The Internet Assigned Number Authority (IANA) tel Uniform Resource Identifier (URI) Parameter Registry
updates
- rfc-3966 — The tel URI for Telephone Numbers
Extracted elements (12)
Optional tel URI parameters should act as metadata about the identifier, providing additional information to a service rather than enabling the service itself. The service must operate normally even in the absence of optional parameters.
Rather than registering each predefined parameter value individually or creating a sub-registry per parameter, parameter values are registered by reference. The registry entry for a parameter contains references to the RFCs that define its accepted values, because parameters often take on a large number of values.
When a tel URI with a proposed parameter will be converted to a URI used by SIP or H.323, the Designated Expert must assess whether the parameter encapsulates signaling information (e.g., ISUP parameters) that is not meaningful to request processing in the converted URI's domain.
Documents defining tel URI parameters or parameter values MUST register them with IANA as described in Section 4. The registration policy is 'Specification Required, Designated Expert'.
New tel URI parameters and new values for existing tel URI parameters MUST be registered with IANA.
Tel URI parameters and values MUST be documented in an RFC or other permanent and readily available public specification before IANA registration. The documentation MUST fully explain the syntax, intended usage, and semantics of the parameter.
When registering a new tel URI parameter, the submitter MUST provide: the parameter name, whether it accepts only predefined values, and a reference to the RFC or public specification defining it.
When registering a new value for an existing tel URI parameter, the submitter MUST provide the parameter name and a reference to the RFC or public specification that defines the new value.
The initial registry contains 12 parameters: isub (Constrained, RFC3966), isub-encoding (Constrained, RFC4715), ext (Constrained, RFC3966), phone-context (Constrained, RFC3966), enumdi (No value, RFC4759), npdi (No value, RFC4694), rn (Constrained, RFC4694), rn-context (Constrained, RFC4694), cic (Constrained, RFC4694), cic-context (Constrained, RFC4694), tgrp (Constrained, RFC4904), trunk-context (Constrained, RFC4904).
The tel URI Parameters registry contains a 'Predefined Values' column with two possible values: 'Constrained' (the parameter accepts a defined set of values specified in its reference RFC) or 'No value' (the parameter is a flag or has no predefined value set).
This document creates the IANA registry named 'tel URI Parameters', which lists tel URI parameters and their values. The registry is populated with parameters from RFC 3966, RFC 4715, RFC 4694, RFC 4759, and RFC 4904.
The registry itself has no direct security considerations, but supporting RFC publications for all parameter registrations MUST provide detailed security considerations for the registered parameters.