7 Network Working Group P. Leach
8 Request for Comments: 4122 Microsoft
9 Category: Standards Track M. Mealling
10 Refactored Networks, LLC
12 DataPower Technology, Inc.
16 A Universally Unique IDentifier (UUID) URN Namespace
20 This document specifies an Internet standards track protocol for the
21 Internet community, and requests discussion and suggestions for
22 improvements. Please refer to the current edition of the "Internet
23 Official Protocol Standards" (STD 1) for the standardization state
24 and status of this protocol. Distribution of this memo is unlimited.
28 Copyright (C) The Internet Society (2005).
32 This specification defines a Uniform Resource Name namespace for
33 UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
34 Unique IDentifier). A UUID is 128 bits long, and can guarantee
35 uniqueness across space and time. UUIDs were originally used in the
36 Apollo Network Computing System and later in the Open Software
37 Foundation's (OSF) Distributed Computing Environment (DCE), and then
38 in Microsoft Windows platforms.
40 This specification is derived from the DCE specification with the
41 kind permission of the OSF (now known as The Open Group).
42 Information from earlier versions of the DCE specification have been
43 incorporated into this document.
58 Leach, et al. Standards Track [Page 1]
60 RFC 4122 A UUID URN Namespace July 2005
65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
66 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
67 3. Namespace Registration Template . . . . . . . . . . . . . . . 3
68 4. Specification . . . . . . . . . . . . . . . . . . . . . . . . 5
69 4.1. Format. . . . . . . . . . . . . . . . . . . . . . . . . . 5
70 4.1.1. Variant. . . . . . . . . . . . . . . . . . . . . . 6
71 4.1.2. Layout and Byte Order. . . . . . . . . . . . . . . 6
72 4.1.3. Version. . . . . . . . . . . . . . . . . . . . . . 7
73 4.1.4. Timestamp. . . . . . . . . . . . . . . . . . . . . 8
74 4.1.5. Clock Sequence . . . . . . . . . . . . . . . . . . 8
75 4.1.6. Node . . . . . . . . . . . . . . . . . . . . . . . 9
76 4.1.7. Nil UUID . . . . . . . . . . . . . . . . . . . . . 9
77 4.2. Algorithms for Creating a Time-Based UUID . . . . . . . . 9
78 4.2.1. Basic Algorithm. . . . . . . . . . . . . . . . . . 10
79 4.2.2. Generation Details . . . . . . . . . . . . . . . . 12
80 4.3. Algorithm for Creating a Name-Based UUID. . . . . . . . . 13
81 4.4. Algorithms for Creating a UUID from Truly Random or
82 Pseudo-Random Numbers . . . . . . . . . . . . . . . . . . 14
83 4.5. Node IDs that Do Not Identify the Host. . . . . . . . . . 15
84 5. Community Considerations . . . . . . . . . . . . . . . . . . . 15
85 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
86 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
87 8. Normative References . . . . . . . . . . . . . . . . . . . . . 16
88 A. Appendix A - Sample Implementation . . . . . . . . . . . . . . 18
89 B. Appendix B - Sample Output of utest . . . . . . . . . . . . . 29
90 C. Appendix C - Some Name Space IDs . . . . . . . . . . . . . . . 30
94 This specification defines a Uniform Resource Name namespace for
95 UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
96 Unique IDentifier). A UUID is 128 bits long, and requires no central
99 The information here is meant to be a concise guide for those wishing
100 to implement services using UUIDs as URNs. Nothing in this document
101 should be construed to override the DCE standards that defined UUIDs.
103 There is an ITU-T Recommendation and ISO/IEC Standard [3] that are
104 derived from earlier versions of this document. Both sets of
105 specifications have been aligned, and are fully technically
106 compatible. In addition, a global registration function is being
107 provided by the Telecommunications Standardisation Bureau of ITU-T;
108 for details see <http://www.itu.int/ITU-T/asn1/uuid.html>.
114 Leach, et al. Standards Track [Page 2]
116 RFC 4122 A UUID URN Namespace July 2005
121 One of the main reasons for using UUIDs is that no centralized
122 authority is required to administer them (although one format uses
123 IEEE 802 node identifiers, others do not). As a result, generation
124 on demand can be completely automated, and used for a variety of
125 purposes. The UUID generation algorithm described here supports very
126 high allocation rates of up to 10 million per second per machine if
127 necessary, so that they could even be used as transaction IDs.
129 UUIDs are of a fixed size (128 bits) which is reasonably small
130 compared to other alternatives. This lends itself well to sorting,
131 ordering, and hashing of all sorts, storing in databases, simple
132 allocation, and ease of programming in general.
134 Since UUIDs are unique and persistent, they make excellent Uniform
135 Resource Names. The unique ability to generate a new UUID without a
136 registration process allows for UUIDs to be one of the URNs with the
139 3. Namespace Registration Template
142 Registration Information:
143 Registration date: 2003-10-01
145 Declared registrant of the namespace:
146 JTC 1/SC6 (ASN.1 Rapporteur Group)
148 Declaration of syntactic structure:
149 A UUID is an identifier that is unique across both space and time,
150 with respect to the space of all UUIDs. Since a UUID is a fixed
151 size and contains a time field, it is possible for values to
152 rollover (around A.D. 3400, depending on the specific algorithm
153 used). A UUID can be used for multiple purposes, from tagging
154 objects with an extremely short lifetime, to reliably identifying
155 very persistent objects across a network.
157 The internal representation of a UUID is a specific sequence of
158 bits in memory, as described in Section 4. To accurately
159 represent a UUID as a URN, it is necessary to convert the bit
160 sequence to a string representation.
162 Each field is treated as an integer and has its value printed as a
163 zero-filled hexadecimal digit string with the most significant
164 digit first. The hexadecimal values "a" through "f" are output as
165 lower case characters and are case insensitive on input.
170 Leach, et al. Standards Track [Page 3]
172 RFC 4122 A UUID URN Namespace July 2005
175 The formal definition of the UUID string representation is
176 provided by the following ABNF [7]:
178 UUID = time-low "-" time-mid "-"
179 time-high-and-version "-"
180 clock-seq-and-reserved
181 clock-seq-low "-" node
184 time-high-and-version = 2hexOctet
185 clock-seq-and-reserved = hexOctet
186 clock-seq-low = hexOctet
188 hexOctet = hexDigit hexDigit
190 "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" /
191 "a" / "b" / "c" / "d" / "e" / "f" /
192 "A" / "B" / "C" / "D" / "E" / "F"
194 The following is an example of the string representation of a UUID as
197 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
199 Relevant ancillary documentation:
201 Identifier uniqueness considerations:
202 This document specifies three algorithms to generate UUIDs: the
203 first leverages the unique values of 802 MAC addresses to
204 guarantee uniqueness, the second uses pseudo-random number
205 generators, and the third uses cryptographic hashing and
206 application-provided text strings. As a result, the UUIDs
207 generated according to the mechanisms here will be unique from all
208 other UUIDs that have been or will be assigned.
210 Identifier persistence considerations:
211 UUIDs are inherently very difficult to resolve in a global sense.
212 This, coupled with the fact that UUIDs are temporally unique
213 within their spatial context, ensures that UUIDs will remain as
214 persistent as possible.
216 Process of identifier assignment:
217 Generating a UUID does not require that a registration authority
218 be contacted. One algorithm requires a unique value over space
219 for each generator. This value is typically an IEEE 802 MAC
220 address, usually already available on network-connected hosts.
221 The address can be assigned from an address block obtained from
222 the IEEE registration authority. If no such address is available,
226 Leach, et al. Standards Track [Page 4]
228 RFC 4122 A UUID URN Namespace July 2005
231 or privacy concerns make its use undesirable, Section 4.5
232 specifies two alternatives. Another approach is to use version 3
233 or version 4 UUIDs as defined below.
235 Process for identifier resolution:
236 Since UUIDs are not globally resolvable, this is not applicable.
238 Rules for Lexical Equivalence:
239 Consider each field of the UUID to be an unsigned integer as shown
240 in the table in section Section 4.1.2. Then, to compare a pair of
241 UUIDs, arithmetically compare the corresponding fields from each
242 UUID in order of significance and according to their data type.
243 Two UUIDs are equal if and only if all the corresponding fields
246 As an implementation note, equality comparison can be performed on
247 many systems by doing the appropriate byte-order canonicalization,
248 and then treating the two UUIDs as 128-bit unsigned integers.
250 UUIDs, as defined in this document, can also be ordered
251 lexicographically. For a pair of UUIDs, the first one follows the
252 second if the most significant field in which the UUIDs differ is
253 greater for the first UUID. The second precedes the first if the
254 most significant field in which the UUIDs differ is greater for
257 Conformance with URN Syntax:
258 The string representation of a UUID is fully compatible with the
259 URN syntax. When converting from a bit-oriented, in-memory
260 representation of a UUID into a URN, care must be taken to
261 strictly adhere to the byte order issues mentioned in the string
262 representation section.
264 Validation mechanism:
265 Apart from determining whether the timestamp portion of the UUID
266 is in the future and therefore not yet assignable, there is no
267 mechanism for determining whether a UUID is 'valid'.
270 UUIDs are global in scope.
276 The UUID format is 16 octets; some bits of the eight octet variant
277 field specified below determine finer structure.
282 Leach, et al. Standards Track [Page 5]
284 RFC 4122 A UUID URN Namespace July 2005
289 The variant field determines the layout of the UUID. That is, the
290 interpretation of all other bits in the UUID depends on the setting
291 of the bits in the variant field. As such, it could more accurately
292 be called a type field; we retain the original term for
293 compatibility. The variant field consists of a variable number of
294 the most significant bits of octet 8 of the UUID.
296 The following table lists the contents of the variant field, where
297 the letter "x" indicates a "don't-care" value.
299 Msb0 Msb1 Msb2 Description
301 0 x x Reserved, NCS backward compatibility.
303 1 0 x The variant specified in this document.
305 1 1 0 Reserved, Microsoft Corporation backward
308 1 1 1 Reserved for future definition.
310 Interoperability, in any form, with variants other than the one
311 defined here is not guaranteed, and is not likely to be an issue in
314 4.1.2. Layout and Byte Order
316 To minimize confusion about bit assignments within octets, the UUID
317 record definition is defined only in terms of fields that are
318 integral numbers of octets. The fields are presented with the most
319 significant one first.
321 Field Data Type Octet Note
324 time_low unsigned 32 0-3 The low field of the
325 bit integer timestamp
327 time_mid unsigned 16 4-5 The middle field of the
328 bit integer timestamp
330 time_hi_and_version unsigned 16 6-7 The high field of the
331 bit integer timestamp multiplexed
332 with the version number
338 Leach, et al. Standards Track [Page 6]
340 RFC 4122 A UUID URN Namespace July 2005
343 clock_seq_hi_and_rese unsigned 8 8 The high field of the
344 rved bit integer clock sequence
348 clock_seq_low unsigned 8 9 The low field of the
349 bit integer clock sequence
351 node unsigned 48 10-15 The spatially unique
352 bit integer node identifier
354 In the absence of explicit application or presentation protocol
355 specification to the contrary, a UUID is encoded as a 128-bit object,
358 The fields are encoded as 16 octets, with the sizes and order of the
359 fields defined above, and with each field encoded with the Most
360 Significant Byte first (known as network byte order). Note that the
361 field names, particularly for multiplexed fields, follow historical
365 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
369 | time_mid | time_hi_and_version |
370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
371 |clk_seq_hi_res | clk_seq_low | node (0-1) |
372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
374 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
378 The version number is in the most significant 4 bits of the time
379 stamp (bits 4 through 7 of the time_hi_and_version field).
381 The following table lists the currently-defined versions for this
384 Msb0 Msb1 Msb2 Msb3 Version Description
386 0 0 0 1 1 The time-based version
387 specified in this document.
389 0 0 1 0 2 DCE Security version, with
394 Leach, et al. Standards Track [Page 7]
396 RFC 4122 A UUID URN Namespace July 2005
399 0 0 1 1 3 The name-based version
400 specified in this document
401 that uses MD5 hashing.
403 0 1 0 0 4 The randomly or pseudo-
404 randomly generated version
405 specified in this document.
407 0 1 0 1 5 The name-based version
408 specified in this document
409 that uses SHA-1 hashing.
411 The version is more accurately a sub-type; again, we retain the term
416 The timestamp is a 60-bit value. For UUID version 1, this is
417 represented by Coordinated Universal Time (UTC) as a count of 100-
418 nanosecond intervals since 00:00:00.00, 15 October 1582 (the date of
419 Gregorian reform to the Christian calendar).
421 For systems that do not have UTC available, but do have the local
422 time, they may use that instead of UTC, as long as they do so
423 consistently throughout the system. However, this is not recommended
424 since generating the UTC from local time only needs a time zone
427 For UUID version 3 or 5, the timestamp is a 60-bit value constructed
428 from a name as described in Section 4.3.
430 For UUID version 4, the timestamp is a randomly or pseudo-randomly
431 generated 60-bit value, as described in Section 4.4.
433 4.1.5. Clock Sequence
435 For UUID version 1, the clock sequence is used to help avoid
436 duplicates that could arise when the clock is set backwards in time
437 or if the node ID changes.
439 If the clock is set backwards, or might have been set backwards
440 (e.g., while the system was powered off), and the UUID generator can
441 not be sure that no UUIDs were generated with timestamps larger than
442 the value to which the clock was set, then the clock sequence has to
443 be changed. If the previous value of the clock sequence is known, it
444 can just be incremented; otherwise it should be set to a random or
445 high-quality pseudo-random value.
450 Leach, et al. Standards Track [Page 8]
452 RFC 4122 A UUID URN Namespace July 2005
455 Similarly, if the node ID changes (e.g., because a network card has
456 been moved between machines), setting the clock sequence to a random
457 number minimizes the probability of a duplicate due to slight
458 differences in the clock settings of the machines. If the value of
459 clock sequence associated with the changed node ID were known, then
460 the clock sequence could just be incremented, but that is unlikely.
462 The clock sequence MUST be originally (i.e., once in the lifetime of
463 a system) initialized to a random number to minimize the correlation
464 across systems. This provides maximum protection against node
465 identifiers that may move or switch from system to system rapidly.
466 The initial value MUST NOT be correlated to the node identifier.
468 For UUID version 3 or 5, the clock sequence is a 14-bit value
469 constructed from a name as described in Section 4.3.
471 For UUID version 4, clock sequence is a randomly or pseudo-randomly
472 generated 14-bit value as described in Section 4.4.
476 For UUID version 1, the node field consists of an IEEE 802 MAC
477 address, usually the host address. For systems with multiple IEEE
478 802 addresses, any available one can be used. The lowest addressed
479 octet (octet number 10) contains the global/local bit and the
480 unicast/multicast bit, and is the first octet of the address
481 transmitted on an 802.3 LAN.
483 For systems with no IEEE address, a randomly or pseudo-randomly
484 generated value may be used; see Section 4.5. The multicast bit must
485 be set in such addresses, in order that they will never conflict with
486 addresses obtained from network cards.
488 For UUID version 3 or 5, the node field is a 48-bit value constructed
489 from a name as described in Section 4.3.
491 For UUID version 4, the node field is a randomly or pseudo-randomly
492 generated 48-bit value as described in Section 4.4.
496 The nil UUID is special form of UUID that is specified to have all
497 128 bits set to zero.
499 4.2. Algorithms for Creating a Time-Based UUID
501 Various aspects of the algorithm for creating a version 1 UUID are
502 discussed in the following sections.
506 Leach, et al. Standards Track [Page 9]
508 RFC 4122 A UUID URN Namespace July 2005
511 4.2.1. Basic Algorithm
513 The following algorithm is simple, correct, and inefficient:
515 o Obtain a system-wide global lock
517 o From a system-wide shared stable store (e.g., a file), read the
518 UUID generator state: the values of the timestamp, clock sequence,
519 and node ID used to generate the last UUID.
521 o Get the current time as a 60-bit count of 100-nanosecond intervals
522 since 00:00:00.00, 15 October 1582.
524 o Get the current node ID.
526 o If the state was unavailable (e.g., non-existent or corrupted), or
527 the saved node ID is different than the current node ID, generate
528 a random clock sequence value.
530 o If the state was available, but the saved timestamp is later than
531 the current timestamp, increment the clock sequence value.
533 o Save the state (current timestamp, clock sequence, and node ID)
534 back to the stable store.
536 o Release the global lock.
538 o Format a UUID from the current timestamp, clock sequence, and node
539 ID values according to the steps in Section 4.2.2.
541 If UUIDs do not need to be frequently generated, the above algorithm
542 may be perfectly adequate. For higher performance requirements,
543 however, issues with the basic algorithm include:
545 o Reading the state from stable storage each time is inefficient.
547 o The resolution of the system clock may not be 100-nanoseconds.
549 o Writing the state to stable storage each time is inefficient.
551 o Sharing the state across process boundaries may be inefficient.
553 Each of these issues can be addressed in a modular fashion by local
554 improvements in the functions that read and write the state and read
555 the clock. We address each of them in turn in the following
562 Leach, et al. Standards Track [Page 10]
564 RFC 4122 A UUID URN Namespace July 2005
567 4.2.1.1. Reading Stable Storage
569 The state only needs to be read from stable storage once at boot
570 time, if it is read into a system-wide shared volatile store (and
571 updated whenever the stable store is updated).
573 If an implementation does not have any stable store available, then
574 it can always say that the values were unavailable. This is the
575 least desirable implementation because it will increase the frequency
576 of creation of new clock sequence numbers, which increases the
577 probability of duplicates.
579 If the node ID can never change (e.g., the net card is inseparable
580 from the system), or if any change also reinitializes the clock
581 sequence to a random value, then instead of keeping it in stable
582 store, the current node ID may be returned.
584 4.2.1.2. System Clock Resolution
586 The timestamp is generated from the system time, whose resolution may
587 be less than the resolution of the UUID timestamp.
589 If UUIDs do not need to be frequently generated, the timestamp can
590 simply be the system time multiplied by the number of 100-nanosecond
591 intervals per system time interval.
593 If a system overruns the generator by requesting too many UUIDs
594 within a single system time interval, the UUID service MUST either
595 return an error, or stall the UUID generator until the system clock
598 A high resolution timestamp can be simulated by keeping a count of
599 the number of UUIDs that have been generated with the same value of
600 the system time, and using it to construct the low order bits of the
601 timestamp. The count will range between zero and the number of
602 100-nanosecond intervals per system time interval.
604 Note: If the processors overrun the UUID generation frequently,
605 additional node identifiers can be allocated to the system, which
606 will permit higher speed allocation by making multiple UUIDs
607 potentially available for each time stamp value.
609 4.2.1.3. Writing Stable Storage
611 The state does not always need to be written to stable store every
612 time a UUID is generated. The timestamp in the stable store can be
613 periodically set to a value larger than any yet used in a UUID. As
614 long as the generated UUIDs have timestamps less than that value, and
618 Leach, et al. Standards Track [Page 11]
620 RFC 4122 A UUID URN Namespace July 2005
623 the clock sequence and node ID remain unchanged, only the shared
624 volatile copy of the state needs to be updated. Furthermore, if the
625 timestamp value in stable store is in the future by less than the
626 typical time it takes the system to reboot, a crash will not cause a
627 reinitialization of the clock sequence.
629 4.2.1.4. Sharing State Across Processes
631 If it is too expensive to access shared state each time a UUID is
632 generated, then the system-wide generator can be implemented to
633 allocate a block of time stamps each time it is called; a per-
634 process generator can allocate from that block until it is exhausted.
636 4.2.2. Generation Details
638 Version 1 UUIDs are generated according to the following algorithm:
640 o Determine the values for the UTC-based timestamp and clock
641 sequence to be used in the UUID, as described in Section 4.2.1.
643 o For the purposes of this algorithm, consider the timestamp to be a
644 60-bit unsigned integer and the clock sequence to be a 14-bit
645 unsigned integer. Sequentially number the bits in a field,
646 starting with zero for the least significant bit.
648 o Set the time_low field equal to the least significant 32 bits
649 (bits zero through 31) of the timestamp in the same order of
652 o Set the time_mid field equal to bits 32 through 47 from the
653 timestamp in the same order of significance.
655 o Set the 12 least significant bits (bits zero through 11) of the
656 time_hi_and_version field equal to bits 48 through 59 from the
657 timestamp in the same order of significance.
659 o Set the four most significant bits (bits 12 through 15) of the
660 time_hi_and_version field to the 4-bit version number
661 corresponding to the UUID version being created, as shown in the
664 o Set the clock_seq_low field to the eight least significant bits
665 (bits zero through 7) of the clock sequence in the same order of
674 Leach, et al. Standards Track [Page 12]
676 RFC 4122 A UUID URN Namespace July 2005
679 o Set the 6 least significant bits (bits zero through 5) of the
680 clock_seq_hi_and_reserved field to the 6 most significant bits
681 (bits 8 through 13) of the clock sequence in the same order of
684 o Set the two most significant bits (bits 6 and 7) of the
685 clock_seq_hi_and_reserved to zero and one, respectively.
687 o Set the node field to the 48-bit IEEE address in the same order of
688 significance as the address.
690 4.3. Algorithm for Creating a Name-Based UUID
692 The version 3 or 5 UUID is meant for generating UUIDs from "names"
693 that are drawn from, and unique within, some "name space". The
694 concept of name and name space should be broadly construed, and not
695 limited to textual names. For example, some name spaces are the
696 domain name system, URLs, ISO Object IDs (OIDs), X.500 Distinguished
697 Names (DNs), and reserved words in a programming language. The
698 mechanisms or conventions used for allocating names and ensuring
699 their uniqueness within their name spaces are beyond the scope of
702 The requirements for these types of UUIDs are as follows:
704 o The UUIDs generated at different times from the same name in the
705 same namespace MUST be equal.
707 o The UUIDs generated from two different names in the same namespace
708 should be different (with very high probability).
710 o The UUIDs generated from the same name in two different namespaces
711 should be different with (very high probability).
713 o If two UUIDs that were generated from names are equal, then they
714 were generated from the same name in the same namespace (with very
717 The algorithm for generating a UUID from a name and a name space are
720 o Allocate a UUID to use as a "name space ID" for all UUIDs
721 generated from names in that name space; see Appendix C for some
724 o Choose either MD5 [4] or SHA-1 [8] as the hash algorithm; If
725 backward compatibility is not an issue, SHA-1 is preferred.
730 Leach, et al. Standards Track [Page 13]
732 RFC 4122 A UUID URN Namespace July 2005
735 o Convert the name to a canonical sequence of octets (as defined by
736 the standards or conventions of its name space); put the name
737 space ID in network byte order.
739 o Compute the hash of the name space ID concatenated with the name.
741 o Set octets zero through 3 of the time_low field to octets zero
742 through 3 of the hash.
744 o Set octets zero and one of the time_mid field to octets 4 and 5 of
747 o Set octets zero and one of the time_hi_and_version field to octets
750 o Set the four most significant bits (bits 12 through 15) of the
751 time_hi_and_version field to the appropriate 4-bit version number
754 o Set the clock_seq_hi_and_reserved field to octet 8 of the hash.
756 o Set the two most significant bits (bits 6 and 7) of the
757 clock_seq_hi_and_reserved to zero and one, respectively.
759 o Set the clock_seq_low field to octet 9 of the hash.
761 o Set octets zero through five of the node field to octets 10
762 through 15 of the hash.
764 o Convert the resulting UUID to local byte order.
766 4.4. Algorithms for Creating a UUID from Truly Random or
767 Pseudo-Random Numbers
769 The version 4 UUID is meant for generating UUIDs from truly-random or
770 pseudo-random numbers.
772 The algorithm is as follows:
774 o Set the two most significant bits (bits 6 and 7) of the
775 clock_seq_hi_and_reserved to zero and one, respectively.
777 o Set the four most significant bits (bits 12 through 15) of the
778 time_hi_and_version field to the 4-bit version number from
781 o Set all the other bits to randomly (or pseudo-randomly) chosen
786 Leach, et al. Standards Track [Page 14]
788 RFC 4122 A UUID URN Namespace July 2005
791 See Section 4.5 for a discussion on random numbers.
793 4.5. Node IDs that Do Not Identify the Host
795 This section describes how to generate a version 1 UUID if an IEEE
796 802 address is not available, or its use is not desired.
798 One approach is to contact the IEEE and get a separate block of
799 addresses. At the time of writing, the application could be found at
800 <http://standards.ieee.org/regauth/oui/pilot-ind.html>, and the cost
803 A better solution is to obtain a 47-bit cryptographic quality random
804 number and use it as the low 47 bits of the node ID, with the least
805 significant bit of the first octet of the node ID set to one. This
806 bit is the unicast/multicast bit, which will never be set in IEEE 802
807 addresses obtained from network cards. Hence, there can never be a
808 conflict between UUIDs generated by machines with and without network
809 cards. (Recall that the IEEE 802 spec talks about transmission
810 order, which is the opposite of the in-memory representation that is
811 discussed in this document.)
813 For compatibility with earlier specifications, note that this
814 document uses the unicast/multicast bit, instead of the arguably more
815 correct local/global bit.
817 Advice on generating cryptographic-quality random numbers can be
818 found in RFC1750 [5].
820 In addition, items such as the computer's name and the name of the
821 operating system, while not strictly speaking random, will help
822 differentiate the results from those obtained by other systems.
824 The exact algorithm to generate a node ID using these data is system
825 specific, because both the data available and the functions to obtain
826 them are often very system specific. A generic approach, however, is
827 to accumulate as many sources as possible into a buffer, use a
828 message digest such as MD5 [4] or SHA-1 [8], take an arbitrary 6
829 bytes from the hash value, and set the multicast bit as described
832 5. Community Considerations
834 The use of UUIDs is extremely pervasive in computing. They comprise
835 the core identifier infrastructure for many operating systems
836 (Microsoft Windows) and applications (the Mozilla browser) and in
837 many cases, become exposed to the Web in many non-standard ways.
842 Leach, et al. Standards Track [Page 15]
844 RFC 4122 A UUID URN Namespace July 2005
847 This specification attempts to standardize that practice as openly as
848 possible and in a way that attempts to benefit the entire Internet.
850 6. Security Considerations
852 Do not assume that UUIDs are hard to guess; they should not be used
853 as security capabilities (identifiers whose mere possession grants
854 access), for example. A predictable random number source will
855 exacerbate the situation.
857 Do not assume that it is easy to determine if a UUID has been
858 slightly transposed in order to redirect a reference to another
859 object. Humans do not have the ability to easily check the integrity
860 of a UUID by simply glancing at it.
862 Distributed applications generating UUIDs at a variety of hosts must
863 be willing to rely on the random number source at all hosts. If this
864 is not feasible, the namespace variant should be used.
868 This document draws heavily on the OSF DCE specification for UUIDs.
869 Ted Ts'o provided helpful comments, especially on the byte ordering
870 section which we mostly plagiarized from a proposed wording he
871 supplied (all errors in that section are our responsibility,
874 We are also grateful to the careful reading and bit-twiddling of Ralf
875 S. Engelschall, John Larmouth, and Paul Thorpe. Professor Larmouth
876 was also invaluable in achieving coordination with ISO/IEC.
878 8. Normative References
880 [1] Zahn, L., Dineen, T., and P. Leach, "Network Computing
881 Architecture", ISBN 0-13-611674-4, January 1990.
883 [2] "DCE: Remote Procedure Call", Open Group CAE Specification C309,
884 ISBN 1-85912-041-5, August 1994.
886 [3] ISO/IEC 9834-8:2004 Information Technology, "Procedures for the
887 operation of OSI Registration Authorities: Generation and
888 registration of Universally Unique Identifiers (UUIDs) and their
889 use as ASN.1 Object Identifier components" ITU-T Rec. X.667,
892 [4] Rivest, R., "The MD5 Message-Digest Algorithm ", RFC 1321, April
898 Leach, et al. Standards Track [Page 16]
900 RFC 4122 A UUID URN Namespace July 2005
903 [5] Eastlake, D., 3rd, Schiller, J., and S. Crocker, "Randomness
904 Requirements for Security", BCP 106, RFC 4086, June 2005.
906 [6] Moats, R., "URN Syntax", RFC 2141, May 1997.
908 [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
909 Specifications: ABNF", RFC 2234, November 1997.
911 [8] National Institute of Standards and Technology, "Secure Hash
912 Standard", FIPS PUB 180-1, April 1995,
913 <http://www.itl.nist.gov/fipspubs/fip180-1.htm>.
954 Leach, et al. Standards Track [Page 17]
956 RFC 4122 A UUID URN Namespace July 2005
959 Appendix A. Appendix A - Sample Implementation
961 This implementation consists of 5 files: uuid.h, uuid.c, sysdep.h,
962 sysdep.c and utest.c. The uuid.* files are the system independent
963 implementation of the UUID generation algorithms described above,
964 with all the optimizations described above except efficient state
965 sharing across processes included. The code has been tested on Linux
966 (Red Hat 4.0) with GCC (2.7.2), and Windows NT 4.0 with VC++ 5.0.
967 The code assumes 64-bit integer support, which makes it much clearer.
969 All the following source files should have the following copyright
975 ** Copyright (c) 1990- 1993, 1996 Open Software Foundation, Inc.
976 ** Copyright (c) 1989 by Hewlett-Packard Company, Palo Alto, Ca. &
977 ** Digital Equipment Corporation, Maynard, Mass.
978 ** Copyright (c) 1998 Microsoft.
979 ** To anyone who acknowledges that this file is provided "AS IS"
980 ** without any express or implied warranty: permission to use, copy,
981 ** modify, and distribute this file for any purpose is hereby
982 ** granted without fee, provided that the above copyright notices and
983 ** this notice appears in all source code copies, and that none of
984 ** the names of Open Software Foundation, Inc., Hewlett-Packard
985 ** Company, Microsoft, or Digital Equipment Corporation be used in
986 ** advertising or publicity pertaining to distribution of the software
987 ** without specific, written prior permission. Neither Open Software
988 ** Foundation, Inc., Hewlett-Packard Company, Microsoft, nor Digital
989 ** Equipment Corporation makes any representations about the
990 ** suitability of this software for any purpose.
1000 unsigned16 time_mid;
1001 unsigned16 time_hi_and_version;
1002 unsigned8 clock_seq_hi_and_reserved;
1003 unsigned8 clock_seq_low;
1010 Leach, et al. Standards Track [Page 18]
1012 RFC 4122 A UUID URN Namespace July 2005
1015 /* uuid_create -- generate a UUID */
1016 int uuid_create(uuid_t * uuid);
1018 /* uuid_create_md5_from_name -- create a version 3 (MD5) UUID using a
1019 "name" from a "name space" */
1020 void uuid_create_md5_from_name(
1021 uuid_t *uuid, /* resulting UUID */
1022 uuid_t nsid, /* UUID of the namespace */
1023 void *name, /* the name from which to generate a UUID */
1024 int namelen /* the length of the name */
1027 /* uuid_create_sha1_from_name -- create a version 5 (SHA-1) UUID
1028 using a "name" from a "name space" */
1029 void uuid_create_sha1_from_name(
1031 uuid_t *uuid, /* resulting UUID */
1032 uuid_t nsid, /* UUID of the namespace */
1033 void *name, /* the name from which to generate a UUID */
1034 int namelen /* the length of the name */
1037 /* uuid_compare -- Compare two UUID's "lexically" and return
1038 -1 u1 is lexically before u2
1040 1 u1 is lexically after u2
1041 Note that lexical ordering is not temporal ordering!
1043 int uuid_compare(uuid_t *u1, uuid_t *u2);
1056 /* various forward declarations */
1057 static int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,
1059 static void write_state(unsigned16 clockseq, uuid_time_t timestamp,
1061 static void format_uuid_v1(uuid_t *uuid, unsigned16 clockseq,
1062 uuid_time_t timestamp, uuid_node_t node);
1066 Leach, et al. Standards Track [Page 19]
1068 RFC 4122 A UUID URN Namespace July 2005
1071 static void format_uuid_v3or5(uuid_t *uuid, unsigned char hash[16],
1073 static void get_current_time(uuid_time_t *timestamp);
1074 static unsigned16 true_random(void);
1076 /* uuid_create -- generator a UUID */
1077 int uuid_create(uuid_t *uuid)
1079 uuid_time_t timestamp, last_time;
1080 unsigned16 clockseq;
1082 uuid_node_t last_node;
1085 /* acquire system-wide lock so we're alone */
1087 /* get time, node ID, saved state from non-volatile storage */
1088 get_current_time(×tamp);
1089 get_ieee_node_identifier(&node);
1090 f = read_state(&clockseq, &last_time, &last_node);
1092 /* if no NV state, or if clock went backwards, or node ID
1093 changed (e.g., new network card) change clockseq */
1094 if (!f || memcmp(&node, &last_node, sizeof node))
1095 clockseq = true_random();
1096 else if (timestamp < last_time)
1099 /* save the state for next time */
1100 write_state(clockseq, timestamp, node);
1104 /* stuff fields into the UUID */
1105 format_uuid_v1(uuid, clockseq, timestamp, node);
1109 /* format_uuid_v1 -- make a UUID from the timestamp, clockseq,
1111 void format_uuid_v1(uuid_t* uuid, unsigned16 clock_seq,
1112 uuid_time_t timestamp, uuid_node_t node)
1114 /* Construct a version 1 uuid with the information we've gathered
1115 plus a few constants. */
1116 uuid->time_low = (unsigned long)(timestamp & 0xFFFFFFFF);
1117 uuid->time_mid = (unsigned short)((timestamp >> 32) & 0xFFFF);
1118 uuid->time_hi_and_version =
1122 Leach, et al. Standards Track [Page 20]
1124 RFC 4122 A UUID URN Namespace July 2005
1127 (unsigned short)((timestamp >> 48) & 0x0FFF);
1128 uuid->time_hi_and_version |= (1 << 12);
1129 uuid->clock_seq_low = clock_seq & 0xFF;
1130 uuid->clock_seq_hi_and_reserved = (clock_seq & 0x3F00) >> 8;
1131 uuid->clock_seq_hi_and_reserved |= 0x80;
1132 memcpy(&uuid->node, &node, sizeof uuid->node);
1135 /* data type for UUID generator persistent state */
1137 uuid_time_t ts; /* saved timestamp */
1138 uuid_node_t node; /* saved node ID */
1139 unsigned16 cs; /* saved clock sequence */
1142 static uuid_state st;
1144 /* read_state -- read UUID generator state from non-volatile store */
1145 int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,
1148 static int inited = 0;
1151 /* only need to read state once per boot */
1153 fp = fopen("state", "rb");
1156 fread(&st, sizeof st, 1, fp);
1166 /* write_state -- save UUID generator state back to non-volatile
1168 void write_state(unsigned16 clockseq, uuid_time_t timestamp,
1171 static int inited = 0;
1172 static uuid_time_t next_save;
1178 Leach, et al. Standards Track [Page 21]
1180 RFC 4122 A UUID URN Namespace July 2005
1184 next_save = timestamp;
1188 /* always save state to volatile shared state */
1192 if (timestamp >= next_save) {
1193 fp = fopen("state", "wb");
1194 fwrite(&st, sizeof st, 1, fp);
1196 /* schedule next save for 10 seconds from now */
1197 next_save = timestamp + (10 * 10 * 1000 * 1000);
1201 /* get-current_time -- get time as 60-bit 100ns ticks since UUID epoch.
1202 Compensate for the fact that real clock resolution is
1204 void get_current_time(uuid_time_t *timestamp)
1206 static int inited = 0;
1207 static uuid_time_t time_last;
1208 static unsigned16 uuids_this_tick;
1209 uuid_time_t time_now;
1212 get_system_time(&time_now);
1213 uuids_this_tick = UUIDS_PER_TICK;
1218 get_system_time(&time_now);
1220 /* if clock reading changed since last UUID generated, */
1221 if (time_last != time_now) {
1222 /* reset count of uuids gen'd with this clock reading */
1223 uuids_this_tick = 0;
1224 time_last = time_now;
1227 if (uuids_this_tick < UUIDS_PER_TICK) {
1234 Leach, et al. Standards Track [Page 22]
1236 RFC 4122 A UUID URN Namespace July 2005
1239 /* going too fast for our clock; spin */
1241 /* add the count of uuids to low order bits of the clock reading */
1242 *timestamp = time_now + uuids_this_tick;
1245 /* true_random -- generate a crypto-quality random number.
1246 **This sample doesn't do that.** */
1247 static unsigned16 true_random(void)
1249 static int inited = 0;
1250 uuid_time_t time_now;
1253 get_system_time(&time_now);
1254 time_now = time_now / UUIDS_PER_TICK;
1255 srand((unsigned int)
1256 (((time_now >> 32) ^ time_now) & 0xffffffff));
1263 /* uuid_create_md5_from_name -- create a version 3 (MD5) UUID using a
1264 "name" from a "name space" */
1265 void uuid_create_md5_from_name(uuid_t *uuid, uuid_t nsid, void *name,
1269 unsigned char hash[16];
1272 /* put name space ID in network byte order so it hashes the same
1273 no matter what endian machine we're on */
1275 net_nsid.time_low = htonl(net_nsid.time_low);
1276 net_nsid.time_mid = htons(net_nsid.time_mid);
1277 net_nsid.time_hi_and_version = htons(net_nsid.time_hi_and_version);
1280 MD5Update(&c, &net_nsid, sizeof net_nsid);
1281 MD5Update(&c, name, namelen);
1284 /* the hash is in network byte order at this point */
1285 format_uuid_v3or5(uuid, hash, 3);
1290 Leach, et al. Standards Track [Page 23]
1292 RFC 4122 A UUID URN Namespace July 2005
1295 void uuid_create_sha1_from_name(uuid_t *uuid, uuid_t nsid, void *name,
1299 unsigned char hash[20];
1302 /* put name space ID in network byte order so it hashes the same
1303 no matter what endian machine we're on */
1305 net_nsid.time_low = htonl(net_nsid.time_low);
1306 net_nsid.time_mid = htons(net_nsid.time_mid);
1307 net_nsid.time_hi_and_version = htons(net_nsid.time_hi_and_version);
1310 SHA1_Update(&c, &net_nsid, sizeof net_nsid);
1311 SHA1_Update(&c, name, namelen);
1312 SHA1_Final(hash, &c);
1314 /* the hash is in network byte order at this point */
1315 format_uuid_v3or5(uuid, hash, 5);
1318 /* format_uuid_v3or5 -- make a UUID from a (pseudo)random 128-bit
1320 void format_uuid_v3or5(uuid_t *uuid, unsigned char hash[16], int v)
1322 /* convert UUID to local byte order */
1323 memcpy(uuid, hash, sizeof *uuid);
1324 uuid->time_low = ntohl(uuid->time_low);
1325 uuid->time_mid = ntohs(uuid->time_mid);
1326 uuid->time_hi_and_version = ntohs(uuid->time_hi_and_version);
1328 /* put in the variant and version bits */
1329 uuid->time_hi_and_version &= 0x0FFF;
1330 uuid->time_hi_and_version |= (v << 12);
1331 uuid->clock_seq_hi_and_reserved &= 0x3F;
1332 uuid->clock_seq_hi_and_reserved |= 0x80;
1335 /* uuid_compare -- Compare two UUID's "lexically" and return */
1336 #define CHECK(f1, f2) if (f1 != f2) return f1 < f2 ? -1 : 1;
1337 int uuid_compare(uuid_t *u1, uuid_t *u2)
1341 CHECK(u1->time_low, u2->time_low);
1342 CHECK(u1->time_mid, u2->time_mid);
1346 Leach, et al. Standards Track [Page 24]
1348 RFC 4122 A UUID URN Namespace July 2005
1351 CHECK(u1->time_hi_and_version, u2->time_hi_and_version);
1352 CHECK(u1->clock_seq_hi_and_reserved, u2->clock_seq_hi_and_reserved);
1353 CHECK(u1->clock_seq_low, u2->clock_seq_low)
1354 for (i = 0; i < 6; i++) {
1355 if (u1->node[i] < u2->node[i])
1357 if (u1->node[i] > u2->node[i])
1368 /* remove the following define if you aren't running WIN32 */
1372 #include <windows.h>
1374 #include <sys/types.h>
1375 #include <sys/time.h>
1376 #include <sys/sysinfo.h>
1380 /* change to point to where MD5 .h's live; RFC 1321 has sample
1384 /* set the following to the number of 100ns ticks of the actual
1385 resolution of your system's clock */
1386 #define UUIDS_PER_TICK 1024
1388 /* Set the following to a calls to get and release a global lock */
1392 typedef unsigned long unsigned32;
1393 typedef unsigned short unsigned16;
1394 typedef unsigned char unsigned8;
1395 typedef unsigned char byte;
1397 /* Set this to what your compiler uses for 64-bit data type */
1402 Leach, et al. Standards Track [Page 25]
1404 RFC 4122 A UUID URN Namespace July 2005
1407 #define unsigned64_t unsigned __int64
1410 #define unsigned64_t unsigned long long
1411 #define I64(C) C##LL
1414 typedef unsigned64_t uuid_time_t;
1419 void get_ieee_node_identifier(uuid_node_t *node);
1420 void get_system_time(uuid_time_t *uuid_time);
1421 void get_random_info(char seed[16]);
1430 /* system dependent call to get IEEE node ID.
1431 This sample implementation generates a random node ID. */
1432 void get_ieee_node_identifier(uuid_node_t *node)
1435 static uuid_node_t saved_node;
1440 fp = fopen("nodeid", "rb");
1442 fread(&saved_node, sizeof saved_node, 1, fp);
1446 get_random_info(seed);
1448 memcpy(&saved_node, seed, sizeof saved_node);
1449 fp = fopen("nodeid", "wb");
1451 fwrite(&saved_node, sizeof saved_node, 1, fp);
1458 Leach, et al. Standards Track [Page 26]
1460 RFC 4122 A UUID URN Namespace July 2005
1469 /* system dependent call to get the current system time. Returned as
1470 100ns ticks since UUID epoch, but resolution may be less than
1474 void get_system_time(uuid_time_t *uuid_time)
1476 ULARGE_INTEGER time;
1478 /* NT keeps time in FILETIME format which is 100ns ticks since
1479 Jan 1, 1601. UUIDs use time in 100ns ticks since Oct 15, 1582.
1480 The difference is 17 Days in Oct + 30 (Nov) + 31 (Dec)
1481 + 18 years and 5 leap days. */
1482 GetSystemTimeAsFileTime((FILETIME *)&time);
1485 (unsigned __int64) (1000*1000*10) // seconds
1486 * (unsigned __int64) (60 * 60 * 24) // days
1487 * (unsigned __int64) (17+30+31+365*18+5); // # of days
1488 *uuid_time = time.QuadPart;
1491 /* Sample code, not for use in production; see RFC 1750 */
1492 void get_random_info(char seed[16])
1502 char hostname[MAX_COMPUTERNAME_LENGTH + 1];
1506 GlobalMemoryStatus(&r.m);
1507 GetSystemInfo(&r.s);
1508 GetSystemTimeAsFileTime(&r.t);
1509 QueryPerformanceCounter(&r.pc);
1510 r.tc = GetTickCount();
1514 Leach, et al. Standards Track [Page 27]
1516 RFC 4122 A UUID URN Namespace July 2005
1519 r.l = MAX_COMPUTERNAME_LENGTH + 1;
1520 GetComputerName(r.hostname, &r.l);
1521 MD5Update(&c, &r, sizeof r);
1527 void get_system_time(uuid_time_t *uuid_time)
1531 gettimeofday(&tp, (struct timezone *)0);
1533 /* Offset between UUID formatted times and Unix formatted times.
1534 UUID UTC base time is October 15, 1582.
1535 Unix base time is January 1, 1970.*/
1536 *uuid_time = ((unsigned64)tp.tv_sec * 10000000)
1537 + ((unsigned64)tp.tv_usec * 10)
1538 + I64(0x01B21DD213814000);
1541 /* Sample code, not for use in production; see RFC 1750 */
1542 void get_random_info(char seed[16])
1553 gettimeofday(&r.t, (struct timezone *)0);
1554 gethostname(r.hostname, 256);
1555 MD5Update(&c, &r, sizeof r);
1570 Leach, et al. Standards Track [Page 28]
1572 RFC 4122 A UUID URN Namespace July 2005
1575 uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */
1579 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
1582 /* puid -- print a UUID */
1587 printf("%8.8x-%4.4x-%4.4x-%2.2x%2.2x-", u.time_low, u.time_mid,
1588 u.time_hi_and_version, u.clock_seq_hi_and_reserved,
1590 for (i = 0; i < 6; i++)
1591 printf("%2.2x", u.node[i]);
1595 /* Simple driver for UUID generator */
1596 void main(int argc, char **argv)
1602 printf("uuid_create(): "); puid(u);
1604 f = uuid_compare(&u, &u);
1605 printf("uuid_compare(u,u): %d\n", f); /* should be 0 */
1606 f = uuid_compare(&u, &NameSpace_DNS);
1607 printf("uuid_compare(u, NameSpace_DNS): %d\n", f); /* s.b. 1 */
1608 f = uuid_compare(&NameSpace_DNS, &u);
1609 printf("uuid_compare(NameSpace_DNS, u): %d\n", f); /* s.b. -1 */
1610 uuid_create_md5_from_name(&u, NameSpace_DNS, "www.widgets.com", 15);
1611 printf("uuid_create_md5_from_name(): "); puid(u);
1614 Appendix B. Appendix B - Sample Output of utest
1616 uuid_create(): 7d444840-9dc0-11d1-b245-5ffdce74fad2
1617 uuid_compare(u,u): 0
1618 uuid_compare(u, NameSpace_DNS): 1
1619 uuid_compare(NameSpace_DNS, u): -1
1620 uuid_create_md5_from_name(): e902893a-9d22-3c7e-a7b8-d6e313b71d9f
1626 Leach, et al. Standards Track [Page 29]
1628 RFC 4122 A UUID URN Namespace July 2005
1631 Appendix C. Appendix C - Some Name Space IDs
1633 This appendix lists the name space IDs for some potentially
1634 interesting name spaces, as initialized C structures and in the
1635 string representation defined above.
1637 /* Name string is a fully-qualified domain name */
1638 uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */
1642 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
1645 /* Name string is a URL */
1646 uuid_t NameSpace_URL = { /* 6ba7b811-9dad-11d1-80b4-00c04fd430c8 */
1650 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
1653 /* Name string is an ISO OID */
1654 uuid_t NameSpace_OID = { /* 6ba7b812-9dad-11d1-80b4-00c04fd430c8 */
1658 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
1661 /* Name string is an X.500 DN (in DER or a text output format) */
1662 uuid_t NameSpace_X500 = { /* 6ba7b814-9dad-11d1-80b4-00c04fd430c8 */
1666 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
1682 Leach, et al. Standards Track [Page 30]
1684 RFC 4122 A UUID URN Namespace July 2005
1695 Phone: +1 425-882-8080
1696 EMail: paulle@microsoft.com
1700 Refactored Networks, LLC
1706 Phone: +1-678-581-9656
1707 EMail: michael@refactored-networks.com
1708 URI: http://www.refactored-networks.com
1712 DataPower Technology, Inc.
1717 Phone: +1 617-864-0455
1718 EMail: rsalz@datapower.com
1719 URI: http://www.datapower.com
1738 Leach, et al. Standards Track [Page 31]
1740 RFC 4122 A UUID URN Namespace July 2005
1743 Full Copyright Statement
1745 Copyright (C) The Internet Society (2005).
1747 This document is subject to the rights, licenses and restrictions
1748 contained in BCP 78, and except as set forth therein, the authors
1749 retain all their rights.
1751 This document and the information contained herein are provided on an
1752 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
1753 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
1754 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
1755 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
1756 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
1757 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
1759 Intellectual Property
1761 The IETF takes no position regarding the validity or scope of any
1762 Intellectual Property Rights or other rights that might be claimed to
1763 pertain to the implementation or use of the technology described in
1764 this document or the extent to which any license under such rights
1765 might or might not be available; nor does it represent that it has
1766 made any independent effort to identify any such rights. Information
1767 on the procedures with respect to rights in RFC documents can be
1768 found in BCP 78 and BCP 79.
1770 Copies of IPR disclosures made to the IETF Secretariat and any
1771 assurances of licenses to be made available, or the result of an
1772 attempt made to obtain a general license or permission for the use of
1773 such proprietary rights by implementers or users of this
1774 specification can be obtained from the IETF on-line IPR repository at
1775 http://www.ietf.org/ipr.
1777 The IETF invites any interested party to bring to its attention any
1778 copyrights, patents or patent applications, or other proprietary
1779 rights that may cover technology that may be required to implement
1780 this standard. Please address the information to the IETF at ietf-
1785 Funding for the RFC Editor function is currently provided by the
1794 Leach, et al. Standards Track [Page 32]