]> ApertoDNS

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Operations and Management DNS Operations dynamic dns ddns dns update REST API 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.

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.

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 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.

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.

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 when, and only when, they appear in all capitals, as shown here.

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

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 .

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/.

Base URL Conforming implementations MUST serve all endpoints under: The use of well-known URIs ensures consistent endpoint discovery across providers.

Content Type All request and response bodies MUST use the application/json media type unless otherwise specified.

Response Format All responses MUST include a boolean success field at the top level: Or for errors:

Conformance Requirements This section defines the requirements for conforming implementations.

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.

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

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

Authentication

Supported Methods Protected endpoints require authentication via one of the following methods:

1. Bearer Token (RECOMMENDED) : 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.

Token Format Tokens SHOULD follow the format: 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

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.

Endpoints

Discovery Endpoint (/info) The discovery endpoint returns provider information, capabilities, and configuration. This endpoint MUST NOT require authentication.

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)

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

The capabilities object MAY include the following OPTIONAL fields:

Field	Type	Description
webhooks	boolean	Provider-specific webhook support available

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.

Example Response

Health Endpoint (/health) Returns service health status. This endpoint MUST NOT require authentication and SHOULD be used for monitoring.

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

Update Endpoint (/update) Updates DNS records for a single hostname. This endpoint MUST require authentication.

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)

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.

Example Request

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

Bulk Update Endpoint (/bulk-update) Updates multiple hostnames in a single request. Providers advertising bulk_update: true in capabilities MUST implement this endpoint.

Example Request

Example Response

Status Endpoint (/status/{hostname}) Returns current DNS record status for a hostname.

Example Response

Domains Endpoint (/domains) Returns list of domains and hostnames available to the authenticated user.

Example Response

Error Handling

HTTP Status Codes Implementations MUST use appropriate HTTP status codes as defined in :

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

Error Response Format

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

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

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

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

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

Comparison with RFC 2136 RFC 2136 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

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.

Security Considerations

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.

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

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.

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.

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.

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

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

• 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 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 before processing the request.

Privacy Considerations This section addresses privacy considerations as recommended by .

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

User Control Users SHOULD have mechanisms to:

• View their stored data
• Delete their accounts and associated data
• Export their data in a portable format

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.

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

IANA Considerations

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.

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. This specification describes how to use bearer tokens in HTTP requests to access OAuth 2.0 protected resources. Any party in possession of a bearer token (a "bearer") can use it to get access to the associated resources (without demonstrating possession of a cryptographic key). To prevent misuse, bearer tokens need to be protected from disclosure in storage and in transport. [STANDARDS-TRACK] This memo defines a path prefix for "well-known locations", "/.well-known/", in selected Uniform Resource Identifier (URI) schemes. In doing so, it obsoletes RFC 5785 and updates the URI schemes defined in RFC 7230 to reserve that space. It also updates RFC 7595 to track URI schemes that support well-known URIs in their registry. JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data. This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance. This document is the revised protocol definition for Internationalized Domain Names (IDNs). The rationale for changes, the relationship to the older specification, and important terminology are provided in other documents. This document specifies the protocol mechanism, called Internationalized Domain Names in Applications (IDNA), for registering and looking up IDNs in a way that does not require changes to the DNS itself. IDNA is only meant for processing domain names, not free text. [STANDARDS-TRACK] Informative References Using this specification of the UPDATE opcode, it is possible to add or delete RRs or RRsets from a specified zone. Prerequisites are specified separately from update operations, and can specify a dependency upon either the previous existence or nonexistence of an RRset, or the existence of a single RR. [STANDARDS-TRACK] This document offers guidance for developing privacy considerations for inclusion in protocol specifications. It aims to make designers, implementers, and users of Internet protocols aware of privacy-related design choices. It suggests that whether any individual RFC warrants a specific privacy considerations section will depend on the document's content.

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.

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.

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

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

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

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