This Recommendation | International Standard specifies the format and generation rules that enable users to produce 128-bit identifiers that are either guaranteed to be globally unique, or are globally unique with a high probability. The UUIDs generated in conformance with this Recommendation | International Standard are suitable either for transient use, with generation of a new UUID every 100 nanoseconds, or as persistent identifiers. This Recommendation | International Standard is derived from earlier non-standard specifications of UUIDs and their generation, and is technically identical to those earlier specifications. This Recommendation | International Standard specifies the procedures for the operation of a Web-based Registration Authority for UUIDs. This Recommendation | International Standard also specifies and allows the use of UUIDs (registered or not registered) as OID components under the arc {joint-iso-itu-t uuid(25)}. This enables users to generate OIDs without any registration procedures. This Recommendation | International Standard also specifies and allows the use of UUIDs (registered or not registered) to form a URN.