mapping arbitrary IPv6 addresses to individual RIRs (ARIN, RIPE, etc.)

Question

It's easy to map IPv4 addresses to their controlling RIR (ARIN, RIPE, etc.) since v4 addresses are handed out by IANA in blocks of /8 . I can write a function that takes an arbitrary IPv4 address and figures out the proper RIR simply by examining the first eight bits of that address.

According to http://www.iana.org/assignments/ipv6-unicast-address-assignments/ipv6-unicast-address-assignments.txt though, global unicast IPv6 addresses are being handed out in blocks of different sizes. I can't see any rhyme or reason for why these blocks have been allocated in the sizes they have. This might make it a chore to write an IPv6 version of the above function.

Is there an easy way to tell which (global unicast) IPv6 address belongs to which RIR? Or will I have to iterate over all assigned netblocks and see if my address is covered by one of them?

thanks!

Answer 1

The only way is to match with the list you mentionned: parse the list and match your address with the entries. There should be exactly one entry which matches; this is your result.

Why the blocks have different sizes? Well, I think that has historical reasons. First, only 2001: addresses were handed out; the block sizes assigned was probably die to varying needs of the customers. Soon, they noticed that a /23 is too small. Eventually (at around 2006), they assigned a /12 to every RIR which now must look how to get along with that. That should last for a while; if they all are used, new blocks will be assigned.