ITU-T X.667 PDF

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 primary values (which define Unicode labels) for arcs beneath the Joint UUID arc. This enables users to generate and use such arcs without any registration procedures.

This Recommendation | International Standard also specifies and allows the use of UUIDs (registered or not registered) to form a URN.