DNS Operations A. Ferro Internet-Draft ApertoDNS Intended status: Standards Track 31 December 2025 Expires: 4 July 2026 ApertoDNS Protocol: A Modern Dynamic DNS Update Protocol draft-ferro-dnsop-apertodns-protocol-00 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, 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 4 July 2026. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components Ferro Expires 4 July 2026 [Page 1] Internet-Draft ApertoDNS Protocol December 2025 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. Note to Readers . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Protocol Versioning . . . . . . . . . . . . . . . . . . . 4 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 2.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Base URL . . . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Content Type . . . . . . . . . . . . . . . . . . . . . . 5 4.3. Response Format . . . . . . . . . . . . . . . . . . . . . 6 5. Conformance Requirements . . . . . . . . . . . . . . . . . . 6 5.1. Conformance Levels . . . . . . . . . . . . . . . . . . . 6 5.2. Capability Advertisement . . . . . . . . . . . . . . . . 6 5.3. Interoperability . . . . . . . . . . . . . . . . . . . . 6 6. Authentication . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. Supported Methods . . . . . . . . . . . . . . . . . . . . 7 6.2. Token Format . . . . . . . . . . . . . . . . . . . . . . 7 6.3. Token Transmission . . . . . . . . . . . . . . . . . . . 7 7. Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Discovery Endpoint (/info) . . . . . . . . . . . . . . . 8 7.1.1. Response Fields . . . . . . . . . . . . . . . . . . . 8 7.1.2. Capability Fields . . . . . . . . . . . . . . . . . . 8 7.1.3. Example Response . . . . . . . . . . . . . . . . . . 9 7.2. Health Endpoint (/health) . . . . . . . . . . . . . . . . 10 7.2.1. Example Response . . . . . . . . . . . . . . . . . . 10 7.3. Update Endpoint (/update) . . . . . . . . . . . . . . . . 11 7.3.1. Request Fields . . . . . . . . . . . . . . . . . . . 11 7.3.2. Example Request . . . . . . . . . . . . . . . . . . . 11 7.3.3. Example Response . . . . . . . . . . . . . . . . . . 12 7.4. Bulk Update Endpoint (/bulk-update) . . . . . . . . . . . 12 7.4.1. Example Request . . . . . . . . . . . . . . . . . . . 12 7.4.2. Example Response . . . . . . . . . . . . . . . . . . 12 7.5. Status Endpoint (/status/{hostname}) . . . . . . . . . . 13 7.5.1. Example Response . . . . . . . . . . . . . . . . . . 13 7.6. Domains Endpoint (/domains) . . . . . . . . . . . . . . . 13 7.6.1. Example Response . . . . . . . . . . . . . . . . . . 14 8. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 14 8.1. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 14 8.2. Error Response Format . . . . . . . . . . . . . . . . . . 15 8.3. Standard Error Codes . . . . . . . . . . . . . . . . . . 15 8.4. Rate Limiting Headers . . . . . . . . . . . . . . . . . . 15 9. Legacy Compatibility . . . . . . . . . . . . . . . . . . . . 16 Ferro Expires 4 July 2026 [Page 2] Internet-Draft ApertoDNS Protocol December 2025 9.1. Legacy Response Codes . . . . . . . . . . . . . . . . . . 16 10. Comparison with RFC 2136 . . . . . . . . . . . . . . . . . . 16 11. Security Considerations . . . . . . . . . . . . . . . . . . . 17 11.1. Transport Security . . . . . . . . . . . . . . . . . . . 17 11.2. Token Security . . . . . . . . . . . . . . . . . . . . . 17 11.3. Hostname Validation . . . . . . . . . . . . . . . . . . 18 11.4. Rate Limiting . . . . . . . . . . . . . . . . . . . . . 18 11.5. DNS Rebinding Prevention . . . . . . . . . . . . . . . . 18 11.6. Input Validation . . . . . . . . . . . . . . . . . . . . 18 11.7. Internationalized Domain Names . . . . . . . . . . . . . 18 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19 12.1. Data Minimization . . . . . . . . . . . . . . . . . . . 19 12.2. User Control . . . . . . . . . . . . . . . . . . . . . . 19 12.3. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 19 12.4. Encryption . . . . . . . . . . . . . . . . . . . . . . . 20 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 13.1. Well-Known URI Registration . . . . . . . . . . . . . . 20 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 14.1. Normative References . . . . . . . . . . . . . . . . . . 20 14.2. Informative References . . . . . . . . . . . . . . . . . 21 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 21 Appendix B. Implementation Status . . . . . . . . . . . . . . . 21 B.1. ApertoDNS . . . . . . . . . . . . . . . . . . . . . . . . 21 Appendix C. OpenAPI Specification . . . . . . . . . . . . . . . 22 Appendix D. Example Update Flow . . . . . . . . . . . . . . . . 22 Appendix E. Changes from Legacy DDNS Protocols . . . . . . . . . 23 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23 1. Note to Readers Discussion of this document takes place on the DNS Operations Working Group mailing list (dnsop@ietf.org). Source for this draft and an issue tracker can be found at https://github.com/apertodns/apertodns-protocol. 2. 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. Ferro Expires 4 July 2026 [Page 3] Internet-Draft ApertoDNS Protocol December 2025 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. 2.1. Protocol Versioning The protocol version specified in discovery responses (e.g., "1.2.0") 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., "-00") tracks the IETF document revision process separately. 2.2. 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. 2.3. 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 Ferro Expires 4 July 2026 [Page 4] Internet-Draft ApertoDNS Protocol December 2025 * *Backward compatible*: Optional legacy endpoint for existing clients 3. 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]. 4. 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/. 4.1. 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. 4.2. Content Type All request and response bodies MUST use the application/json media type [RFC8259] unless otherwise specified. Ferro Expires 4 July 2026 [Page 5] Internet-Draft ApertoDNS Protocol December 2025 4.3. 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" } } 5. Conformance Requirements This section defines the requirements for conforming implementations. 5.1. 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. 5.2. Capability Advertisement Implementations MUST accurately advertise their capabilities in the /info endpoint response. Implementations MUST NOT advertise capabilities they do not support. 5.3. Interoperability Implementations SHOULD accept requests from any conforming client. Implementations MUST NOT require proprietary extensions for basic DDNS functionality. Ferro Expires 4 July 2026 [Page 6] Internet-Draft ApertoDNS Protocol December 2025 6. Authentication 6.1. 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. 6.2. 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 6.3. 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. Ferro Expires 4 July 2026 [Page 7] Internet-Draft ApertoDNS Protocol December 2025 7. Endpoints 7.1. Discovery Endpoint (/info) GET /.well-known/apertodns/v1/info The discovery endpoint returns provider information, capabilities, and configuration. This endpoint MUST NOT require authentication. 7.1.1. Response Fields +==================+========+==========+=====================+ | Field | Type | Required | Description | +==================+========+==========+=====================+ | protocol | string | YES | MUST be "apertodns" | +------------------+--------+----------+---------------------+ | protocol_version | string | YES | Semantic version | | | | | (e.g., "1.2.0") | +------------------+--------+----------+---------------------+ | 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 | | | | | (ISO 8601) | +------------------+--------+----------+---------------------+ Table 1 7.1.2. Capability Fields The capabilities object MUST include the following fields: Ferro Expires 4 July 2026 [Page 8] Internet-Draft ApertoDNS Protocol December 2025 +===================+=========+====================================+ | 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 | +----------+---------+---------------------------------------------+ 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. The capabilities object MAY include additional fields for future extensions. Unknown capability fields SHOULD be ignored by clients. 7.1.3. Example Response Ferro Expires 4 July 2026 [Page 9] Internet-Draft ApertoDNS Protocol December 2025 { "success": true, "data": { "protocol": "apertodns", "protocol_version": "1.2.0", "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" } } 7.2. 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. 7.2.1. Example Response Ferro Expires 4 July 2026 [Page 10] Internet-Draft ApertoDNS Protocol December 2025 { "success": true, "data": { "status": "healthy", "timestamp": "2025-01-01T12:00:00.000Z" } } The status field MUST be one of: "healthy", "degraded", or "unhealthy". 7.3. 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. 7.3.1. 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. The special value "auto" instructs the server to detect the client's IP address from the incoming request. 7.3.2. Example Request Ferro Expires 4 July 2026 [Page 11] Internet-Draft ApertoDNS Protocol December 2025 { "hostname": "home.example.com", "ipv4": "auto", "ttl": 300 } 7.3.3. Example Response { "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). 7.4. 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. 7.4.1. Example Request { "updates": [ {"hostname": "home.example.com", "ipv4": "auto"}, {"hostname": "office.example.com", "ipv4": "203.0.113.51"} ] } 7.4.2. Example Response Ferro Expires 4 July 2026 [Page 12] Internet-Draft ApertoDNS Protocol December 2025 { "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 } ] } } 7.5. Status Endpoint (/status/{hostname}) GET /.well-known/apertodns/v1/status/{hostname} Authorization: Bearer {token} Returns current DNS record status for a hostname. 7.5.1. 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" } } 7.6. Domains Endpoint (/domains) Ferro Expires 4 July 2026 [Page 13] Internet-Draft ApertoDNS Protocol December 2025 GET /.well-known/apertodns/v1/domains Authorization: Bearer {token} Returns list of domains and hostnames available to the authenticated user. 7.6.1. Example Response { "success": true, "data": { "domains": [ { "domain": "example.com", "hostnames": ["home.example.com", "office.example.com"] } ] } } 8. Error Handling 8.1. 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 5 Ferro Expires 4 July 2026 [Page 14] Internet-Draft ApertoDNS Protocol December 2025 8.2. Error Response Format { "success": false, "error": { "code": "error_code", "message": "Human-readable description" } } 8.3. 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 | +--------------------+-------------+-----------------------------+ Table 6 8.4. 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 Ferro Expires 4 July 2026 [Page 15] Internet-Draft ApertoDNS Protocol December 2025 9. Legacy Compatibility For backward compatibility with existing DDNS clients, providers MAY implement: GET /nic/update?hostname={hostname}&myip={ip} Authorization: Basic {credentials} 9.1. 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 7 This endpoint is provided for compatibility only. New implementations SHOULD use the modern JSON endpoints. 10. 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: Ferro Expires 4 July 2026 [Page 16] Internet-Draft ApertoDNS Protocol December 2025 +===========+=================+====================+ | 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 8 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. 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 Ferro Expires 4 July 2026 [Page 17] Internet-Draft ApertoDNS Protocol December 2025 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. 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. 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. 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 11.7. 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 Ferro Expires 4 July 2026 [Page 18] Internet-Draft ApertoDNS Protocol December 2025 * Servers MUST store and return hostnames in a consistent form For example, a client wishing to update an IDN hostname (U-label form) SHOULD send the request with the A-label form (e.g., "xn-- r8jz45g.example.com"). Implementations that accept U-label input MUST perform IDNA2008 validation as specified in [RFC5891] before processing the request. 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. Ferro Expires 4 July 2026 [Page 19] Internet-Draft ApertoDNS Protocol December 2025 12.4. Encryption All communications MUST be encrypted via HTTPS, preventing passive observation of update requests and tokens. 13. IANA Considerations 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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5891] Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, August 2010, . [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Ferro Expires 4 July 2026 [Page 20] Internet-Draft ApertoDNS Protocol December 2025 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, . [RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019, . [RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, . 14.2. 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, . [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. 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 Ferro Expires 4 July 2026 [Page 21] Internet-Draft ApertoDNS Protocol December 2025 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 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 Ferro Expires 4 July 2026 [Page 22] Internet-Draft ApertoDNS Protocol December 2025 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 * Bulk update support for multiple hostnames * Well-known URI path for consistent discovery Author's Address Andrea Ferro ApertoDNS Italy Email: support@apertodns.com Ferro Expires 4 July 2026 [Page 23]