DNS Operations A. Ferro Internet-Draft ApertoDNS Intended status: Standards Track 22 January 2026 Expires: 26 July 2026 ApertoDNS Protocol: A Modern Dynamic DNS Update Protocol draft-ferro-dnsop-apertodns-protocol-02 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 26 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 26 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 . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Protocol Versioning . . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Base URL . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Content Type . . . . . . . . . . . . . . . . . . . . . . 6 3.3. Response Format . . . . . . . . . . . . . . . . . . . . . 6 4. Conformance Requirements . . . . . . . . . . . . . . . . . . 7 4.1. Conformance Levels . . . . . . . . . . . . . . . . . . . 7 4.2. Capability Advertisement . . . . . . . . . . . . . . . . 7 4.3. Interoperability . . . . . . . . . . . . . . . . . . . . 7 5. Authentication . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Supported Methods . . . . . . . . . . . . . . . . . . . . 7 5.2. Token Format . . . . . . . . . . . . . . . . . . . . . . 8 5.3. Token Transmission . . . . . . . . . . . . . . . . . . . 8 5.4. Authorization Scopes . . . . . . . . . . . . . . . . . . 8 6. Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Discovery Endpoint (/info) . . . . . . . . . . . . . . . 9 6.1.1. Response Fields . . . . . . . . . . . . . . . . . . . 9 6.1.2. Capability Fields . . . . . . . . . . . . . . . . . . 10 6.1.3. Example Response . . . . . . . . . . . . . . . . . . 11 6.2. Health Endpoint (/health) . . . . . . . . . . . . . . . . 13 6.2.1. Example Response . . . . . . . . . . . . . . . . . . 13 6.3. Update Endpoint (/update) . . . . . . . . . . . . . . . . 13 6.3.1. Request Fields . . . . . . . . . . . . . . . . . . . 13 6.3.2. Auto-Detection Limitations . . . . . . . . . . . . . 14 6.3.3. Example Request . . . . . . . . . . . . . . . . . . . 14 6.3.4. Example Response . . . . . . . . . . . . . . . . . . 14 6.3.5. Backward Compatibility . . . . . . . . . . . . . . . 15 6.3.6. Auto-Detection Failure Response . . . . . . . . . . . 15 6.3.7. Record Deletion via Null Values . . . . . . . . . . . 15 6.4. Bulk Update Endpoint (/bulk-update) . . . . . . . . . . . 17 6.4.1. Example Request . . . . . . . . . . . . . . . . . . . 17 6.4.2. Example Response . . . . . . . . . . . . . . . . . . 17 6.5. Status Endpoint (/status/{hostname}) . . . . . . . . . . 18 6.5.1. Example Response . . . . . . . . . . . . . . . . . . 18 6.6. Domains Endpoint (/domains) . . . . . . . . . . . . . . . 18 6.6.1. Example Response . . . . . . . . . . . . . . . . . . 19 6.7. TXT Record Endpoint (/txt) . . . . . . . . . . . . . . . 19 Ferro Expires 26 July 2026 [Page 2] Internet-Draft ApertoDNS Protocol January 2026 6.7.1. Design Rationale . . . . . . . . . . . . . . . . . . 19 6.7.2. Set TXT Record (POST) . . . . . . . . . . . . . . . . 20 6.7.3. Delete TXT Record (DELETE) . . . . . . . . . . . . . 21 6.7.4. Get TXT Records (GET) . . . . . . . . . . . . . . . . 22 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 22 7.1. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 22 7.2. Error Response Format . . . . . . . . . . . . . . . . . . 23 7.3. Standard Error Codes . . . . . . . . . . . . . . . . . . 23 7.4. Rate Limiting Headers . . . . . . . . . . . . . . . . . . 24 8. Legacy Compatibility . . . . . . . . . . . . . . . . . . . . 24 8.1. Legacy Response Codes . . . . . . . . . . . . . . . . . . 25 9. Comparison with RFC 2136 . . . . . . . . . . . . . . . . . . 25 10. Concurrency Model . . . . . . . . . . . . . . . . . . . . . . 26 10.1. Last-Write-Wins Semantics . . . . . . . . . . . . . . . 26 10.2. Implications for Clients . . . . . . . . . . . . . . . . 26 10.3. Example Scenario . . . . . . . . . . . . . . . . . . . . 26 10.4. Recommendations for Conflict-Sensitive Applications . . 27 11. Security Considerations . . . . . . . . . . . . . . . . . . . 27 11.1. Transport Security . . . . . . . . . . . . . . . . . . . 27 11.2. Token Security . . . . . . . . . . . . . . . . . . . . . 27 11.3. Hostname Validation . . . . . . . . . . . . . . . . . . 27 11.4. Rate Limiting . . . . . . . . . . . . . . . . . . . . . 28 11.5. IP Address Validation . . . . . . . . . . . . . . . . . 28 11.5.1. Rejected IPv4 Addresses . . . . . . . . . . . . . . 28 11.5.2. Rejected IPv6 Addresses . . . . . . . . . . . . . . 29 11.5.3. Implementation Notes . . . . . . . . . . . . . . . . 30 11.6. Input Validation . . . . . . . . . . . . . . . . . . . . 30 11.7. TXT Record Abuse Prevention . . . . . . . . . . . . . . 31 11.8. Internationalized Domain Names . . . . . . . . . . . . . 31 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 32 12.1. Data Minimization . . . . . . . . . . . . . . . . . . . 32 12.2. User Control . . . . . . . . . . . . . . . . . . . . . . 32 12.3. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 32 12.4. Encryption . . . . . . . . . . . . . . . . . . . . . . . 32 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 13.1. Well-Known URI Registration . . . . . . . . . . . . . . 33 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 14.1. Normative References . . . . . . . . . . . . . . . . . . 33 14.2. Informative References . . . . . . . . . . . . . . . . . 35 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 36 Appendix B. Implementation Status . . . . . . . . . . . . . . . 36 B.1. ApertoDNS . . . . . . . . . . . . . . . . . . . . . . . . 36 Appendix C. OpenAPI Specification . . . . . . . . . . . . . . . 36 Appendix D. Example Update Flow . . . . . . . . . . . . . . . . 37 Appendix E. Changes from Legacy DDNS Protocols . . . . . . . . . 37 Appendix F. Changes from -00 . . . . . . . . . . . . . . . . . . 38 F.1. Version 1.2.3 Changes . . . . . . . . . . . . . . . . . . 38 F.2. Version 1.3.0 Changes (TXT Records) . . . . . . . . . . . 38 Ferro Expires 26 July 2026 [Page 3] Internet-Draft ApertoDNS Protocol January 2026 Appendix G. Changes from -01 . . . . . . . . . . . . . . . . . . 39 G.1. Version 1.3.2 Changes (Response Consistency) . . . . . . 39 G.2. Version 1.3.2 Changes (Enhancements) . . . . . . . . . . 39 G.3. Version 1.4.0 Changes (Record Deletion and Concurrency) . . . . . . . . . . . . . . . . . . . . . . 40 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 40 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. 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., "-02") tracks the IETF document revision process separately. Ferro Expires 26 July 2026 [Page 4] Internet-Draft ApertoDNS Protocol January 2026 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 * *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. Ferro Expires 26 July 2026 [Page 5] Internet-Draft ApertoDNS Protocol January 2026 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/. 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" } } Ferro Expires 26 July 2026 [Page 6] Internet-Draft ApertoDNS Protocol January 2026 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 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. Ferro Expires 26 July 2026 [Page 7] Internet-Draft ApertoDNS Protocol January 2026 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 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. 5.4. Authorization Scopes Servers MAY implement scope-based authorization to limit token permissions. When supported, the /info endpoint SHOULD include a scopes_supported array in the authentication object. The following scopes are defined: Ferro Expires 26 July 2026 [Page 8] Internet-Draft ApertoDNS Protocol January 2026 +==============+=========================================+ | Scope | Description | +==============+=========================================+ | dns:update | Permission to update DNS A/AAAA records | +--------------+-----------------------------------------+ | domains:read | Permission to list user's domains | +--------------+-----------------------------------------+ | txt:read | Permission to read TXT records | +--------------+-----------------------------------------+ | txt:write | Permission to create/update TXT records | +--------------+-----------------------------------------+ | txt:delete | Permission to delete TXT records | +--------------+-----------------------------------------+ Table 1 Tokens with insufficient scope MUST receive a 403 Forbidden response when attempting operations outside their permitted scope. 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 | Ferro Expires 26 July 2026 [Page 9] Internet-Draft ApertoDNS Protocol January 2026 +------------------+--------+----------+---------------------+ | rate_limits | object | NO | Rate limiting | | | | | configuration | +------------------+--------+----------+---------------------+ | server_time | string | NO | Current server time | | | | | (ISO 8601) | +------------------+--------+----------+---------------------+ Table 2 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 3 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 | Max TXT records per | | | | hostname (5) | +-----------------+---------+---------------------------+ Table 4 Ferro Expires 26 July 2026 [Page 10] Internet-Draft ApertoDNS Protocol January 2026 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. 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 Ferro Expires 26 July 2026 [Page 11] Internet-Draft ApertoDNS Protocol January 2026 { "success": true, "data": { "protocol": "apertodns", "protocol_version": "1.4.0", "provider": { "name": "Example DDNS", "website": "https://example.com", "documentation": "https://example.com/docs", "support_email": "support@example.com", "privacy_policy": "https://example.com/privacy", "terms_of_service": "https://example.com/terms" }, "capabilities": { "ipv4": true, "ipv6": true, "auto_ip_detection": true, "bulk_update": true, "webhooks": true, "txt_records": true, "max_bulk_size": 100, "txt_max_records": 5 }, "authentication": { "methods": ["bearer_token", "api_key_header"], "token_format": "{provider}_{environment}_{random}", "scopes_supported": [ "dns:update", "domains:read", "txt:read", "txt:write", "txt:delete" ] }, "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", "txt": "/.well-known/apertodns/v1/txt" }, "rate_limits": { "update": {"requests": 60, "window_seconds": 60}, "bulk_update": {"requests": 10, "window_seconds": 60} }, "server_time": "2026-01-15T12:00:00.000Z" } } Ferro Expires 26 July 2026 [Page 12] 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": "2026-01-15T12:00:00.000Z" } } 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 5 At least one of ipv4 or ipv6 SHOULD be provided. If neither is provided, implementations SHOULD use auto-detection for IPv4. Ferro Expires 26 July 2026 [Page 13] 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 26 July 2026 [Page 14] 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, "updated_at": "2026-01-15T12:00:00.000Z" } } The changed field indicates whether the IP address was actually modified (false if the new IP matches the existing record). 6.3.5. Backward Compatibility For backward compatibility during the transition from legacy field names, servers MAY also include the following deprecated fields in the response: * ipv4_previous: Alias for previous_ipv4 (deprecated) * ipv6_previous: Alias for previous_ipv6 (deprecated) Clients SHOULD use previous_ipv4 and previous_ipv6. The deprecated field names will be removed in a future protocol version. 6.3.6. Auto-Detection Failure Response When auto-detection fails due to address family mismatch: { "success": false, "error": { "code": "ipv4_auto_failed", "message": "Cannot detect IPv4: client connected via IPv6" } } 6.3.7. Record Deletion via Null Values Clients MAY delete specific DNS record types by setting the corresponding field to null in the update request. This enables selective removal of A or AAAA records without affecting other record types. The following semantics apply: Ferro Expires 26 July 2026 [Page 15] Internet-Draft ApertoDNS Protocol January 2026 +=================+==============================+ | Field Value | Server Action | +=================+==============================+ | "203.0.113.1" | Create or update the record | +-----------------+------------------------------+ | "auto" | Auto-detect and update | +-----------------+------------------------------+ | null | Delete the record | +-----------------+------------------------------+ | (field omitted) | No change to existing record | +-----------------+------------------------------+ Table 6 Servers MUST distinguish between an explicit null value (delete request) and an omitted field (no change requested). 6.3.7.1. Example: Delete IPv6 Record Request to delete the AAAA record while preserving the A record: { "hostname": "home.example.com", "ipv6": null } Response: { "success": true, "data": { "hostname": "home.example.com", "ipv4": "203.0.113.50", "ipv6": null, "previous_ipv6": "2001:db8::1", "ttl": 300, "changed": true, "updated_at": "2026-01-21T12:00:00.000Z" } } 6.3.7.2. Example: Delete IPv4 Record Request to delete the A record: Ferro Expires 26 July 2026 [Page 16] Internet-Draft ApertoDNS Protocol January 2026 { "hostname": "home.example.com", "ipv4": null } Response: { "success": true, "data": { "hostname": "home.example.com", "ipv4": null, "ipv6": "2001:db8::1", "previous_ipv4": "203.0.113.50", "ttl": 300, "changed": true, "updated_at": "2026-01-21T12:00:00.000Z" } } When a record is deleted, the corresponding field in the response MUST be null, and the previous_* field MUST contain the value that was deleted. 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 26 July 2026 [Page 17] 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, "updated_at": "2026-01-15T12:00:00.000Z" } } 6.6. Domains Endpoint (/domains) Ferro Expires 26 July 2026 [Page 18] Internet-Draft ApertoDNS Protocol January 2026 GET /.well-known/apertodns/v1/domains Authorization: Bearer {token} Returns list of hostnames available to the authenticated user, with their current DNS record status. The response is a flat array of hostname objects containing full details for each entry. 6.6.1. Example Response { "success": true, "data": [ { "hostname": "home.example.com", "ipv4": "203.0.113.50", "ipv6": "2001:db8::1", "ttl": 300, "updated_at": "2026-01-15T12:00:00.000Z", "created_at": "2024-06-15T08:30:00.000Z" }, { "hostname": "office.example.com", "ipv4": "203.0.113.51", "ipv6": "2001:db8::2", "ttl": 300, "updated_at": "2026-01-15T12:00:00.000Z", "created_at": "2024-06-15T08:35:00.000Z" } ] } 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) Ferro Expires 26 July 2026 [Page 19] Internet-Draft ApertoDNS Protocol January 2026 * *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 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 7 6.7.2.2. Example Request { "hostname": "_acme-challenge.home.example.com", "value": "gfj9Xq...Rg85nM", "ttl": 60 } 6.7.2.3. Example Response Ferro Expires 26 July 2026 [Page 20] Internet-Draft ApertoDNS Protocol January 2026 { "success": true, "data": { "hostname": "_acme-challenge.home.example.com", "value": "gfj9Xq...Rg85nM", "ttl": 60, "record_count": 1, "timestamp": "2026-01-15T12:00:00.000Z" } } 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 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 8 6.7.3.2. Example Request (selective deletion) { "hostname": "_acme-challenge.home.example.com", "value": "gfj9Xq...Rg85nM" } 6.7.3.3. Example Response Ferro Expires 26 July 2026 [Page 21] Internet-Draft ApertoDNS Protocol January 2026 { "success": true, "data": { "hostname": "_acme-challenge.home.example.com", "deleted": true, "values_removed": 1, "remaining_count": 1, "timestamp": "2026-01-15T12:00:00.000Z" } } 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 { "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]: Ferro Expires 26 July 2026 [Page 22] Internet-Draft ApertoDNS Protocol January 2026 +========+============================================+ | 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 9 7.2. Error Response Format { "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 | Ferro Expires 26 July 2026 [Page 23] Internet-Draft ApertoDNS Protocol January 2026 +--------------------+-------------+-----------------------------+ | hostname_not_owned | 403 | User does not own hostname | +--------------------+-------------+-----------------------------+ | ipv4_auto_failed | 400 | Cannot detect IPv4 from | | | | IPv6 connection | +--------------------+-------------+-----------------------------+ | ipv6_auto_failed | 400 | Cannot 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 | +--------------------+-------------+-----------------------------+ | txt_value_too_long | 400 | TXT value exceeds 255 | | | | characters | +--------------------+-------------+-----------------------------+ Table 10 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} Ferro Expires 26 July 2026 [Page 24] Internet-Draft ApertoDNS Protocol January 2026 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 11 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 12 Ferro Expires 26 July 2026 [Page 25] Internet-Draft ApertoDNS Protocol January 2026 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. Concurrency Model This section describes the behavior when multiple clients attempt to update the same hostname concurrently. 10.1. Last-Write-Wins Semantics The protocol uses a last-write-wins model for concurrent updates. When multiple clients update the same hostname: * The most recent update takes precedence * No conflict detection or resolution is performed * The previous_* fields reflect the value immediately before the current update, regardless of which client set it 10.2. Implications for Clients Clients operating in environments where multiple devices may update the same hostname SHOULD be aware of the following: 1. *Update intervals*: Clients SHOULD implement appropriate update intervals to minimize conflicts 2. *Change detection*: Clients MAY compare previous_* values with expected values to detect concurrent modifications 3. *Idempotent updates*: When the new IP matches the existing record, changed will be false regardless of which client originally set the value 10.3. Example Scenario Consider two clients (A and B) updating the same hostname: 1. Initial state: ipv4 = "203.0.113.10" 2. Client A sends update with ipv4 = "203.0.113.20" (succeeds, previous_ipv4 = "203.0.113.10") 3. Client B sends update with ipv4 = "203.0.113.30" (succeeds, previous_ipv4 = "203.0.113.20") Ferro Expires 26 July 2026 [Page 26] Internet-Draft ApertoDNS Protocol January 2026 4. Final state: ipv4 = "203.0.113.30" Client A's update was overwritten by Client B. Neither client receives an error, as this is expected behavior under last-write-wins semantics. 10.4. Recommendations for Conflict-Sensitive Applications Applications requiring stronger consistency guarantees SHOULD: * Use separate hostnames for each client/device * Implement application-level coordination outside this protocol * Consider using RFC 2136 [RFC2136] which supports prerequisite conditions for updates 11. Security Considerations 11.1. 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. 11.2. Token Security * Tokens MUST be generated using cryptographically secure random number generators (CSPRNG) * Tokens SHOULD have configurable expiration * Providers SHOULD support token revocation * Tokens MUST NOT be logged in server access logs * Tokens MUST NOT appear in URLs or error messages 11.3. 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. Ferro Expires 26 July 2026 [Page 27] Internet-Draft ApertoDNS Protocol January 2026 11.4. 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. 11.5. IP Address Validation Implementations MUST reject IP addresses that are not globally routable. This prevents DNS rebinding attacks and ensures that dynamic DNS records point to legitimate public addresses. 11.5.1. Rejected IPv4 Addresses The following IPv4 address ranges MUST be rejected per [RFC6890]: Ferro Expires 26 July 2026 [Page 28] Internet-Draft ApertoDNS Protocol January 2026 +====================+==============================+===========+ | Address Block | Attribute | Reference | +====================+==============================+===========+ | 0.0.0.0/8 | "This network" | [RFC791] | +--------------------+------------------------------+-----------+ | 10.0.0.0/8 | Private-Use | [RFC1918] | +--------------------+------------------------------+-----------+ | 100.64.0.0/10 | Shared Address Space (CGNAT) | [RFC6598] | +--------------------+------------------------------+-----------+ | 127.0.0.0/8 | Loopback | [RFC1122] | +--------------------+------------------------------+-----------+ | 169.254.0.0/16 | Link-Local | [RFC3927] | +--------------------+------------------------------+-----------+ | 172.16.0.0/12 | Private-Use | [RFC1918] | +--------------------+------------------------------+-----------+ | 192.0.0.0/24 | IETF Protocol Assignments | [RFC6890] | +--------------------+------------------------------+-----------+ | 192.0.2.0/24 | Documentation (TEST-NET-1) | [RFC5737] | +--------------------+------------------------------+-----------+ | 192.168.0.0/16 | Private-Use | [RFC1918] | +--------------------+------------------------------+-----------+ | 198.18.0.0/15 | Benchmarking | [RFC2544] | +--------------------+------------------------------+-----------+ | 198.51.100.0/24 | Documentation (TEST-NET-2) | [RFC5737] | +--------------------+------------------------------+-----------+ | 203.0.113.0/24 | Documentation (TEST-NET-3) | [RFC5737] | +--------------------+------------------------------+-----------+ | 224.0.0.0/4 | Multicast | [RFC5771] | +--------------------+------------------------------+-----------+ | 240.0.0.0/4 | Reserved | [RFC1112] | +--------------------+------------------------------+-----------+ | 255.255.255.255/32 | Limited Broadcast | [RFC919] | +--------------------+------------------------------+-----------+ Table 13 11.5.2. Rejected IPv6 Addresses The following IPv6 address ranges MUST be rejected per [RFC6890]: Ferro Expires 26 July 2026 [Page 29] Internet-Draft ApertoDNS Protocol January 2026 +===============+=======================+===========+ | Address Block | Attribute | Reference | +===============+=======================+===========+ | ::/128 | Unspecified | [RFC4291] | +---------------+-----------------------+-----------+ | ::1/128 | Loopback | [RFC4291] | +---------------+-----------------------+-----------+ | ::ffff:0:0/96 | IPv4-mapped | [RFC4291] | +---------------+-----------------------+-----------+ | 64:ff9b::/96 | IPv4-IPv6 Translation | [RFC6052] | +---------------+-----------------------+-----------+ | 100::/64 | Discard-Only | [RFC6666] | +---------------+-----------------------+-----------+ | 2001:db8::/32 | Documentation | [RFC3849] | +---------------+-----------------------+-----------+ | fc00::/7 | Unique Local (ULA) | [RFC4193] | +---------------+-----------------------+-----------+ | fe80::/10 | Link-Local | [RFC4291] | +---------------+-----------------------+-----------+ | ff00::/8 | Multicast | [RFC4291] | +---------------+-----------------------+-----------+ Table 14 11.5.3. Implementation Notes Implementations SHOULD return the invalid_ip error code when rejecting addresses from these ranges. Implementations MAY log rejected addresses for security monitoring purposes. Note: The documentation ranges (192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 for IPv4 and 2001:db8::/32 for IPv6) are used in examples throughout this specification but MUST be rejected in production deployments. Implementations MAY provide configuration options to allow specific private ranges for internal deployments, but such configurations MUST be explicitly enabled and SHOULD generate warnings. 11.6. 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 Ferro Expires 26 July 2026 [Page 30] Internet-Draft ApertoDNS Protocol January 2026 * TXT values MUST NOT exceed 255 characters 11.7. TXT Record Abuse Prevention TXT records can potentially be abused for: * *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) 11.8. 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 an internationalized hostname SHOULD send the request with the A-label form (e.g., "xn-- r8jz45g.example.com" for a Japanese hostname). Implementations that accept U-label input MUST perform IDNA2008 validation as specified in [RFC5891] before processing the request. Ferro Expires 26 July 2026 [Page 31] Internet-Draft ApertoDNS Protocol January 2026 12. Privacy Considerations This section addresses privacy considerations as recommended by [RFC6973]. 12.1. 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 12.2. User Control Users SHOULD have mechanisms to: * View their stored data * Delete their accounts and associated data * Export their data in a portable format 12.3. 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. 12.4. Encryption All communications MUST be encrypted via HTTPS, preventing passive observation of update requests and tokens. 13. IANA Considerations Ferro Expires 26 July 2026 [Page 32] Internet-Draft ApertoDNS Protocol January 2026 13.1. Well-Known URI Registration This document requests registration of the following well-known URI suffix: URI Suffix: apertodns 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. 14. References 14.1. Normative References [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, DOI 10.17487/RFC1112, August 1989, . [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, DOI 10.17487/RFC1122, October 1989, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic Configuration of IPv4 Link-Local Addresses", RFC 3927, DOI 10.17487/RFC3927, May 2005, . [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, . [RFC5771] Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for IPv4 Multicast Address Assignments", BCP 51, RFC 5771, DOI 10.17487/RFC5771, March 2010, . Ferro Expires 26 July 2026 [Page 33] Internet-Draft ApertoDNS Protocol January 2026 [RFC5891] Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, August 2010, . [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, DOI 10.17487/RFC6052, October 2010, . [RFC6598] Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address Space", BCP 153, RFC 6598, DOI 10.17487/RFC6598, April 2012, . [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012, . [RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman, "Special-Purpose IP Address Registries", BCP 153, RFC 6890, DOI 10.17487/RFC6890, April 2013, . [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, . [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. Kasten, "Automatic Certificate Management Environment (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, . [RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019, . Ferro Expires 26 July 2026 [Page 34] 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, . [RFC919] Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC 919, DOI 10.17487/RFC0919, October 1984, . 14.2. Informative References [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, . [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, . [RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network Interconnect Devices", RFC 2544, DOI 10.17487/RFC2544, March 1999, . [RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix Reserved for Documentation", RFC 3849, DOI 10.17487/RFC3849, July 2004, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC5737] Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks Reserved for Documentation", RFC 5737, DOI 10.17487/RFC5737, January 2010, . [RFC6666] Hilliard, N. and D. Freedman, "A Discard Prefix for IPv6", RFC 6666, DOI 10.17487/RFC6666, August 2012, . Ferro Expires 26 July 2026 [Page 35] Internet-Draft ApertoDNS Protocol January 2026 [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, . 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 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 Ferro Expires 26 July 2026 [Page 36] Internet-Draft ApertoDNS Protocol January 2026 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: * 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 Ferro Expires 26 July 2026 [Page 37] Internet-Draft ApertoDNS Protocol January 2026 * 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 * 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 Ferro Expires 26 July 2026 [Page 38] Internet-Draft ApertoDNS Protocol January 2026 Appendix G. Changes from -01 This section summarizes changes from draft-ferro-dnsop-apertodns- protocol-01: G.1. Version 1.3.2 Changes (Response Consistency) * Standardized timestamp field naming across all endpoints: - Renamed timestamp to updated_at in /update response - Renamed last_updated to updated_at in /status response - This provides consistent naming for timestamp fields across the protocol * Changed /domains response structure from grouped domains to flat array: - Previous: data.domains[].hostnames[] (grouped by parent domain) - New: data[] (flat array of hostname objects with full details) - Each hostname object now includes: hostname, ipv4, ipv6, ttl, updated_at, created_at - This reduces API calls needed to retrieve hostname information * Clarified that timestamp field remains unchanged for /health and /txt endpoints * Clarified that server_time field remains unchanged for /info endpoint G.2. Version 1.3.2 Changes (Enhancements) * Added "Backward Compatibility" subsection to /update endpoint documenting deprecated field aliases (ipv4_previous, ipv6_previous) for transition from legacy field names * Added "Authorization Scopes" section documenting optional scope- based authorization with defined scopes: dns:update, domains:read, txt:read, txt:write, txt:delete * Updated example timestamps to 2026 Ferro Expires 26 July 2026 [Page 39] Internet-Draft ApertoDNS Protocol January 2026 G.3. Version 1.4.0 Changes (Record Deletion and Concurrency) * Added "Record Deletion via Null Values" subsection to /update endpoint documenting the ability to delete A or AAAA records by setting the corresponding field to null in the update request * Defined tri-state semantics for ipv4/ipv6 fields: string value (update), null (delete), omitted (no change) * Added examples for IPv4 and IPv6 record deletion * Added "Concurrency Model" section documenting last-write-wins semantics for concurrent updates to the same hostname * Added recommendations for conflict-sensitive applications * Expanded "IP Address Validation" section with explicit lists of rejected IPv4 (15 ranges) and IPv6 (9 ranges) address blocks per RFC 6890 * Added RFC 6890 to normative references * Updated protocol version to 1.4.0 Author's Address Andrea Ferro ApertoDNS Italy Email: support@apertodns.com Ferro Expires 26 July 2026 [Page 40]