A Universally Unique IDentifier (UUID) URN Namespace
RFC 4122

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Network Working Group                                           P. Leach
Request for Comments: 4122                                     Microsoft
Category: Standards Track                                    M. Mealling
                                                Refactored Networks, LLC
                                                                 R. Salz
                                              DataPower Technology, Inc.
                                                               July 2005

          A Universally Unique IDentifier (UUID) URN Namespace

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This specification defines a Uniform Resource Name namespace for
   UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
   Unique IDentifier).  A UUID is 128 bits long, and can guarantee
   uniqueness across space and time.  UUIDs were originally used in the
   Apollo Network Computing System and later in the Open Software
   Foundation's (OSF) Distributed Computing Environment (DCE), and then
   in Microsoft Windows platforms.

   This specification is derived from the DCE specification with the
   kind permission of the OSF (now known as The Open Group).
   Information from earlier versions of the DCE specification have been
   incorporated into this document.

Leach, et al.               Standards Track                     [Page 1]
RFC 4122                  A UUID URN Namespace                 July 2005

Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3. Namespace Registration Template  . . . . . . . . . . . . . . .  3
   4. Specification  . . . . . . . . . . . . . . . . . . . . . . . .  5
      4.1. Format. . . . . . . . . . . . . . . . . . . . . . . . . .  5
           4.1.1. Variant. . . . . . . . . . . . . . . . . . . . . .  6
           4.1.2. Layout and Byte Order. . . . . . . . . . . . . . .  6
           4.1.3. Version. . . . . . . . . . . . . . . . . . . . . .  7
           4.1.4. Timestamp. . . . . . . . . . . . . . . . . . . . .  8
           4.1.5. Clock Sequence . . . . . . . . . . . . . . . . . .  8
           4.1.6. Node . . . . . . . . . . . . . . . . . . . . . . .  9
           4.1.7. Nil UUID . . . . . . . . . . . . . . . . . . . . .  9
      4.2. Algorithms for Creating a Time-Based UUID . . . . . . . .  9
           4.2.1. Basic Algorithm. . . . . . . . . . . . . . . . . . 10
           4.2.2. Generation Details . . . . . . . . . . . . . . . . 12
      4.3. Algorithm for Creating a Name-Based UUID. . . . . . . . . 13
      4.4. Algorithms for Creating a UUID from Truly Random or
           Pseudo-Random Numbers . . . . . . . . . . . . . . . . . . 14
      4.5. Node IDs that Do Not Identify the Host. . . . . . . . . . 15
   5. Community Considerations . . . . . . . . . . . . . . . . . . . 15
   6. Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   8. Normative References . . . . . . . . . . . . . . . . . . . . . 16
   A. Appendix A - Sample Implementation . . . . . . . . . . . . . . 18
   B. Appendix B - Sample Output of utest  . . . . . . . . . . . . . 29
   C. Appendix C - Some Name Space IDs . . . . . . . . . . . . . . . 30

1.  Introduction

   This specification defines a Uniform Resource Name namespace for
   UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
   Unique IDentifier).  A UUID is 128 bits long, and requires no central
   registration process.

   The information here is meant to be a concise guide for those wishing
   to implement services using UUIDs as URNs.  Nothing in this document
   should be construed to override the DCE standards that defined UUIDs.

   There is an ITU-T Recommendation and ISO/IEC Standard [3] that are
   derived from earlier versions of this document.  Both sets of
   specifications have been aligned, and are fully technically
   compatible.  In addition, a global registration function is being
   provided by the Telecommunications Standardisation Bureau of ITU-T;
   for details see <http://www.itu.int/ITU-T/asn1/uuid.html>.

Leach, et al.               Standards Track                     [Page 2]
RFC 4122                  A UUID URN Namespace                 July 2005

2.  Motivation

   One of the main reasons for using UUIDs is that no centralized
   authority is required to administer them (although one format uses
   IEEE 802 node identifiers, others do not).  As a result, generation