6. Well-Known Registration Status Terminology

6. Well-Known Registration Status Terminology

The following labels describe the status of an assignment or range of assignments:

Private Use: Private use only (not assigned), as described in Section 4.1.

Experimental: Available for general experimental use as described in [RFC3692]. IANA does not record specific assignments for any particular use.

Unassigned: Not currently assigned, and available for assignment via documented procedures. While it's generally clear that any values that are not registered are unassigned and available for assignment, it is sometimes useful to explicitly specify that situation. Note that this is distinctly different from "Reserved".

Reserved: Not assigned and not available for assignment. Reserved values are held for special uses, such as to extend the namespace when it becomes exhausted. "Reserved" is also sometimes used to designate values that had been assigned but are no longer in use, keeping them set aside as long as other unassigned values are available. Note that this is distinctly different from "Unassigned".

Reserved values can be released for assignment by the change controller for the registry (this is often the IESG, for registries created by RFCs in the IETF stream).

Known Unregistered Use: It's known that the assignment or range is in use without having been defined in accordance with reasonable practice. Documentation for use of the assignment or range may be unavailable, inadequate, or conflicting. This is a warning against use, as well as an alert to network operators who might see these values in use on their networks.