DHCPv6 Options for the Homenet Naming Authority
Extracted elements (22)
No explicit port is encoded in the DHCPv6 options; the default port for the selected transport is used (853 for DomTLS per RFC 7858/RFC 9103). This simplifies the option format by avoiding a list of (transport, port) tuples, at the cost of requiring out-of-band coordination if the default port is occupied.
The DM and RDM are identified by FQDN rather than IP address because an FQDN is smaller (avoids listing both IPv4 and IPv6), is a more stable identifier, and can serve as a pointer to additional future metadata needed to establish the HNA-to-DM channel.
Using DHCPv6 to provision the HNA makes the naming outsourcing configuration transparent to the end user and grants the provisioned data the same implicit trust as the IP prefix delegated by the ISP, enabling zero-configuration home network naming.
An end user can redirect a third-party domain (e.g., example.com) to the ISP-assigned Registered Homenet Domain using CNAME, DNAME, or CNAME+DNAME redirection, enabling use of a custom domain without changing the HNA outsourcing configuration.
The DHCPv6 options and protocol are fully compatible with an HNA connected to multiple ISPs, each providing a different Registered Homenet Domain; however, handling multiple simultaneous Registered Homenet Domains is an implementation matter outside the scope of this document.
In OPTION_FORWARD_DIST_MANAGER, the bit for DNS over mutually authenticated TLS (DomTLS) MUST be set; a DM MAY additionally indicate support for multiple transport modes.
In OPTION_REVERSE_DIST_MANAGER, the DomTLS bit MUST be set; an RDM MAY indicate support for multiple transport modes via additional bits.
New entries in the Supported Transport registry MUST specify the bit position, transport protocol description, a mnemonic, and a reference; future code points are assigned under the RFC Required policy per RFC 8126.
The DHCPv6 client MUST include OPTION_REGISTERED_DOMAIN, OPTION_FORWARD_DIST_MANAGER, and OPTION_REVERSE_DIST_MANAGER codes in its Option Request Option (ORO) as specified in RFC 8415 Sections 18.2 and 21.7.
The DHCPv6 server sends the Registered Homenet Domain, Distribution Manager, and Reverse Distribution Manager options only when configured with specific values and when requested by the client via ORO, per RFC 8415 Section 18.3.
Upon receiving the DHCPv6 options defined in this document in a Reply message, the HNA SHOULD proceed as described in RFC 9526 to outsource its Public Homenet Zone or Homenet Reverse Zone.
OPTION_FORWARD_DIST_MANAGER (code 146) provides the HNA with the FQDN of the Distribution Manager (DM) and a 16-bit Supported Transport bitmask indicating the protocols the DM accepts for HNA-to-DM communication.
OPTION_REGISTERED_DOMAIN (code 145) carries the fully qualified domain name (FQDN) associated with the home network, enabling the ISP to provision the HNA with its Registered Homenet Domain via DHCPv6.
OPTION_REVERSE_DIST_MANAGER (code 147) provides the HNA with the FQDN of the Reverse Distribution Manager (RDM) and a 16-bit Supported Transport bitmask for the reverse-zone outsourcing channel.
The Supported Transport field is a 16-bit bitmask where each bit represents a specific transport protocol; bit 0 (least significant) designates DomTLS (DNS over mutually authenticated TLS, default port 853), and bits 1–15 are unassigned.
IANA assigned three new DHCPv6 Option Codes: 145 (OPTION_REGISTERED_DOMAIN, client ORO yes, not singleton), 146 (OPTION_FORWARD_DIST_MANAGER, client ORO yes, singleton), and 147 (OPTION_REVERSE_DIST_MANAGER, client ORO yes, singleton) in the existing DHCPv6 'Option Codes' registry.
IANA created a new 'Supported Transport' registry under the DHCPv6 parameters registry. The initial entry is bit 0 = DomTLS (DNS over mutually authenticated TLS); bits 1–15 are unassigned. Future assignments require RFC Required.
The trust level of the DHCPv6 options defined here is comparable to that of the IP prefix provisioned via DHCPv6; an attacker who can subvert DHCPv6 can redirect the HNA to a malicious DM or RDM. The security considerations of RFC 8415 apply.
TLS authentication of the HNA to the DM/RDM is mandatory; the HNA is expected to be provisioned with a certificate, which may be self-signed when the ISP identifies the HNA by its physical wire line.
OPTION_FORWARD_DIST_MANAGER encodes a 16-bit option-code (146), 16-bit option-len, a 16-bit Supported Transport field (bitmask), and a variable-length Distribution Manager FQDN encoded per RFC 8415 Section 10.
OPTION_REGISTERED_DOMAIN encodes a 16-bit option-code (145), a 16-bit option-len, and a variable-length Registered Homenet Domain FQDN encoded per RFC 8415 Section 10 (DNS label encoding).
OPTION_REVERSE_DIST_MANAGER encodes a 16-bit option-code (147), 16-bit option-len, a 16-bit Supported Transport bitmask, and a variable-length Reverse Distribution Manager FQDN encoded per RFC 8415 Section 10.