* Identifiers
** Problem description
   Identifiers can be integers, strings or other objects. They should
   be unique.
** Approach 1: integers
   Integers are somewhat easy to remember, but also include
   predictable growth, which might allow access to guessed hacking
   (obivously proper permissions should prevent this).
** Approach 2: random uuids
   UUIDs are 128 bit integers. Python supports uuid.uuid4() for random
   uuids.
** Approach 3: IPv6 addresses
   uncloud heavily depends on IPv6 in the first place. uncloud could
   use a /48 to identify all objects. Objects that have IPv6 addresses
   on their own, don't need to draw from the system /48.
*** Possible Subnetworks
    Assuming uncloud uses a /48 to represent all resources.

    | Network         | Name            | Description                                  |
    |-----------------+-----------------+----------------------------------------------|
    | 2001:db8::/48   | uncloud network | All identifiers drawn from here              |
    | 2001:db8:1::/64 | VM network      | Every VM has an IPv6 address in this network |
    | 2001:db8:2::/64 | Bill network    | Every bill has an IPv6 address               |
    | 2001:db8:3::/64 | Order network   | Every order has an IPv6 address              |
    | 2001:db8:5::/64 | Product network | Every product (?) has an IPv6 address        |
    | 2001:db8:4::/64 | Disk network    | Every disk is identified                     |

*** Tests
    [15:47:37] black3.place6:~# rbd create -s 10G ssd/2a0a:e5c0:1::8