A Telephone Number Mapping (ENUM) Service Registration for Instant Messaging (IM) Services
updated by
- rfc-6118 — Update of Legacy IANA Registrations of Enumservices
Extracted elements (10)
The 'im:' URI scheme was chosen as a protocol-agnostic identifier rather than registering enumservices for specific IM protocols (e.g., SIP or XMPP). This allows ENUM to return a single URI while RFC 3861's discovery mechanism handles protocol negotiation between querying party and target.
Unlike a traditional telephone number, an 'im:' URI resource may require cryptographic credentials for authentication and authorization before messages are exchanged. ENUM with IM protocols can therefore provide greater protection from unwanted callers than the PSTN, despite ENUM records being publicly available.
RFC 3861's address resolution mechanism is used to discover which specific IM protocol (e.g., SIP per RFC 3261, XMPP per RFC 3921) to use when resolving an 'im:' URI returned by ENUM, enabling interoperability across different IM systems.
Any instant messaging protocol used in conjunction with the 'im:' URI scheme is required to meet the security requirements detailed in RFC 2779 (authentication, integrity, confidentiality).
Depending on the structure of the 'im:' URI, publishing it in ENUM may reveal the full name or employer of the target. The use of anonymous URIs is recommended to mitigate this privacy risk.
The 'im' Enumservice indicates that the resource identified is an 'im:' URI. The 'im:' URI scheme does not identify any particular IM protocol; instead RFC 3861 is used to discover whether an IM protocol supported by the querying party is also supported by the target resource.
Registers the 'im' Enumservice with IANA per RFC 3761. The Enumservice Name and Type are both 'im', with no subtypes, and uses the 'im:' URI scheme.
DNS does not make policy decisions and all ENUM records must be assumed publicly available. Revealing an 'im:' URI may expose the full name or employer of the target; use of anonymous URIs mitigates this risk.
ENUM relies on DNS, which in its current form is insecure and provides no mechanism to ensure answers are authentic. DNSSEC mitigates this in zones where it is available, as referenced in RFC 3761 and RFC 3833.
IM protocols used with the 'im:' URI scheme are required to meet the security requirements of RFC 2779, including authentication, integrity, and confidentiality, to prevent message forgery and tampering.