Talk:Universally unique identifier: Difference between revisions
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== Textual representation == |
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== MAC and clock - bad ideas? == |
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Move this section up before the Variants and special cases section [[User:Theking2|Theking2]] ([[User talk:Theking2|talk]]) 13:17, 2 March 2024 (UTC) |
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== What are the different variants of Version 4 UUID's used for? == |
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It is common to copy MAC addresses over from one NIC to another in clustered environments. So make sure to use the factory MAC and not the MAC visible on the network. |
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From what I can determine, Version 4 UUID's -- the random kind -- have four variants, signified by the 17th hex digit being one of "8", "9", " a", or "b" (which is how I will refer to each variant here). |
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The clock may generate (improbable) duplicates if it is set backwards. I already had to adjust the clock of a server backwards, probably due to a HW glitch. A rogue NTP server might be used as an attack vector. |
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What are these four different variants <i><b>for</b></i>? How are they <i><b>used</b></i>? What determines the use of (say) variant "a" rather than variant "8"? |
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Version 1 and 2 also have poor entropy. This is not necessarily a disadvantage. A more or less sequential nature of UUIDs may be a wanted feature <ref>https://www.2ndquadrant.com/en/blog/sequential-uuid-generators/</ref>. |
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I'm writing a program to generate these UUID's pseudorandomly, and I don't want to make some kind of ghastly error by providing the wrong type of UUID! Is there a reason why one would use one v4 variant and not another? Are some v4 variants more apprpriate for some uses, and others for other uses? The ONLY document I've yet come across that addresses this issue says (in relevant part): |
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The clock has the advantage to allow to reconstitute roughly in which order the UUIDs have been generated - if you can trust the clock. |
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<blockquote><i>"...Version-4, variant-1 UUIDs are used in the game Minecraft... Version-4, variant-2 is called a "GUID" on Microsoft systems..."</i> |
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BTW, version 6 is on the way: <ref>https://tools.ietf.org/html/draft-peabody-dispatch-new-uuid-format-00 |
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</ref> |
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(Source: https://www.uuidtools.com/uuid-versions-explained, Retrieved: Fri., 30-Sep-2022 at 08:43:17pm -0400 UTC.)</blockquote> |
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[[User:Stonux|Stonux]] ([[User talk:Stonux|talk]]) 14:11, 10 July 2020 (UTC) |
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However, this leaves unanswered qustions. First (and most obvious) is, what about variants 3 and 4 (what I call "a" and "b" above)? |
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{{reflist-talk}} |
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Also, the phrases "are used in" and "is called a" don't tell me whether these variants are <i>exclusively reserved</i> for these uses, or if it is permitted to use them for other, additional, purposes as well. |
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== UUID generator: why only uuidgen.org allowed? == |
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The main Wikipedia article doesn't even remotely <i><b>begin</b></i> to even <i><b>touch</b></i> upon this question... |
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While [https://www.uuidgenerator.net/ this generator] is [https://www.itu.int/en/ITU-T/asn1/Pages/UUID/uuids.aspx recommended by ITU-T], I don't see uuidgen.org being recommended by any authorities (ITU-T, ISO, IETF). Only thing in that website is "@Accelery", which is a twitter account with only one tweet: "Online UUID generators seem stuck in the past, so we made a new one." That's it, no more information is given. Very flimsy. How can we trust that? How superior is that from the one recommended by ITU-T? Any users of that tool can comment? There was a comment {{code|<<nowiki>!--</nowiki>Do not add any more GUID generator web sites; they will be removed.}} which discouraged editors to add alternative UUID generators. That's [[WP:PROMO|advertising]], in my opinion. Therefore I removed it and replaced by the ITU-T one. [[User:Feelthhis|Feelthhis]] ([[User talk:Feelthhis|talk]]) 04:00, 19 December 2020 (UTC) |
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Guidance? Help? Please? |
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== DOCTYPE Puzzle == |
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== Citation needed == |
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Readers of this page may be interested in thw following discussion: |
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* [[Wikipedia:Reference desk/Computing#DOCTYPE Puzzle]] |
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--[[User:Guy Macon|Guy Macon]] ([[User talk:Guy Macon|talk]]) 22:37, 1 June 2021 (UTC) |
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The text says a citation for DomainOS is needed. Here are two: |
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== When Microsoft started using UUIDs == |
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Leach, P. J., Levine, P.H., Hamilton, J. A., Stumpf, B.L., |
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To help fill in the history for when Microsoft started using UUIDs (the "when" question is flagged in the article), I have a bit of information that might help someone search for the answer. |
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"UIDs as Internal Names in a Distributed File System," |
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in Proceedings ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing, |
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Ottawa, Ont., Aug. 18-20, 1982, pp. 34-41. |
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Leach, P. J., Levine, P.H., Douros, B. D., Hamilton, J. A., Nelson, D. L., Stumpf, B.L., |
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I attended a Microsoft conference at the Redmond campus in 1995 where a presenter gave information about UUIDs, how they are essentially unique, and that Microsoft was going to be using them. |
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"The Architecture of an Integrated Local Network," |
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IEEE Journal on Selected Areas in Communications, |
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v.SAC-1, n.5, Nov. 1983, pp. 842-857. |
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The first is more about UIDs in DomainOS, the second is about the OS overall. [[User:Paul Jay Seattle|Paul Jay Seattle]] ([[User talk:Paul Jay Seattle|talk]]) 23:18, 15 September 2023 (UTC) |
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That's not enough to put into the article, obviously, but maybe it'll help give a timeline if someone is researching this. <!-- Template:Unsigned --><span class="autosigned" style="font-size:85%;">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Chris uvic|Chris uvic]] ([[User talk:Chris uvic#top|talk]] • [[Special:Contributions/Chris uvic|contribs]]) 18:20, 30 June 2021 (UTC)</span> <!--Autosigned by SineBot--> |
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Textual representation
[edit]Move this section up before the Variants and special cases section Theking2 (talk) 13:17, 2 March 2024 (UTC)
What are the different variants of Version 4 UUID's used for?
[edit]From what I can determine, Version 4 UUID's -- the random kind -- have four variants, signified by the 17th hex digit being one of "8", "9", " a", or "b" (which is how I will refer to each variant here).
What are these four different variants for? How are they used? What determines the use of (say) variant "a" rather than variant "8"?
I'm writing a program to generate these UUID's pseudorandomly, and I don't want to make some kind of ghastly error by providing the wrong type of UUID! Is there a reason why one would use one v4 variant and not another? Are some v4 variants more apprpriate for some uses, and others for other uses? The ONLY document I've yet come across that addresses this issue says (in relevant part):
"...Version-4, variant-1 UUIDs are used in the game Minecraft... Version-4, variant-2 is called a "GUID" on Microsoft systems..." (Source: https://www.uuidtools.com/uuid-versions-explained, Retrieved: Fri., 30-Sep-2022 at 08:43:17pm -0400 UTC.)
However, this leaves unanswered qustions. First (and most obvious) is, what about variants 3 and 4 (what I call "a" and "b" above)?
Also, the phrases "are used in" and "is called a" don't tell me whether these variants are exclusively reserved for these uses, or if it is permitted to use them for other, additional, purposes as well.
The main Wikipedia article doesn't even remotely begin to even touch upon this question...
Guidance? Help? Please?
Citation needed
[edit]The text says a citation for DomainOS is needed. Here are two:
Leach, P. J., Levine, P.H., Hamilton, J. A., Stumpf, B.L., "UIDs as Internal Names in a Distributed File System," in Proceedings ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing, Ottawa, Ont., Aug. 18-20, 1982, pp. 34-41.
Leach, P. J., Levine, P.H., Douros, B. D., Hamilton, J. A., Nelson, D. L., Stumpf, B.L., "The Architecture of an Integrated Local Network," IEEE Journal on Selected Areas in Communications, v.SAC-1, n.5, Nov. 1983, pp. 842-857.
The first is more about UIDs in DomainOS, the second is about the OS overall. Paul Jay Seattle (talk) 23:18, 15 September 2023 (UTC)