ASMUS, Inc. The IDNA specifications for internationalized domain names combine rules that determine the labels that are allowed in the DNS without violating the protocol itself and an assignment of responsibility, consistent with earlier specifications, for determining the labels that are allowed in particular zones. Conformance to IDNA by registries and other implementations requires both parts. Experience strongly suggests that the language describing those responsibility was insufficiently clear to promote safe and interoperable use of the specifications and that more details and some specific examples would have been helpful. This specification updates the earlier ones to provide that guidance and to correct some technical errors in the descriptions. It does not alter the protocols and rules themselves in any way.