



DNS Operations                                                  A. Ferro
Internet-Draft                                                 ApertoDNS
Intended status: Standards Track                         17 January 2026
Expires: 21 July 2026


        ApertoDNS Protocol: A Modern Dynamic DNS Update Protocol
                draft-ferro-dnsop-apertodns-protocol-01

Abstract

   This document specifies the ApertoDNS Protocol, a modern RESTful
   protocol for dynamic DNS (DDNS) updates.  It provides a secure,
   provider-agnostic alternative to legacy protocols, with native
   support for IPv4, IPv6, bulk updates, automatic IP detection, TXT
   record management for ACME DNS-01 challenges, and standardized
   authentication mechanisms.

   The protocol uses well-known URIs (RFC 8615), JSON payloads (RFC
   8259), and bearer token authentication (RFC 6750) to enable
   interoperable dynamic DNS services across different providers.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 21 July 2026.

Copyright Notice

   Copyright (c) 2026 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



Ferro                     Expires 21 July 2026                  [Page 1]

Internet-Draft             ApertoDNS Protocol               January 2026


   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Protocol Versioning . . . . . . . . . . . . . . . . . . .   4
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
     1.3.  Goals . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Base URL  . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Content Type  . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Response Format . . . . . . . . . . . . . . . . . . . . .   6
   4.  Conformance Requirements  . . . . . . . . . . . . . . . . . .   6
     4.1.  Conformance Levels  . . . . . . . . . . . . . . . . . . .   6
     4.2.  Capability Advertisement  . . . . . . . . . . . . . . . .   7
     4.3.  Interoperability  . . . . . . . . . . . . . . . . . . . .   7
   5.  Authentication  . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Supported Methods . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Token Format  . . . . . . . . . . . . . . . . . . . . . .   7
     5.3.  Token Transmission  . . . . . . . . . . . . . . . . . . .   8
   6.  Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Discovery Endpoint (/info)  . . . . . . . . . . . . . . .   8
       6.1.1.  Response Fields . . . . . . . . . . . . . . . . . . .   8
       6.1.2.  Capability Fields . . . . . . . . . . . . . . . . . .   9
       6.1.3.  Example Response  . . . . . . . . . . . . . . . . . .  10
     6.2.  Health Endpoint (/health) . . . . . . . . . . . . . . . .  11
       6.2.1.  Example Response  . . . . . . . . . . . . . . . . . .  11
     6.3.  Update Endpoint (/update) . . . . . . . . . . . . . . . .  11
       6.3.1.  Request Fields  . . . . . . . . . . . . . . . . . . .  11
       6.3.2.  Auto-Detection Limitations  . . . . . . . . . . . . .  12
       6.3.3.  Example Request . . . . . . . . . . . . . . . . . . .  12
       6.3.4.  Example Response  . . . . . . . . . . . . . . . . . .  12
       6.3.5.  Auto-Detection Failure Response . . . . . . . . . . .  13
     6.4.  Bulk Update Endpoint (/bulk-update) . . . . . . . . . . .  13
       6.4.1.  Example Request . . . . . . . . . . . . . . . . . . .  13
       6.4.2.  Example Response  . . . . . . . . . . . . . . . . . .  13
     6.5.  Status Endpoint (/status/{hostname})  . . . . . . . . . .  14
       6.5.1.  Example Response  . . . . . . . . . . . . . . . . . .  14
     6.6.  Domains Endpoint (/domains) . . . . . . . . . . . . . . .  14
       6.6.1.  Example Response  . . . . . . . . . . . . . . . . . .  15
     6.7.  TXT Record Endpoint (/txt)  . . . . . . . . . . . . . . .  15
       6.7.1.  Design Rationale  . . . . . . . . . . . . . . . . . .  15
       6.7.2.  Set TXT Record (POST) . . . . . . . . . . . . . . . .  15
       6.7.3.  Delete TXT Record (DELETE)  . . . . . . . . . . . . .  16



Ferro                     Expires 21 July 2026                  [Page 2]

Internet-Draft             ApertoDNS Protocol               January 2026


       6.7.4.  Get TXT Records (GET) . . . . . . . . . . . . . . . .  17
   7.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .  18
     7.1.  HTTP Status Codes . . . . . . . . . . . . . . . . . . . .  18
     7.2.  Error Response Format . . . . . . . . . . . . . . . . . .  18
     7.3.  Standard Error Codes  . . . . . . . . . . . . . . . . . .  19
     7.4.  Rate Limiting Headers . . . . . . . . . . . . . . . . . .  20
   8.  Legacy Compatibility  . . . . . . . . . . . . . . . . . . . .  20
     8.1.  Legacy Response Codes . . . . . . . . . . . . . . . . . .  20
   9.  Comparison with RFC 2136  . . . . . . . . . . . . . . . . . .  21
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  21
     10.1.  Transport Security . . . . . . . . . . . . . . . . . . .  21
     10.2.  Token Security . . . . . . . . . . . . . . . . . . . . .  21
     10.3.  Hostname Validation  . . . . . . . . . . . . . . . . . .  22
     10.4.  Rate Limiting  . . . . . . . . . . . . . . . . . . . . .  22
     10.5.  DNS Rebinding Prevention . . . . . . . . . . . . . . . .  22
     10.6.  Input Validation . . . . . . . . . . . . . . . . . . . .  22
     10.7.  TXT Record Abuse Prevention  . . . . . . . . . . . . . .  22
     10.8.  Internationalized Domain Names . . . . . . . . . . . . .  23
   11. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  23
     11.1.  Data Minimization  . . . . . . . . . . . . . . . . . . .  24
     11.2.  User Control . . . . . . . . . . . . . . . . . . . . . .  24
     11.3.  Traffic Analysis . . . . . . . . . . . . . . . . . . . .  24
     11.4.  Encryption . . . . . . . . . . . . . . . . . . . . . . .  24
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  24
     12.1.  Well-Known URI Registration  . . . . . . . . . . . . . .  24
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     13.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  26
   Appendix B.  Implementation Status  . . . . . . . . . . . . . . .  26
     B.1.  ApertoDNS . . . . . . . . . . . . . . . . . . . . . . . .  26
   Appendix C.  OpenAPI Specification  . . . . . . . . . . . . . . .  27
   Appendix D.  Example Update Flow  . . . . . . . . . . . . . . . .  27
   Appendix E.  Changes from Legacy DDNS Protocols . . . . . . . . .  27
   Appendix F.  Changes from -00 . . . . . . . . . . . . . . . . . .  28
     F.1.  Version 1.2.3 Changes . . . . . . . . . . . . . . . . . .  28
     F.2.  Version 1.3.0 Changes (TXT Records) . . . . . . . . . . .  28
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  29

1.  Introduction

   Dynamic DNS (DDNS) services allow users with dynamically assigned IP
   addresses to maintain a consistent hostname that automatically
   updates when their IP address changes.  This capability is essential
   for home users, small businesses, and IoT devices that need to be
   reachable despite lacking static IP addresses.





Ferro                     Expires 21 July 2026                  [Page 3]

Internet-Draft             ApertoDNS Protocol               January 2026


   While RFC 2136 [RFC2136] defines DNS UPDATE for programmatic DNS
   modifications, most consumer-facing DDNS services use simpler HTTP-
   based protocols.  The de facto standard for consumer DDNS emerged
   organically without formal specification.

   This lack of standardization has led to:

   *  Inconsistent implementations across providers

   *  Security vulnerabilities from ad-hoc designs

   *  Limited feature sets (e.g., no native IPv6 support)

   *  Vendor lock-in due to proprietary extensions

   *  No formal capability negotiation

   This document specifies the ApertoDNS Protocol as a modern, secure,
   and fully interoperable alternative designed for the current Internet
   landscape.

1.1.  Protocol Versioning

   The protocol version specified in discovery responses (e.g., "1.3.0")
   refers to the semantic version of the protocol specification itself.
   This document represents the first IETF standardization of a protocol
   that has been in production use since 2024.  The version number in
   the discovery endpoint reflects the feature set available, while the
   Internet-Draft version (e.g., "-01") tracks the IETF document
   revision process separately.

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.3.  Goals

   The ApertoDNS Protocol is designed with the following goals:

   *  *Provider-agnostic*: Any DDNS provider can implement this protocol
      using their own domain and branding

   *  *Secure by default*: HTTPS required, bearer token authentication




Ferro                     Expires 21 July 2026                  [Page 4]

Internet-Draft             ApertoDNS Protocol               January 2026


   *  *Modern*: JSON responses, proper HTTP semantics, native IPv6

   *  *Discoverable*: Self-describing via discovery endpoint

   *  *Extensible*: Capability negotiation allows future enhancements

   *  *Backward compatible*: Optional legacy endpoint for existing
      clients

2.  Terminology

   This document uses the following terms:

   DDNS:  Dynamic DNS.  A service that automatically updates DNS records
      when a client's IP address changes.

   Provider:  An organization or service implementing this protocol to
      offer DDNS services to users.

   Hostname:  A fully qualified domain name (FQDN) managed by the
      provider and associated with a user account.

   Token:  An authentication credential issued by the provider, used to
      authorize API requests.

   Auto-detection:  Server-side determination of the client's IP address
      from the incoming HTTP request, used when the client specifies
      "auto" as the IP value.

   Client:  Software or device that makes requests to a DDNS provider to
      update DNS records.

   A-label:  The ASCII-Compatible Encoding (ACE) form of an
      Internationalized Domain Name label, as defined in [RFC5891].

   TXT Record:  A DNS resource record type used to store arbitrary text
      data, commonly used for domain verification and ACME DNS-01
      challenges.

   ACME DNS-01:  A challenge type defined in [RFC8555] where domain
      ownership is proven by provisioning a DNS TXT record.

3.  Protocol Overview

   The ApertoDNS Protocol is a RESTful API using JSON over HTTPS.  All
   protocol endpoints are located under the well-known URI path /.well-
   known/apertodns/v1/.




Ferro                     Expires 21 July 2026                  [Page 5]

Internet-Draft             ApertoDNS Protocol               January 2026


3.1.  Base URL

   Conforming implementations MUST serve all endpoints under:

   https://{provider-domain}/.well-known/apertodns/v1/

   The use of well-known URIs [RFC8615] ensures consistent endpoint
   discovery across providers.

3.2.  Content Type

   All request and response bodies MUST use the application/json media
   type [RFC8259] unless otherwise specified.

3.3.  Response Format

   All responses MUST include a boolean success field at the top level:

   {
     "success": true,
     "data": { ... }
   }

   Or for errors:

   {
     "success": false,
     "error": {
       "code": "error_code",
       "message": "Human-readable description"
     }
   }

4.  Conformance Requirements

   This section defines the requirements for conforming implementations.

4.1.  Conformance Levels

   This protocol defines two conformance levels:

   Core Conformance:  A conforming implementation MUST implement the
      following endpoints: /info, /health, and /update.  A conforming
      implementation MUST support bearer token authentication.  A
      conforming implementation MUST serve all endpoints over HTTPS.

   Full Conformance:  In addition to core conformance requirements, a




Ferro                     Expires 21 July 2026                  [Page 6]

Internet-Draft             ApertoDNS Protocol               January 2026


      fully conforming implementation MUST implement: /bulk-update,
      /status/{hostname}, and /domains endpoints.

4.2.  Capability Advertisement

   Implementations MUST accurately advertise their capabilities in the
   /info endpoint response.  Implementations MUST NOT advertise
   capabilities they do not support.

4.3.  Interoperability

   Implementations SHOULD accept requests from any conforming client.
   Implementations MUST NOT require proprietary extensions for basic
   DDNS functionality.

5.  Authentication

5.1.  Supported Methods

   Protected endpoints require authentication via one of the following
   methods:

   1.  *Bearer Token* (RECOMMENDED) [RFC6750]: Authorization: Bearer
       {token}

   2.  *API Key Header*: X-API-Key: {token}

   3.  *HTTP Basic* (legacy only): Authorization: Basic {credentials}

   Implementations MUST support bearer token authentication.
   Implementations MAY support additional methods.

5.2.  Token Format

   Tokens SHOULD follow the format:

   {provider}_{environment}_{random}

   Where:

   *  {provider}: Provider identifier (e.g., "apertodns", "example")

   *  {environment}: Token environment ("live", "test", "sandbox")

   *  {random}: Cryptographically secure random string (minimum 32
      characters recommended)

   Example: apertodns_live_Kj8mP2xL9nQ4wR7vY1zA3bC6dE0fG5hI



Ferro                     Expires 21 July 2026                  [Page 7]

Internet-Draft             ApertoDNS Protocol               January 2026


   This format enables:

   *  Easy identification of token source during debugging

   *  Environment separation (production vs. testing)

   *  Consistent token handling across providers

5.3.  Token Transmission

   Tokens MUST be transmitted only in HTTP headers.  Tokens MUST NOT
   appear in URLs, query parameters, or request bodies where they might
   be logged.

6.  Endpoints

6.1.  Discovery Endpoint (/info)

   GET /.well-known/apertodns/v1/info

   The discovery endpoint returns provider information, capabilities,
   and configuration.  This endpoint MUST NOT require authentication.

6.1.1.  Response Fields

      +==================+========+==========+=====================+
      | Field            | Type   | Required | Description         |
      +==================+========+==========+=====================+
      | protocol         | string | YES      | MUST be "apertodns" |
      +------------------+--------+----------+---------------------+
      | protocol_version | string | YES      | Semantic version    |
      |                  |        |          | (e.g., "1.3.0")     |
      +------------------+--------+----------+---------------------+
      | provider         | object | YES      | Provider            |
      |                  |        |          | information         |
      +------------------+--------+----------+---------------------+
      | capabilities     | object | YES      | Supported features  |
      +------------------+--------+----------+---------------------+
      | authentication   | object | YES      | Supported auth      |
      |                  |        |          | methods             |
      +------------------+--------+----------+---------------------+
      | endpoints        | object | YES      | Available endpoint  |
      |                  |        |          | paths               |
      +------------------+--------+----------+---------------------+
      | rate_limits      | object | NO       | Rate limiting       |
      |                  |        |          | configuration       |
      +------------------+--------+----------+---------------------+
      | server_time      | string | NO       | Current server time |



Ferro                     Expires 21 July 2026                  [Page 8]

Internet-Draft             ApertoDNS Protocol               January 2026


      |                  |        |          | (ISO 8601)          |
      +------------------+--------+----------+---------------------+

                                 Table 1

6.1.2.  Capability Fields

   The capabilities object MUST include the following fields:

   +===================+=========+====================================+
   | Field             | Type    | Description                        |
   +===================+=========+====================================+
   | ipv4              | boolean | IPv4 address updates supported     |
   +-------------------+---------+------------------------------------+
   | ipv6              | boolean | IPv6 address updates supported     |
   +-------------------+---------+------------------------------------+
   | auto_ip_detection | boolean | Automatic IP detection supported   |
   +-------------------+---------+------------------------------------+
   | bulk_update       | boolean | Bulk update endpoint available     |
   +-------------------+---------+------------------------------------+
   | max_bulk_size     | integer | Maximum hostnames per bulk request |
   +-------------------+---------+------------------------------------+

                                 Table 2

   The capabilities object MAY include the following OPTIONAL fields:

         +=================+=========+===========================+
         | Field           | Type    | Description               |
         +=================+=========+===========================+
         | webhooks        | boolean | Provider-specific webhook |
         |                 |         | support available         |
         +-----------------+---------+---------------------------+
         | txt_records     | boolean | TXT record management     |
         |                 |         | supported                 |
         +-----------------+---------+---------------------------+
         | txt_max_records | integer | Maximum TXT records per   |
         |                 |         | hostname (default: 5)     |
         +-----------------+---------+---------------------------+

                                  Table 3

   When webhooks is true, the provider offers webhook notifications for
   DNS update events such as IP address changes.  The webhook API is
   implementation-specific and not standardized by this protocol
   version.  Providers offering webhooks SHOULD document their webhook
   API separately.




Ferro                     Expires 21 July 2026                  [Page 9]

Internet-Draft             ApertoDNS Protocol               January 2026


   When txt_records is true, the provider supports TXT record management
   via the /txt endpoint.  This capability enables ACME DNS-01
   challenges [RFC8555] for automated certificate issuance.

   The capabilities object MAY include additional fields for future
   extensions.  Unknown capability fields SHOULD be ignored by clients.

6.1.3.  Example Response

   {
     "success": true,
     "data": {
       "protocol": "apertodns",
       "protocol_version": "1.3.0",
       "provider": {
         "name": "Example DDNS",
         "website": "https://example.com",
         "documentation": "https://example.com/docs",
         "support_email": "support@example.com"
       },
       "capabilities": {
         "ipv4": true,
         "ipv6": true,
         "auto_ip_detection": true,
         "bulk_update": true,
         "webhooks": true,
         "max_bulk_size": 100
       },
       "authentication": {
         "methods": ["bearer_token", "api_key_header"],
         "token_format": "{provider}_{environment}_{random}"
       },
       "endpoints": {
         "info": "/.well-known/apertodns/v1/info",
         "health": "/.well-known/apertodns/v1/health",
         "update": "/.well-known/apertodns/v1/update",
         "bulk_update": "/.well-known/apertodns/v1/bulk-update",
         "status": "/.well-known/apertodns/v1/status/{hostname}",
         "domains": "/.well-known/apertodns/v1/domains"
       },
       "rate_limits": {
         "update": {"requests": 60, "window_seconds": 60},
         "bulk_update": {"requests": 10, "window_seconds": 60}
       },
       "server_time": "2025-01-01T12:00:00.000Z"
     }
   }




Ferro                     Expires 21 July 2026                 [Page 10]

Internet-Draft             ApertoDNS Protocol               January 2026


6.2.  Health Endpoint (/health)

   GET /.well-known/apertodns/v1/health

   Returns service health status.  This endpoint MUST NOT require
   authentication and SHOULD be used for monitoring.

6.2.1.  Example Response

   {
     "success": true,
     "data": {
       "status": "healthy",
       "timestamp": "2025-01-01T12:00:00.000Z"
     }
   }

   The status field MUST be one of: "healthy", "degraded", or
   "unhealthy".

6.3.  Update Endpoint (/update)

   POST /.well-known/apertodns/v1/update
   Authorization: Bearer {token}
   Content-Type: application/json

   Updates DNS records for a single hostname.  This endpoint MUST
   require authentication.

6.3.1.  Request Fields

      +==========+=========+==========+=============================+
      | Field    | Type    | Required | Description                 |
      +==========+=========+==========+=============================+
      | hostname | string  | YES      | Fully qualified domain name |
      +----------+---------+----------+-----------------------------+
      | ipv4     | string  | NO       | IPv4 address or "auto"      |
      +----------+---------+----------+-----------------------------+
      | ipv6     | string  | NO       | IPv6 address or "auto"      |
      +----------+---------+----------+-----------------------------+
      | ttl      | integer | NO       | Time to live in seconds     |
      |          |         |          | (60-86400)                  |
      +----------+---------+----------+-----------------------------+

                                  Table 4

   At least one of ipv4 or ipv6 SHOULD be provided.  If neither is
   provided, implementations SHOULD use auto-detection for IPv4.



Ferro                     Expires 21 July 2026                 [Page 11]

Internet-Draft             ApertoDNS Protocol               January 2026


   The special value "auto" instructs the server to detect the client's
   IP address from the incoming request.

6.3.2.  Auto-Detection Limitations

   Auto-detection is constrained by HTTP connection semantics: the
   server can only detect the address family used by the client's TCP
   connection.  This is a fundamental characteristic of HTTP-based
   protocols, not a limitation specific to this specification.

   The following constraints apply:

   *  If the client connects via IPv4: only IPv4 can be auto-detected

   *  If the client connects via IPv6: only IPv6 can be auto-detected

   *  Cross-family detection is not possible (e.g., detecting IPv4
      address when connected via IPv6)

   When a client requests auto-detection for an address family that does
   not match the connection's address family, the server MUST return an
   error with the appropriate error code (ipv4_auto_failed or
   ipv6_auto_failed).

   Clients requiring dual-stack updates (both IPv4 and IPv6) SHOULD use
   one of the following approaches:

   1.  Provide explicit IP addresses for both fields

   2.  Make separate update requests over each address family

   3.  Use auto-detection for the matching address family and provide an
       explicit address for the other

6.3.3.  Example Request

   {
     "hostname": "home.example.com",
     "ipv4": "auto",
     "ttl": 300
   }

6.3.4.  Example Response








Ferro                     Expires 21 July 2026                 [Page 12]

Internet-Draft             ApertoDNS Protocol               January 2026


   {
     "success": true,
     "data": {
       "hostname": "home.example.com",
       "ipv4": "203.0.113.50",
       "previous_ipv4": "203.0.113.49",
       "ttl": 300,
       "changed": true,
       "timestamp": "2025-01-01T12:00:00.000Z"
     }
   }

   The changed field indicates whether the IP address was actually
   modified (false if the new IP matches the existing record).

6.3.5.  Auto-Detection Failure Response

   When auto-detection fails due to address family mismatch:

   {
     "success": false,
     "error": {
       "code": "ipv4_auto_failed",
       "message": "Cannot auto-detect IPv4 from IPv6 connection"
     }
   }

6.4.  Bulk Update Endpoint (/bulk-update)

   POST /.well-known/apertodns/v1/bulk-update
   Authorization: Bearer {token}
   Content-Type: application/json

   Updates multiple hostnames in a single request.  Providers
   advertising bulk_update: true in capabilities MUST implement this
   endpoint.

6.4.1.  Example Request

   {
     "updates": [
       {"hostname": "home.example.com", "ipv4": "auto"},
       {"hostname": "office.example.com", "ipv4": "203.0.113.51"}
     ]
   }

6.4.2.  Example Response




Ferro                     Expires 21 July 2026                 [Page 13]

Internet-Draft             ApertoDNS Protocol               January 2026


   {
     "success": true,
     "data": {
       "summary": {
         "total": 2,
         "successful": 2,
         "failed": 0
       },
       "results": [
         {
           "hostname": "home.example.com",
           "success": true,
           "ipv4": "203.0.113.50",
           "changed": true
         },
         {
           "hostname": "office.example.com",
           "success": true,
           "ipv4": "203.0.113.51",
           "changed": true
         }
       ]
     }
   }

6.5.  Status Endpoint (/status/{hostname})

   GET /.well-known/apertodns/v1/status/{hostname}
   Authorization: Bearer {token}

   Returns current DNS record status for a hostname.

6.5.1.  Example Response

   {
     "success": true,
     "data": {
       "hostname": "home.example.com",
       "ipv4": "203.0.113.50",
       "ipv6": "2001:db8::1",
       "ttl": 300,
       "last_updated": "2025-01-01T12:00:00.000Z"
     }
   }

6.6.  Domains Endpoint (/domains)





Ferro                     Expires 21 July 2026                 [Page 14]

Internet-Draft             ApertoDNS Protocol               January 2026


   GET /.well-known/apertodns/v1/domains
   Authorization: Bearer {token}

   Returns list of domains and hostnames available to the authenticated
   user.

6.6.1.  Example Response

   {
     "success": true,
     "data": {
       "domains": [
         {
           "domain": "example.com",
           "hostnames": ["home.example.com", "office.example.com"]
         }
       ]
     }
   }

6.7.  TXT Record Endpoint (/txt)

   The TXT record endpoint enables management of DNS TXT records,
   primarily for ACME DNS-01 challenges [RFC8555] used in automated
   certificate issuance.  Providers advertising txt_records: true in
   capabilities MUST implement this endpoint.

6.7.1.  Design Rationale

   TXT record management is designed to support wildcard certificate
   issuance, which requires multiple simultaneous TXT records during the
   ACME validation process.  The protocol supports:

   *  *Accumulation*: Multiple TXT values can coexist for the same
      hostname prefix (e.g., _acme-challenge.example.com)

   *  *Selective deletion*: Individual TXT values can be removed without
      affecting others

   *  *Automatic cleanup*: Providers MAY implement TTL-based expiration
      for TXT records

6.7.2.  Set TXT Record (POST)

   POST /.well-known/apertodns/v1/txt
   Authorization: Bearer {token}
   Content-Type: application/json




Ferro                     Expires 21 July 2026                 [Page 15]

Internet-Draft             ApertoDNS Protocol               January 2026


   Creates or adds a TXT record value for the specified hostname.
   Multiple calls with different values MUST accumulate (not replace)
   TXT records for the same hostname, up to the provider's limit.

6.7.2.1.  Request Fields

   +==========+=========+==========+==================================+
   | Field    | Type    | Required | Description                      |
   +==========+=========+==========+==================================+
   | hostname | string  | YES      | FQDN for the TXT record          |
   +----------+---------+----------+----------------------------------+
   | value    | string  | YES      | TXT record value (max 255 chars) |
   +----------+---------+----------+----------------------------------+
   | ttl      | integer | NO       | Time to live in seconds          |
   |          |         |          | (default: 60)                    |
   +----------+---------+----------+----------------------------------+

                                 Table 5

6.7.2.2.  Example Request

   {
     "hostname": "_acme-challenge.home.example.com",
     "value": "gfj9Xq...Rg85nM",
     "ttl": 60
   }

6.7.2.3.  Example Response

   {
     "success": true,
     "data": {
       "hostname": "_acme-challenge.home.example.com",
       "value": "gfj9Xq...Rg85nM",
       "ttl": 60,
       "record_count": 1,
       "timestamp": "2026-01-01T12:00:00.000Z"
     }
   }

   The record_count field indicates the total number of TXT values
   currently stored for this hostname after the operation.

6.7.3.  Delete TXT Record (DELETE)

   DELETE /.well-known/apertodns/v1/txt
   Authorization: Bearer {token}
   Content-Type: application/json



Ferro                     Expires 21 July 2026                 [Page 16]

Internet-Draft             ApertoDNS Protocol               January 2026


   Removes a specific TXT record value.  If value is omitted, ALL TXT
   records for the hostname are removed.

6.7.3.1.  Request Fields

        +==========+========+==========+==========================+
        | Field    | Type   | Required | Description              |
        +==========+========+==========+==========================+
        | hostname | string | YES      | FQDN of the TXT record   |
        +----------+--------+----------+--------------------------+
        | value    | string | NO       | Specific value to delete |
        |          |        |          | (omit to delete all)     |
        +----------+--------+----------+--------------------------+

                                  Table 6

6.7.3.2.  Example Request (selective deletion)

   {
     "hostname": "_acme-challenge.home.example.com",
     "value": "gfj9Xq...Rg85nM"
   }

6.7.3.3.  Example Response

   {
     "success": true,
     "data": {
       "hostname": "_acme-challenge.home.example.com",
       "deleted": true,
       "values_removed": 1,
       "remaining_count": 1,
       "timestamp": "2026-01-01T12:00:00.000Z"
     }
   }

6.7.4.  Get TXT Records (GET)

   GET /.well-known/apertodns/v1/txt/{hostname}
   Authorization: Bearer {token}

   Returns all TXT record values for a hostname.

6.7.4.1.  Example Response







Ferro                     Expires 21 July 2026                 [Page 17]

Internet-Draft             ApertoDNS Protocol               January 2026


   {
     "success": true,
     "data": {
       "hostname": "_acme-challenge.home.example.com",
       "values": [
         "gfj9Xq...Rg85nM",
         "hK7pLm...Yt42xQ"
       ],
       "ttl": 60,
       "record_count": 2
     }
   }

7.  Error Handling

7.1.  HTTP Status Codes

   Implementations MUST use appropriate HTTP status codes as defined in
   [RFC9110]:

          +========+============================================+
          | Status | Usage                                      |
          +========+============================================+
          | 200    | Successful request                         |
          +--------+--------------------------------------------+
          | 400    | Invalid request (bad hostname, invalid IP) |
          +--------+--------------------------------------------+
          | 401    | Missing or invalid authentication          |
          +--------+--------------------------------------------+
          | 403    | Not authorized for requested resource      |
          +--------+--------------------------------------------+
          | 404    | Resource not found                         |
          +--------+--------------------------------------------+
          | 429    | Rate limit exceeded                        |
          +--------+--------------------------------------------+
          | 500    | Server error                               |
          +--------+--------------------------------------------+

                                  Table 7

7.2.  Error Response Format










Ferro                     Expires 21 July 2026                 [Page 18]

Internet-Draft             ApertoDNS Protocol               January 2026


   {
     "success": false,
     "error": {
       "code": "error_code",
       "message": "Human-readable description"
     }
   }

7.3.  Standard Error Codes

    +====================+=============+=============================+
    | Code               | HTTP Status | Description                 |
    +====================+=============+=============================+
    | unauthorized       | 401         | Missing authentication      |
    +--------------------+-------------+-----------------------------+
    | invalid_token      | 401         | Invalid or expired token    |
    +--------------------+-------------+-----------------------------+
    | forbidden          | 403         | Not authorized for resource |
    +--------------------+-------------+-----------------------------+
    | not_found          | 404         | Hostname not found          |
    +--------------------+-------------+-----------------------------+
    | rate_limited       | 429         | Too many requests           |
    +--------------------+-------------+-----------------------------+
    | invalid_hostname   | 400         | Invalid hostname format     |
    +--------------------+-------------+-----------------------------+
    | invalid_ip         | 400         | Invalid IP address format   |
    +--------------------+-------------+-----------------------------+
    | hostname_not_owned | 403         | User does not own hostname  |
    +--------------------+-------------+-----------------------------+
    | ipv4_auto_failed   | 400         | Cannot auto-detect IPv4     |
    |                    |             | from IPv6 connection        |
    +--------------------+-------------+-----------------------------+
    | ipv6_auto_failed   | 400         | Cannot auto-detect IPv6     |
    |                    |             | from IPv4 connection        |
    +--------------------+-------------+-----------------------------+
    | validation_error   | 400         | Request validation failed   |
    +--------------------+-------------+-----------------------------+
    | invalid_ttl        | 400         | TTL value out of acceptable |
    |                    |             | range                       |
    +--------------------+-------------+-----------------------------+
    | txt_not_supported  | 400         | Provider does not support   |
    |                    |             | TXT records                 |
    +--------------------+-------------+-----------------------------+
    | txt_limit_exceeded | 400         | Maximum TXT records per     |
    |                    |             | hostname exceeded           |
    +--------------------+-------------+-----------------------------+
    | txt_invalid_name   | 400         | TXT hostname must use       |
    |                    |             | allowed prefix              |



Ferro                     Expires 21 July 2026                 [Page 19]

Internet-Draft             ApertoDNS Protocol               January 2026


    +--------------------+-------------+-----------------------------+
    | txt_value_too_long | 400         | TXT value exceeds 255       |
    |                    |             | characters                  |
    +--------------------+-------------+-----------------------------+

                                 Table 8

7.4.  Rate Limiting Headers

   When rate limiting is applied, responses SHOULD include:

   *  Retry-After: Seconds until rate limit resets

   *  X-RateLimit-Limit: Maximum requests per window

   *  X-RateLimit-Remaining: Remaining requests in window

   *  X-RateLimit-Reset: Unix timestamp when window resets

8.  Legacy Compatibility

   For backward compatibility with existing DDNS clients, providers MAY
   implement:

   GET /nic/update?hostname={hostname}&myip={ip}
   Authorization: Basic {credentials}

8.1.  Legacy Response Codes

   Responses MUST be plain text (not JSON):

                  +============+=======================+
                  | Response   | Meaning               |
                  +============+=======================+
                  | good {ip}  | Update successful     |
                  +------------+-----------------------+
                  | nochg {ip} | No change needed      |
                  +------------+-----------------------+
                  | badauth    | Authentication failed |
                  +------------+-----------------------+
                  | notfqdn    | Invalid hostname      |
                  +------------+-----------------------+
                  | nohost     | Hostname not found    |
                  +------------+-----------------------+
                  | abuse      | Account blocked       |
                  +------------+-----------------------+

                                 Table 9



Ferro                     Expires 21 July 2026                 [Page 20]

Internet-Draft             ApertoDNS Protocol               January 2026


   This endpoint is provided for compatibility only.  New
   implementations SHOULD use the modern JSON endpoints.

9.  Comparison with RFC 2136

   RFC 2136 [RFC2136] defines DNS UPDATE, a protocol for dynamic updates
   to DNS zones.  The ApertoDNS Protocol differs in several key aspects:

           +===========+=================+====================+
           | Aspect    | RFC 2136        | ApertoDNS Protocol |
           +===========+=================+====================+
           | Transport | DNS (UDP/TCP)   | HTTPS              |
           +-----------+-----------------+--------------------+
           | Format    | DNS wire format | JSON               |
           +-----------+-----------------+--------------------+
           | Auth      | TSIG/SIG(0)     | Bearer tokens      |
           +-----------+-----------------+--------------------+
           | Discovery | None            | /info endpoint     |
           +-----------+-----------------+--------------------+
           | IPv6      | Supported       | Native support     |
           +-----------+-----------------+--------------------+
           | Bulk ops  | Per-message     | Dedicated endpoint |
           +-----------+-----------------+--------------------+

                                 Table 10

   The ApertoDNS Protocol is designed for consumer DDNS services where
   simplicity and HTTP integration are priorities, while RFC 2136 is
   suited for direct DNS zone manipulation.

10.  Security Considerations

10.1.  Transport Security

   All endpoints MUST be served over HTTPS using TLS 1.2 or higher.
   Implementations MUST NOT support plaintext HTTP for any protocol
   endpoint.

   Implementations SHOULD support TLS 1.3 and SHOULD disable older
   cipher suites known to be weak.

10.2.  Token Security

   *  Tokens MUST be generated using cryptographically secure random
      number generators (CSPRNG)

   *  Tokens SHOULD have configurable expiration




Ferro                     Expires 21 July 2026                 [Page 21]

Internet-Draft             ApertoDNS Protocol               January 2026


   *  Providers SHOULD support token revocation

   *  Tokens MUST NOT be logged in server access logs

   *  Tokens MUST NOT appear in URLs or error messages

10.3.  Hostname Validation

   Before processing any update request, implementations MUST verify
   that the authenticated user owns or has permission to modify the
   requested hostname.  Failure to validate ownership could allow
   unauthorized DNS modifications.

10.4.  Rate Limiting

   Providers SHOULD implement rate limiting to prevent:

   *  Brute-force token guessing

   *  Denial of service attacks

   *  Excessive DNS propagation load

   Rate limits SHOULD be advertised in the discovery endpoint and
   communicated via response headers.

10.5.  DNS Rebinding Prevention

   Implementations MUST validate that IP addresses in update requests
   are not private, loopback, or link-local addresses unless explicitly
   configured to allow such addresses.

10.6.  Input Validation

   All user input MUST be validated:

   *  Hostnames MUST conform to DNS naming rules

   *  IP addresses MUST be valid IPv4 or IPv6 format

   *  TTL values MUST be within acceptable ranges

   *  TXT values MUST NOT exceed 255 characters

10.7.  TXT Record Abuse Prevention

   TXT records can potentially be abused for:




Ferro                     Expires 21 July 2026                 [Page 22]

Internet-Draft             ApertoDNS Protocol               January 2026


   *  *DNS tunneling*: Encoding data in TXT records for covert
      communication

   *  *Data exfiltration*: Using DNS queries to leak sensitive data

   *  *Resource exhaustion*: Creating excessive TXT records

   Implementations MUST implement safeguards:

   *  Limit TXT value length to 255 characters (DNS standard)

   *  Limit number of TXT records per hostname (default: 5)

   *  Restrict TXT hostnames to approved prefixes (e.g., _acme-
      challenge.)

   *  Implement rate limiting on TXT operations

   *  Consider automatic expiration of TXT records (recommended: 24
      hours)

10.8.  Internationalized Domain Names

   When handling Internationalized Domain Names (IDNs), the following
   requirements apply as specified in [RFC5891]:

   *  Clients SHOULD convert IDN hostnames to their A-label (ASCII
      Compatible Encoding) form before sending requests

   *  Servers MUST accept hostnames in A-label form

   *  Servers MAY accept hostnames in U-label (Unicode) form and convert
      them to A-labels internally

   *  Servers MUST store and return hostnames in a consistent form

   For example, a client wishing to update the hostname "例え.example.com"
   SHOULD send the request with the A-label form "xn--
   r8jz45g.example.com".

   Implementations that accept U-label input MUST perform IDNA2008
   validation as specified in [RFC5891] before processing the request.

11.  Privacy Considerations

   This section addresses privacy considerations as recommended by
   [RFC6973].




Ferro                     Expires 21 July 2026                 [Page 23]

Internet-Draft             ApertoDNS Protocol               January 2026


11.1.  Data Minimization

   Providers SHOULD minimize the collection and retention of personal
   data.  Specifically:

   *  IP address history SHOULD have configurable retention periods

   *  Update timestamps MAY be retained for operational purposes

   *  Providers SHOULD document their data retention policies

11.2.  User Control

   Users SHOULD have mechanisms to:

   *  View their stored data

   *  Delete their accounts and associated data

   *  Export their data in a portable format

11.3.  Traffic Analysis

   DDNS updates inherently reveal:

   *  That a user's IP address has changed

   *  The timing of IP address changes

   *  The association between a hostname and IP address

   Providers should be aware that this information could be used to
   track user behavior or network changes.

11.4.  Encryption

   All communications MUST be encrypted via HTTPS, preventing passive
   observation of update requests and tokens.

12.  IANA Considerations

12.1.  Well-Known URI Registration

   This document requests registration of the following well-known URI
   suffix:

   URI Suffix:  apertodns




Ferro                     Expires 21 July 2026                 [Page 24]

Internet-Draft             ApertoDNS Protocol               January 2026


   Change Controller:  IETF

   Specification Document:  This document

   Related Information:  None

   The well-known URI /.well-known/apertodns/ is used as the base path
   for all protocol endpoints.

13.  References

13.1.  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/rfc/rfc2119>.

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891,
              DOI 10.17487/RFC5891, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5891>.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <https://www.rfc-editor.org/rfc/rfc6750>.

   [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/rfc/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8259>.

   [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/rfc/rfc8555>.

   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
              <https://www.rfc-editor.org/rfc/rfc8615>.






Ferro                     Expires 21 July 2026                 [Page 25]

Internet-Draft             ApertoDNS Protocol               January 2026


   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9110>.

13.2.  Informative References

   [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/rfc/rfc2136>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,
              <https://www.rfc-editor.org/rfc/rfc6973>.

Appendix A.  Acknowledgments

   Thanks to the dynamic DNS community for decades of service enabling
   home users and small businesses to maintain stable hostnames with
   dynamic IP addresses.

   Thanks to the IETF DNSOP working group participants for their review
   and feedback on this specification.

Appendix B.  Implementation Status

   Note to RFC Editor: Please remove this appendix before publication.

   This section records the status of known implementations of the
   protocol defined by this specification.

B.1.  ApertoDNS

   Organization:  ApertoDNS

   Implementation:  Reference implementation

   Description:  Full protocol support including all endpoints, bulk
      updates, webhooks, and legacy compatibility

   Level of Maturity:  Production

   Coverage:  Complete

   Licensing:  Proprietary service, open protocol



Ferro                     Expires 21 July 2026                 [Page 26]

Internet-Draft             ApertoDNS Protocol               January 2026


   Contact:  support@apertodns.com

   URL:  https://apertodns.com

Appendix C.  OpenAPI Specification

   A complete OpenAPI 3.0.3 specification for this protocol is available
   at:

   https://github.com/apertodns/apertodns-protocol/blob/main/
   openapi.yaml

   This specification can be used to:

   *  Generate client libraries in various programming languages

   *  Create interactive API documentation

   *  Validate implementations for conformance

Appendix D.  Example Update Flow

   The following illustrates a typical update flow:

   1.  Client discovers provider capabilities: ~~~ GET /.well-
       known/apertodns/v1/info ~~~

   2.  Client authenticates and requests update: ~~~ POST /.well-
       known/apertodns/v1/update Authorization: Bearer
       example_live_abc123 Content-Type: application/json

       {"hostname": "home.example.com", "ipv4": "auto"} ~~~

   3.  Provider validates token and hostname ownership

   4.  Provider updates DNS record

   5.  Provider returns result: ~~~json { "success": true, "data": {
       "hostname": "home.example.com", "ipv4": "203.0.113.50",
       "changed": true } } ~~~

   6.  DNS propagates the new record

Appendix E.  Changes from Legacy DDNS Protocols

   For implementers familiar with legacy HTTP-based DDNS protocols
   (commonly referred to as "dyndns2" in client implementations such as
   ddclient), key differences include:



Ferro                     Expires 21 July 2026                 [Page 27]

Internet-Draft             ApertoDNS Protocol               January 2026


   *  JSON responses instead of plain text

   *  Bearer token authentication instead of HTTP Basic

   *  Explicit capability negotiation via /info endpoint

   *  Dedicated endpoints for different operations

   *  Standardized error codes and response formats

   *  Native IPv6 support with separate fields

   *  Bulk update support for multiple hostnames

   *  Well-known URI path for consistent discovery

Appendix F.  Changes from -00

   This section summarizes changes from draft-ferro-dnsop-apertodns-
   protocol-00:

F.1.  Version 1.2.3 Changes

   *  Added ipv4_auto_failed and ipv6_auto_failed error codes to
      Section 8.3 (Standard Error Codes)

   *  Added "Auto-Detection Limitations" subsection to Section 7.3
      (Update Endpoint) documenting HTTP connection semantics
      constraints

   *  Added validation_error and invalid_ttl error codes

   *  Added example response for auto-detection failure

   *  Updated protocol version in examples from "1.2.0" to "1.3.0"

   *  Added acknowledgment of IETF DNSOP working group

F.2.  Version 1.3.0 Changes (TXT Records)

   *  Added TXT record management endpoint (/txt) for ACME DNS-01
      challenges

   *  Added txt_records and txt_max_records capability fields

   *  Added TXT-related error codes: txt_not_supported,
      txt_limit_exceeded, txt_invalid_name, txt_value_too_long




Ferro                     Expires 21 July 2026                 [Page 28]

Internet-Draft             ApertoDNS Protocol               January 2026


   *  Added "TXT Record Abuse Prevention" section to Security
      Considerations

   *  Added RFC 8555 (ACME) to normative references

   *  Added TXT Record and ACME DNS-01 terminology definitions

   *  Updated protocol version to 1.3.0

Author's Address

   Andrea Ferro
   ApertoDNS
   Italy
   Email: support@apertodns.com




































Ferro                     Expires 21 July 2026                 [Page 29]
