Geoff points out in his document that distribution of the "centrally assigned" Unique Local IPv6 Unicast Addresses space FC00::/8 is tricky if the registries all have to coordinate with each other when selection occurs.
Also, assigning address blocks seems undesirable because the desire to cripple the aggregability of this address space and hence cripple its global routability.
A mechanism for partitioning the available space amongst a set of registries that isn't "block-like" could therefore be a useful thing.
A suggestion: IANA can allocate vectors of numbers to each registry that span the entire address space.
For example: In the allocatable range 0-2^41, each set of numbers described by
S = { n < 0-2^41: n = V + k*G where k=0,1,2, ...}
where:
G is a largish number that partitions the available space, and
V (< G) identifies the vector that is allocated to a registry
are non-overlapping, non-aggregable allocations.
IANA would allocate integer Vs to registries and keep a database of the Vs already assigned. The Vs can be sequentially allocated. Registries allocate from the S-es (vectors of numbers) generated by the Vs they are given without the need to coordinate with each other. The value G controls the size of the vector (I'm not sure off-hand what a sensible number might be).
Technically, a router could work out V by examining the address (ie the_41_bit_part mod G will be the same for all allocations in the same vector) and thus perform aggregation by routing on the value of V, however if G is not a power of 2 (perhaps a prime) this would be an expensive operation.
- aidan
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