guid - UUID format: 8-4-4-4-12 - Why? -


why uuid's presented in format "8-4-4-4-12" (digits)? i've had around reason can't find decision calls it.

example of uuid formatted hex string: 58d5e212-165b-4ca0-909b-c86b9cee0111

it's separated time, version, clock_seq_hi, clock_seq_lo, node, indicated in followoing rfc.

from ietf rfc4122:

4.1.2.  layout , byte order     minimize confusion bit assignments within octets, uuid    record definition defined in terms of fields    integral numbers of octets.  fields presented    significant 1 first.     field                  data type     octet  note                                         #     time_low               unsigned 32   0-3    low field of                           bit integer          timestamp     time_mid               unsigned 16   4-5    middle field of                           bit integer          timestamp     time_hi_and_version    unsigned 16   6-7    high field of                           bit integer          timestamp multiplexed                                                version number       clock_seq_hi_and_rese  unsigned 8    8      high field of    rved                   bit integer          clock sequence                                                multiplexed                                                variant     clock_seq_low          unsigned 8    9      low field of                           bit integer          clock sequence     node                   unsigned 48   10-15  spatially unique                           bit integer          node identifier     in absence of explicit application or presentation protocol    specification contrary, uuid encoded 128-bit object,    follows:     fields encoded 16 octets, sizes , order of    fields defined above, , each field encoded    significant byte first (known network byte order).  note    field names, particularly multiplexed fields, follow historical    practice.     0                   1                   2                   3     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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |                          time_low                             |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |       time_mid                |         time_hi_and_version   |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |clk_seq_hi_res |  clk_seq_low  |         node (0-1)            |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |                         node (2-5)                            |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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