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Ben Ramsey
58 lines
2.5 KiB
ReStructuredText
58 lines
2.5 KiB
ReStructuredText
.. _rfc4122:
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==================================
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RFC 9562 (formerly RFC 4122) UUIDs
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==================================
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.. toctree::
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:titlesonly:
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:hidden:
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rfc4122/version1
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rfc4122/version2
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rfc4122/version3
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rfc4122/version4
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rfc4122/version5
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rfc4122/version6
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rfc4122/version7
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rfc4122/version8
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`RFC 9562`_ (formerly `RFC 4122`_) defines eight versions of UUIDs. Each version has different generation algorithms and
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properties. Which one you choose depends on your use-case. You can find out more about their applications on the
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specific page for that version.
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Version 1: Gregorian Time
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This version of UUID combines a timestamp, node value (in the form of a MAC address from the local computer's
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network interface), and a clock sequence to ensure uniqueness. For more details, see :doc:`rfc4122/version1`.
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Version 2: DCE Security
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This version of UUID is the same as Version 1, except the ``clock_seq_low`` field is replaced with a *local domain*
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and the ``time_low`` field is replaced with a *local identifier*. For more details, see :doc:`rfc4122/version2`.
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Version 3: Name-based (MD5)
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This version of UUID hashes together a namespace and a name to create a deterministic UUID. The hashing algorithm
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used is MD5. For more details, see :doc:`rfc4122/version3`.
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Version 4: Random
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This version creates a UUID using truly-random or pseudo-random numbers. For more details, see :doc:`rfc4122/version4`.
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Version 5: Named-based (SHA-1)
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This version of UUID hashes together a namespace and a name to create a deterministic UUID. The hashing algorithm
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used is SHA-1. For more details, see :doc:`rfc4122/version5`.
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Version 6: Reordered Gregorian Time
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This version of UUID combines the features of a :ref:`version 1 UUID <rfc4122.version1>` with a *monotonically
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increasing* UUID. For more details, see :ref:`rfc4122.version6`.
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Version 7: Unix Epoch Time
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This version of UUID combines a timestamp--based on milliseconds elapsed since the Unix Epoch--and random bytes to
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create a monotonically increasing, sortable UUID without the privacy and entropy concerns associated with version 1
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and version 6 UUIDs. For more details, see :ref:`rfc4122.version7`.
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Version 8: Implementation-Specific, Custom Format
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This version of UUID allows applications to generate custom identifiers in an RFC-compatible format. For more
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details, see :doc:`rfc4122/version8`.
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.. _RFC 4122: https://www.rfc-editor.org/rfc/rfc4122
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.. _RFC 9562: https://www.rfc-editor.org/rfc/rfc9562
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