such steps are mandatory
unless the DOI has some other means to authenticate the HNA. Such
situation may occur, for example, when the ISP provides the Homenet
Domain as well as the DOI.

In this case, the HNA may be authenticated by the physical link
layer, in which case the authentication of the HNA may be performed
without additional provisioning of the HNA. While this may not be so
common for the Public Homenet Zone, this situation is expected to be
quite common for the Reverse Homenet Zone as the ISP owns the IP
address or IP prefix.

More specifically, a common case is that the upstream ISP provides
the IPv6 prefix to the Homenet with an identity association for a
prefix delegation (IA_PD) option [RFC8415] and manages the DOI of the
associated reverse zone.

This leaves a place for setting up the relation between the HNA and
DOI automatically as described in [RFC9527].

In the case of the reverse zone, the DOI authenticates the source of
the updates by IPv6 ACLs, and the ISP knows exactly what addresses
have been delegated. Therefore, the HNA SHOULD always originate
Synchronization Channel updates from an IP address within the zone
that is being updated. Exceptionally, the Synchronization Channel
might be from a different zone delegated to the HNA (if there were
multiple zones or renumbering events were in progress).

For example, if the ISP has assigned 2001:db8:f00d::/64 2001:db8:f00d:1234::/64 to the
WAN interface (by DHCPv6 or PPP and with Router Advertisement (RA)), then
the HNA should originate Synchronization Channel updates from, for
example, 2001:db8:f00d::2.

An 2001:db8:f00d:1234::2.

If an ISP that has delegated 2001:db8:aeae::/56 to the HNA via DHCPv6-PD,
then the HNA should originate Synchronization Channel updates to an
IP address within that subnet, such as 2001:db8:aeae:1::2.

With this relation automatically configured, the synchronization
between the Home network and the DOI happens in a similar way to the
synchronziation
synchronization of the Public Homenet Zone described earlier in this
document.

Note that for home networks connected to by multiple ISPs, each ISP
provides only the DOI of the reverse zones associated with the
delegated prefix. It is also likely that the DNS exchanges will need
to be performed on dedicated interfaces to be accepted by the ISP.
More specifically, the reverse zone update associated with prefix 1 will not
be able to
cannot be performed by the HNA using an IP address that belongs to
prefix 2. Such constraints do not raise major concerns for hot
standby or load-sharing configuration.

With IPv6, the reverse domain space for IP addresses associated with
a subnet such as ::/64 is so large that the reverse zone may be
confronted with scalability issues. How the reverse zone is
generated is out of scope of this document. [RFC8501] provides
guidance on how to address scalability issues.

11. DNSSEC-Compliant Homenet Architecture

Section 3.7.3 of [RFC7368] recommends that DNSSEC be deployed on both
the authoritative server and the resolver.

The resolver side is out of scope of this document, and only the
authoritative part of the server is considered. Other documents such
as [RFC5011] deal with the continuous update of trust anchors
required for operation of a DNSSEC resolver. Resolver.

The Public Homenet Zone and the Public Reverse Zone MUST be DNSSEC
signed by the HNA.

Secure delegation is achieved only if the DS RRset is properly set in
the parent zone. Secure delegation can be performed by the HNA or
the DOIs, and the choice highly depends on which entity is authorized
to perform such updates. Typically, the DS RRset is updated manually
through a registrar interface and can be maintained with mechanisms
such as CDS [RFC7344].

When the operator of the DOI is also the registrar for the domain,
then it is a trivial matter for the DOI to initialize the relevant DS
records in the parent zone. In other cases, some other
initialization will be required, and that will be specific to the
infrastructure involved. It is beyond the scope of this document.

There may be some situations where the HNA is unable to arrange for
secure delegation of the zones, but the HNA MUST still sign the
zones.

12. Renumbering

During a renumbering of the home network, the HNA IP address may be
changed and the Public Homenet Zone will be updated by the HNA with
new AAAA records.

The HNA will then advertise to the DM via a NOTIFY on the Control
Channel. The DM will need to note the new originating IP for the
connection, and it will need to update its internal database of
Synchronization Channels. A new zone transfer will occur with the
new records for the resources that the HNA wishes to publish.

The remainder of the section provides recommendations regarding the
provisioning of the Public Homenet Zone, especially the IP addresses.

Renumbering has been extensively described in [RFC4192] and analyzed
in [RFC7010], and the reader is expected to be familiar with them
before reading this section. In the make-before-break renumbering
scenario, the new prefix is advertised, and the network is configured
to prepare the transition to the new prefix. During a period of
time, the two prefixes (old and new) coexist before the old prefix is
completely removed. New resource records containing the new prefix
SHOULD be published, while the old resource records with the old
prefixes SHOULD be withdrawn. If the HNA anticipates that the period
of overlap will be long (perhaps due to the knowledge of router and
DHCPv6 lifetimes), it MAY publish the old prefixes with a
significantly lower TTL.

In break-before-make renumbering scenarios, including flash
renumbering scenarios [RFC8978], the old prefix becomes unusable
before the new prefix is known or advertised. As explained in
[RFC8978], some flash renumberings occur due to power cycling of the
HNA, where ISPs do not properly remember what prefixes have been
assigned to which user.

An HNA that boots up MUST immediately use the Control Channel to
update the location for the Synchronization Channel. This is a
reasonable thing to do on every boot, as the HNA has no idea how long
it has been offline or if the (DNSSEC) zone has perhaps expired
during the time the HNA was powered off.

The HNA will have a list of names that should be published, but it
might not yet have IP addresses for those devices. This could be
because at the time of power on, the other devices were not yet
online. If the HNA is sure that the prefix has not changed, then it
should use the previously known addresses, with a very low TTL.

Although the new and old IP addresses may be stored in the Public
Homenet Zone, it is RECOMMENDED that only the newly reachable IP
addresses be published.

Regarding the Public Homenet Reverse Zone, the new Public Homenet
Reverse Zone has to be populated as soon as possible, and the old
Public Homenet Reverse Zone will be deleted by the owner of the zone
(and the owner of the old prefix, which is usually the ISP) once the
prefix is no longer assigned to the HNA. The ISP MUST ensure that
the DNS cache has expired before reassigning the prefix to a new home
network. This may be enforced by controlling the TTL values.

To avoid reachability disruption, IP connectivity information
provided by the DNS MUST be coherent with the IP in use. In our
case, this means the old IP address MUST NOT be provided via the DNS
when it is not reachable anymore.

In the make-before-break scenario, it is possible to make the
transition seamless. Let T be the TTL associated with an RRset of
the Public Homenet Zone; Time_NEW be the time the new IP address
replaces the old IP address in the Homenet Zone; and
Time_OLD_UNREACHABLE be the time the old IP will not be reachable
anymore.

In the case of the make-before-break scenario, seamless reachability
is provided as long as Time_OLD_UNREACHABLE - T_NEW > (2 * T). If
this is not satisfied, then devices associated with the old IP
address in the home network may become unreachable for 2 * T -
(Time_OLD_UNREACHABLE - Time_NEW).

In the case of a break-before-make scenario, Time_OLD_UNREACHABLE =
Time_NEW, and the device may become unreachable up to 2 * T. Of
course, if Time_NEW >= Time_OLD_UNREACHABLE, then the outage is not
seamless.

13. Privacy Considerations

Outsourcing the DNS Authoritative service from the HNA to a third
party raises a few privacy-related concerns.

The Public Homenet Zone lists the names of services hosted in the
home network. Combined with blocking of AXFR queries, the use of
NSEC3 [RFC5155] (vs. NSEC [RFC4034]) prevents an attacker from being
able to walk the zone to discover all the names. However, recent
work [GPUNSEC3] [ZONEENUM] has shown that the protection provided by
NSEC3 against dictionary attacks should be considered cautiously, and
[RFC9276] provides guidelines to configure NSEC3 properly. In
addition, the attacker may be able to walk the reverse DNS zone or
use other reconnaissance techniques to learn this information as
described in [RFC7707].

The zone may be also exposed during the synchronization between the
primary and the secondary. The casual risk of this occurring is low,
and the use of [RFC9103] significantly reduces this. Even if DNS
zone transfer over TLS [RFC9103] is used by the DOI, it may still
leak the existence of the zone through Notifies. The protocol
described in this document does not increase that risk, as all
Notifies use the encrypted Control Channel.

In general, a home network owner is expected to publish only names
for which there is some need to reference them externally.
Publication of the name does not imply that the service is
necessarily reachable from any or all parts of the Internet.
[RFC7084] mandates that the outgoing-only policy [RFC6092] be
available, and in many cases, it is configured by default. A well-
designed user interface would combine a policy for making a service
public by a name with a policy on who may access it.

In many cases, and for privacy reasons, the home network owner has
wanted to publish names only for services that they will be able to
access. The access control may consist of an IP source address
range, or access may be restricted via some VPN functionality. The
main advantages of publishing the names are that the service may be
accessed by the same name both within and outside the home, and the
DNS resolution can be handled similarly both within and outside the
home. This considerably eases the ability to use VPNs where the VPN
can be chosen according to the IP address of the service. Typically,
a user may configure its device to reach its Homenet devices via a
VPN while the remaining traffic is accessed directly.

Enterprise networks have generally adopted another strategy
designated as split-horizon-DNS. While such strategy might appear as
providing more privacy at first sight, its implementation remains
challenging and the privacy advantages need to be considered
carefully. In split-horizon-DNS, names are designated with internal
names that can only be resolved within the corporate network. When
such strategy is applied to the homenet, VPNs need to be configured
with naming resolution policies and routing policies. Such an
approach might be reasonable with a single VPN, but maintaining a
coherent DNS space and IP space among various VPNs comes with serious
complexities. Firstly, if multiple homenets are using the same
domain name -- like home.arpa -- it becomes difficult to determine on
which network the resolution should be performed. As a result,
homenets should at least be differentiated by a domain name.
Secondly, the use of split-horizon-DNS requires each VPN to be
associated with a resolver and specific resolutions to be performed
by the dedicated resolver. Such policies can easily raise some
conflicts (with significant privacy issues) while remaining hard to
be implemented.

In addition to the Public Homenet Zone, pervasive DNS monitoring can
also monitor the traffic associated with the Public Homenet Zone.
This traffic may provide an indication of the services an end user
accesses, plus how and when they use these services. Although,
caching may obfuscate this information inside the home network, it is
likely that this information will not be cached outside the home
network.

14. Security Considerations

The HNA never answers DNS requests from the Internet. These requests
are instead served by the DOI.

While this limits the level of exposure of the HNA, the HNA still has
some exposure to attacks from the Internet. This section analyses
the attack surface associated with these communications, the data
published by the DOI, as well as operational considerations.

14.1. Registered Homenet Domain

The DOI MUST NOT serve any Public Homenet Zone when it is not
confident that the HNA owns the Registered Homenet Domain. Proof of
ownership is outside the scope of this document, and it is assumed
that such a phase has preceded the outsourcing of the zone.

14.2. HNA DM Channels

The channels between HNA and DM are mutually authenticated and
encrypted with TLS [RFC8446], and its associated security
considerations apply.

To ensure that the multiple TLS sessions are continuously
authenticating the same entity, TLS may take advantage of second-
factor authentication as described in [RFC8672] for the TLS server
certificate for the Control Channel. The HNA should also cache the
TLS server certificate used by the DM, in order to authenticate the
DM during the setup of the Synchronization Channel. (Alternatively,
the HNA is configured with an ACL from which Synchronization Channel
connections will originate.)

The Control Channel and Synchronization Channel follow the guidelines
in [RFC7858] and [RFC9103], respectively.

The DNS protocol is subject to reflection attacks; however, these
attacks are largely applicable when DNS is carried over UDP. The
interfaces between the HNA and DM are using TLS over TCP, which
prevents such reflection attacks. Note that Public Authoritative
servers hosted by the DOI are subject to such attacks, but that is
out of scope of this document.

Note that in the case of the Reverse Homenet Zone, the data is less
subject to attacks than in the Public Homenet Zone. In addition, the
DM and Reverse Distribution Manager (RDM) may be provided by the ISP
-- as described in [RFC9527], in which case DM and RDM might be less
exposed to attacks -- as communications within a network.

14.3. Names Are Less Secure than IP Addresses

This document describes how an end user can make their services and
devices from their home network reachable on the Internet by using
names rather than IP addresses. This exposes the home network to
attackers because names are expected to include less entropy than IP
addresses. IPv4 addresses are 4-bytes long leading to 2^32
possibilities. With IPv6 addresses, the Interface Identifier is
64-bits long leading to up to 2^64 possibilities for a given
subnetwork. This is not to mention that the subnet prefix is also
64-bits long, thus providing up to 2^64 possibilities. On the other
hand, names used for either the home network domain or the devices
present less entropy (livebox, router, printer, nicolas, jennifer,
...) and thus potentially expose the devices to dictionary attacks.

14.4. Names Are Less Volatile than IP Addresses

IP addresses may be used to locate a device, a host, or a service.
However, home networks are not expected to be assigned a time-
invariant prefix by ISPs. In addition, IPv6 enables temporary
addresses that makes them even more volatile [RFC8981]. As a result,
observing IP addresses only provides some ephemeral information about
who is accessing the service. On the other hand, names are not
expected to be as volatile as IP addresses. As a result, logging
names over time may be more valuable than logging IP addresses,
especially to profile an end user's characteristics.

PTR provides a way to bind an IP address to a name. In that sense,
responding to PTR DNS queries may affect the end user's privacy. For
that reason, PTR DNS queries MAY be configured to return with
NXDOMAIN instead.

14.5. Deployment Considerations

The HNA is expected to sign the DNSSEC zone and, as such, hold the
private KSK and Zone Signing Key (ZSK).

In this case, there is no strong justification to use a separate KSK
and ZSK. If an attacker can get access to one of them, it is likely
that they will access both of them. If the HNA is run in a home
router with a secure element (SE) or trusted platform module (TPM),
storing the private keys in the secure element would be a useful
precaution. The DNSSEC keys are generally needed on an hourly to
weekly basis, but not more often.

While there is some risk that the DNSSEC keys might be disclosed by
malicious parties, the bigger risk is that they will simply be lost
if the home router is factory reset or just thrown out / replaced
with a newer model.

Generating new DNSSEC keys is relatively easy; they can be deployed
using the Control Channel to the DM. The key that is used to
authenticate that connection is the critical key that needs
protection and should ideally be backed up to offline storage (such
as a USB key).

14.6. Operational Considerations

Homenet technologies make it easier to expose devices and services to
the Internet. This imposes broader operational considerations for
the operator and the Internet as follows:

* The home network operator must carefully assess whether a device
or service previously fielded only on a home network is robust
enough to be exposed to the Internet.

* The home network operator will need to increase the diligence to
regularly managing these exposed devices due to their increased
risk posture of being exposed to the Internet.

* Depending on the operational practices of the home network
operators, there is an increased risk to the Internet through the
possible introduction of additional Internet-exposed systems that
are poorly managed and likely to be compromised.

15. IANA Considerations

This document has no IANA actions.

16. References

16.1. Normative References

[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>.

[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC 1918, DOI 10.17487/RFC1918,
February 1996, <https://www.rfc-editor.org/info/rfc1918>.

[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.

[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>.

[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, DOI 10.17487/RFC3007, November 2000,
<https://www.rfc-editor.org/info/rfc3007>.

[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>.

[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
<https://www.rfc-editor.org/info/rfc5155>.

[RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
DNSSEC Delegation Trust Maintenance", RFC 7344,
DOI 10.17487/RFC7344, September 2014,
<https://www.rfc-editor.org/info/rfc7344>.

[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>.

[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>.

[RFC8375] Pfister, P. and T. Lemon, "Special-Use Domain
'home.arpa.'", RFC 8375, DOI 10.17487/RFC8375, May 2018,
<https://www.rfc-editor.org/info/rfc8375>.

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

[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/info/rfc8499>.

[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>.

[RFC9525] Saint-Andre, P. and R. Salz, "Service Identity in TLS",
RFC 9525, DOI 10.17487/RFC9525, November 2023,
<https://www.rfc-editor.org/info/rfc9525>.

16.2. Informative References

[DOMAIN-VALIDATION]
Sahib, S., Huque, S., Wouters, P., and E. Nygren, "Domain
Control Validation using DNS", Work in Progress, Internet-
Draft, draft-ietf-dnsop-domain-verification-techniques-03,
17 October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-dnsop-domain-verification-techniques-03>.

[DRO-RECS] Migault, D., Lewis, E., and D. York, "Recommendations for
DNSSEC Resolvers Operators", Work in Progress, Internet-
Draft, draft-ietf-dnsop-dnssec-validator-requirements-07,
13 November 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-dnsop-dnssec-validator-requirements-07>.

[GPUNSEC3] Wander, M., Schwittmann, L., Boelmann, C., and T. Weis,
"GPU-Based NSEC3 Hash Breaking", DOI 10.1109/NCA.2014.27,
August 2014, <https://doi.org/10.1109/NCA.2014.27>.

[HOMEROUTER-PROVISION]
Richardson, M., "Provisioning Initial Device Identifiers
into Home Routers", Work in Progress, Internet-Draft,
draft-richardson-homerouter-provisioning-02, 14 November
2021, <https://datatracker.ietf.org/doc/html/draft-
richardson-homerouter-provisioning-02>.

[NS-REVALIDATION]
Huque, S., Vixie, P., and R. Dolmans, "Delegation
Revalidation by DNS Resolvers", Work in Progress,
March 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-dnsop-ns-revalidation-04>.

[REBIND] Wikipedia, "DNS rebinding", September 2023,
<https://en.wikipedia.org/w/
index.php?title=DNS_rebinding&oldid=1173433859>.

[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>.

[RFC3787] Parker, J., Ed., "Recommendations for Interoperable IP
Networks using Intermediate System to Intermediate System
(IS-IS)",

[RFC3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
Unicast Address Format", RFC 3787, 3587, DOI 10.17487/RFC3787, May 2004,
<https://www.rfc-editor.org/info/rfc3787>. 10.17487/RFC3587,
August 2003, <https://www.rfc-editor.org/info/rfc3587>.

[RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
Configuration of IPv4 Link-Local Addresses", RFC 3927,
DOI 10.17487/RFC3927, May 2005,
<https://www.rfc-editor.org/info/rfc3927>.

[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
DOI 10.17487/RFC4192, September 2005,
<https://www.rfc-editor.org/info/rfc4192>.

[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.

[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.

[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,
September 2007, <https://www.rfc-editor.org/info/rfc5011>.

[RFC6092] Woodyatt, J., Ed., "Recommended Simple Security
Capabilities in Customer Premises Equipment (CPE) for
Providing Residential IPv6 Internet Service", RFC 6092,
DOI 10.17487/RFC6092, January 2011,
<https://www.rfc-editor.org/info/rfc6092>.

[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.

[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.

[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.

[RFC7010] Liu, B., Jiang, S., Carpenter, B., Venaas, S., and W.
George, "IPv6 Site Renumbering Gap Analysis", RFC 7010,
DOI 10.17487/RFC7010, September 2013,
<https://www.rfc-editor.org/info/rfc7010>.

[RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
Requirements for IPv6 Customer Edge Routers", RFC 7084,
DOI 10.17487/RFC7084, November 2013,
<https://www.rfc-editor.org/info/rfc7084>.

[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>.

[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404,
DOI 10.17487/RFC7404, November 2014,
<https://www.rfc-editor.org/info/rfc7404>.

[RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<https://www.rfc-editor.org/info/rfc7707>.

[RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
2016, <https://www.rfc-editor.org/info/rfc7788>.

[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>.

[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>.

[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.

[RFC8501] Howard, L., "Reverse DNS in IPv6 for Internet Service
Providers", RFC 8501, DOI 10.17487/RFC8501, November 2018,
<https://www.rfc-editor.org/info/rfc8501>.

[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>.

[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.

[RFC8672] Sheffer, Y. and D. Migault, "TLS Server Identity Pinning
with Tickets", RFC 8672, DOI 10.17487/RFC8672, October
2019, <https://www.rfc-editor.org/info/rfc8672>.

[RFC8978] Gont, F., Žorž, J., and R. Patterson, "Reaction of IPv6
Stateless Address Autoconfiguration (SLAAC) to Flash-
Renumbering Events", RFC 8978, DOI 10.17487/RFC8978, March
2021, <https://www.rfc-editor.org/info/rfc8978>.

[RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves,
"Temporary Address Extensions for Stateless Address
Autoconfiguration in IPv6", RFC 8981,
DOI 10.17487/RFC8981, February 2021,
<https://www.rfc-editor.org/info/rfc8981>.

[RFC9250] Huitema, C., Dickinson, S., and A. Mankin, "DNS over
Dedicated QUIC Connections", RFC 9250,
DOI 10.17487/RFC9250, May 2022,
<https://www.rfc-editor.org/info/rfc9250>.

[RFC9276] Hardaker, W. and V. Dukhovni, "Guidance for NSEC3
Parameter Settings", BCP 236, RFC 9276,
DOI 10.17487/RFC9276, August 2022,
<https://www.rfc-editor.org/info/rfc9276>.

[RFC9527] Migault, D., Weber, R., and T. Mrugalski, "DHCPv6 Options
for Home Network the Homenet Naming Authority", RFC 9527,
DOI 10.17487/RFC9527, December 2023, January 2024,
<https://www.rfc-editor.org/info/rfc9527>.

[ZONEENUM] Wang, Z., Xiao, L., and R. Wang, "An efficient DNSSEC zone
enumeration algorithm", DOI 10.2495/MIIT130591, April
2014, <https://doi.org/10.2495/MIIT130591>.

Appendix A. HNA Channel Configurations

A.1. Homenet Public Homenet Zone

This document does not deal with how the HNA is provisioned with a
trusted relationship to the Distribution Manager for the forward
zone.

This section details what needs to be provisioned into the HNA and
serves as a requirements statement for mechanisms.

The HNA needs to be provisioned with:

* the Registered Domain (e.g., myhome.example);

* the contact information for the DM, including the DNS name (the
fully qualified domain name (FQDN)), possibly the IP literal, and
a certificate (or anchor) to be used to authenticate the service;

* the DM transport protocol and port (the default is DNS over TLS,
on port 853); and

* the HNA credentials used by the DM for its authentication.

The HNA will need to select an IP address for communication for the
Synchronization Channel. This is typically the WAN address of the
CPE, but it could be an IPv6 LAN address in the case of a home with
multiple ISPs (and multiple border routers). This is detailed in
Section 6.5.3 when the NS and A or AAAA RRsets are communicated.

The above parameters MUST be provisioned for ISP-specific reverse
zones. One example of how to do this can be found in [RFC9527].
ISP-specific forward zones MAY also be provisioned using [RFC9527],
but zones that are not related to a specific ISP zone (such as with a
DNS provider) must be provisioned through other means.

Similarly, if the HNA is provided by a registrar, the HNA may be
handed preconfigured to the end user.

In the absence of specific pre-established relations, these pieces of
information may be entered manually by the end user. In order to
ease the configuration from the end user, the following scheme may be
implemented.

The HNA may present the end user with a web interface that provides
the end user the ability to indicate the Registered Homenet Domain or
the registrar with, for example, a preselected list. Once the
registrar has been selected, the HNA redirects the end user to that
registrar in order to receive an access token. The access token will
enable the HNA to retrieve the DM parameters associated with the
Registered Domain. These parameters will include the credentials
used by the HNA to establish the Control and Synchronization
Channels.

Such architecture limits the necessary steps to configure the HNA
from the end user.

Appendix B. Information Model for Outsourced Information

This section specifies an optional format for the set of parameters
required by the HNA to configure the naming architecture of this
document.

In cases where a home router has not been provisioned by the
manufacturer (when forward zones are provided by the manufacturer) or
by the ISP (when the ISP provides this service), then a home user/
owner will need to configure these settings via an administrative
interface.

By defining a standard format (in JSON) for this configuration
information, the user/owner may be able to copy and paste a
configuration blob from the service provider into the administrative
interface of the HNA.

This format may also provide the basis for a future OAUTH2 OAuth 2.0
[RFC6749] flow that could do the set up automatically.

The HNA needs to be configured with the following parameters as
described by the Concise Data Definition Language (CDDL) [RFC8610].
These parameters are necessary to establish a secure channel between
the HNA and the DM as well as to specify the DNS zone that is in the
scope of the communication.

hna-configuration = {
"registered_domain" : tstr,
"dm" : tstr,
? "dm_transport" : "DoT"
? "dm_port" : uint,
? "dm_acl" : hna-acl / [ +hna-acl ]
? "hna_auth_method": hna-auth-method
? "hna_certificate": tstr
}

hna-acl = tstr
hna-auth-method /= "certificate"

For example:

{
"registered_domain" : "n8d234f.r.example.net",
"dm" : "2001:db8:1234:111:222::2",
"dm_transport" : "DoT",
"dm_port" : 4433,
"dm_acl" : "2001:db8:1f15:62e:21c::/64" "2001:db8:1f15:62e::/64"
or [ "2001:db8:1f15:62e:21c::/64", "2001:db8:1f15:62e::/64", ... ]
"hna_auth_method" : "certificate",
"hna_certificate" : "-----BEGIN CERTIFICATE-----\nMIIDTjCCFGy..",
}

Registered Homenet Domain (registered_domain): The Domain Name of
the zone. Multiple Registered Homenet Domains may be provided.
This will generate the creation of multiple Public Homenet Zones.
This parameter is mandatory.

Distribution Manager notification address (dm): The associated FQDNs
or IP addresses of the DM to which DNS Notifies should be sent.
This parameter is mandatory. IP addresses are optional, and the
FQDN is sufficient and preferred. If there are concerns about the
security of the name to IP translation, then DNSSEC should be
employed.

As the session between the HNA and the DM is authenticated with TLS,
the use of names is easier.

As certificates are more commonly emitted for FQDN than for IP
addresses, it is preferred to use names and authenticate the name of
the DM during the TLS session establishment.

Supported Transport (dm_transport): The transport that carries the
DNS exchanges between the HNA and the DM. The typical value is
"DoT", but it may be extended in the future with "DoH" or "DoQ",
for example. This parameter is optional, and the HNA uses DoT by
default.

Distribution Manager Port (dm_port): Indicates the port used by the
DM. This parameter is optional, and the default value is provided
by the Supported Transport. In the future, an additional
transport may not have a default port, in which case either a
default port needs to be defined or this parameter becomes
mandatory.

Note that HNA does not define ports for the Synchronization Channel.
In any case, this is not expected to be a part of the configuration
but is instead negotiated through the Configuration Channel.
Currently, the Configuration Channel does not provide this and limits
its agility to a dedicated IP address. If such agility is needed in
the future, additional exchanges will need to be defined.

Authentication Method ("hna_auth_method"): How the HNA authenticates
itself to the DM within the TLS connection(s). The authentication
method can typically be "certificate", "psk", or "none". This
parameter is optional, and the Authentication Method is
"certificate" by default.

Authentication data ("hna_certificate", "hna_key"): The certificate
chain used to authenticate the HNA. This parameter is optional,
and when not specified, a self-signed certificate is used.

Distribution Manager AXFR permission netmask (dm_acl): The subnet
from which the CPE should accept SOA queries and AXFR requests. A
subnet is used in the case where the DOI consists of a number of
different systems. An array of addresses is permitted. This
parameter is optional, and if unspecified, the CPE uses the IP
addresses provided by the dm parameter either directly when the dm
indicates the IP address(es) returned by the DNS(SEC) DNS or DNSSEC
resolution when dm indicates an FQDN.

For forward zones, the relationship between the HNA and the forward
zone provider may be the result of a number of transactions:

1. The forward zone outsourcing may be provided by the maker of the
Homenet router. In this case, the identity and authorization
could be built in the device at the manufacturer provisioning
time. The device would need to be provisioned with a device-
unique credential, and it is likely that the Registered Homenet
Domain would be derived from a public attribute of the device,
such as a serial number (see Appendix C or [HOMEROUTER-PROVISION]
for more details).

2. The forward zone outsourcing may be provided by the ISP. In this
case, the use of [RFC9527] to provide the credentials is
appropriate.

3. The forward zone may be outsourced to a third party, such as a
domain registrar. In this case, the use of the JSON-serialized
YANG data model described in this section is appropriate, as it
can easily be copy and pasted by the user or downloaded as part
of a web transaction.

For reverse zones, the relationship is always with the upstream ISP
(although there may be more than one), so [RFC9527] is always the
appropriate interface. applies.

The following is an abridged example of a set of data that represents
the needed configuration parameters for outsourcing.

Appendix C. Example: A Manufacturer-Provisioned HNA Product Flow

This scenario is one where a Homenet router device manufacturer
decides to offer DNS hosting as a value add.

[HOMEROUTER-PROVISION] describes a process for a home router
credential provisioning system. The outline of it is that near the
end of the manufacturing process, as part of the firmware loading,
the manufacturer provisions a private key and certificate into the
device.

In addition to having an asymmetric credential known to the
manufacturer, the device also has been provisioned with an agreed-
upon name. In the example in the above document, the name
"n8d234f.r.example.net" has already been allocated and confirmed with
the manufacturer.

The HNA can use the above domain for itself. It is not very pretty
or personal, but if the owner would like to have a better name, they
can arrange it.

The configuration would look like the following:

{
"dm" : "2001:db8:1234:111:222::2",
"dm_acl" : "2001:db8:1234:111:222::/64",
"dm_ctrl" : "manufacturer.example.net",
"dm_port" : "4433",
"ns_list" : [ "ns1.publicdns.example", "ns2.publicdns.example"],
"zone" : "n8d234f.r.example.net",
"auth_method" : "certificate",
"hna_certificate":"-----BEGIN CERTIFICATE-----\nMIIDTjCCFGy....",
}

The dm_ctrl and dm_port values would be built into the firmware.

Acknowledgments

The authors wish to thank Philippe Lemordant for his contributions to
the earlier draft versions of this document; Ole Troan for pointing
out issues with the IPv6-routed home concept and placing the scope of
this document in a wider picture; Mark Townsley for encouragement and
injecting a healthy debate on the merits of the idea; Ulrik de Bie
for providing alternative solutions; Paul Mockapetris, Christian
Jacquenet, Francis Dupont, and Ludovic Eschard for their remarks on
HNA and low power devices; Olafur Gudmundsson for clarifying DNSSEC
capabilities of small devices; Simon Kelley for its feedback as
dnsmasq implementer; Andrew Sullivan, Mark Andrew, Ted Lemon, Mikael
Abrahamson, Stephen Farrell, and Ray Bellis for their feedback on
handling different views as well as clarifying the impact of
outsourcing the zone-signing operation outside the HNA; and Mark
Andrew and Peter Koch for clarifying the renumbering.

The authors would like to thank Kiran Makhijani for her in-depth
review that contributed to shaping the final version of this
document.

The authors would also like to thank our Area Director Éric Vyncke
for his constant support and pushing the document through the IESG
process and the many reviewers from various directorates including
Anthony Somerset, Geoff Huston, Tim Chown, Tim Wicinski, Matt Brown,
Darrel Miller, and Christer Holmberg.

Contributors

The coauthors would like to thank Chris Griffiths and Wouter Cloetens
for providing significant contributions to the earlier 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
Nominum
2000 Seaport Blvd.
Redwood City, CA 94063
United States of America
Email: ralf.weber@nominum.com

Michael Richardson
Sandelman Software Works
470 Dawson Avenue
Ottawa ON K1Z 5V7
Canada
Email: mcr+ietf@sandelman.ca

Ray Hunter
Globis Consulting BV
Weegschaalstraat 3
5632CW Eindhoven
Netherlands
Email: v6ops@globis.net