Now with the IANA pool getting depleted in a few moths it is interesting to take a look at what will happen afterwards. One source of IPv4 addresses that will come into use is the so called Various Pool. The history of the various pool is that prior to IPv4 classless Inter Domain Routing the class-B and class-C networks was allocated directly to end organizations from a set of IPv4 /8 blocks. These blocks are still around and got quite a bit of free IPv4 space in them (about 7.5 x /8). When looking at the IANA statistics file they show up as LEGACY blocks.

There is an agreement from 2008 between the NRO and IANA on how these blocks will be distributed amongst the RIRs. The idea is that they should be distributed to the RIRs according to this letter. The intention of the agreement appears to have been to distribute the blocks evenly. The XLS spreadsheet that is attached to the letter shows that they did a pretty good job making sure that all RIRs got the same number of addresses. 7.5 x /8 sounds good, right? However, there are issues with these blocks and things have happened since 2008. With the IPv4 depletion date around the corner, it is time to take a new look at the status of the various pool.

The 188/8 block
The 188/8 block was supposed to go to RIPE post IANA depletion. However, RIPE has already used up most of this block as I noted in March 2009

188/8 was completely empty except for one /16 allocating prior to RIPE starting to use it lately. Because RIPE already used up most of 188/8 they will get significantly lesser IPv4 addresses than the other RIRs when the various pool is divided between the RIRs.

The 191/8 block
The 191/8 block will go to LACNIC. An interesting thing with this block is that it is totally unused. The 191.255/16 network used to be reserved by RFC3330 but was freed up when RFC5735 was published in the beginning of 2010. So LACNIC gained 65k extra addresses, no big deal. But should this block still be in the various pool since it is empty?

The 196/8 block
It appears that the NRO and IANA forgot to include the 196/8 in their calculations. This block contains the equivalent to 0.71 x /8 or around 12 million IPv4 addresses in nice and large contiguous blocks. It has historically been used by several different RIRs but lately it delegations from this block has predominantly been made by AfriNIC who also handles the reverse DNS and whois for the block.

Personally, I’m all for giving less developed regions more IPv4 addresses. However, at some point it becomes very wasteful. AfriNIC already have (or will get) IPv4 addresses to cover their demand until the year of 2015 even with an exponential growth of the demand in the region. Five years from now I hope that IPv6 will be the predominant network protocol on the Internet and the value of an IPv4 address will be pretty low. Giving AfriNIC more IPv4 will not really help because they will not be able to communicate with any IPv6 hosts unless they deploy IPv6. However, let’s assume for now that this block will be given to AfriNIC.

The various pool are remains from /8 blocks used for class-B or class-C delegations prior to CIDR. They are therefore chopped up in smaller chunks and the free space is non-contiguous. Large service providers would rather get larger chunks of IPv4 addresses that small gravel to simplify maintenance and keep down the size of the routing table. Here is a list of the blocks that are in decent shape.
APNIC: 171/8 usable, 153/8 upper half free, 139/8 Some large free blocks
ARIN: 162/2 upper half mostly free, 172/8 mostly usable
LACNIC: 152/8 some usable blocks, 191/8 totally free
AfriNIC: 154/8 mostly free, 156/8 large chunks free on the upper half.
RIPE: 151/8 some large blocks free, with the biggest being 2 million addresses.

Unless something changes, the number of IPv4 addresses each RIR gets from the various pool will be:
RIPE: 0.67 x /8
LAC : 1.55 x /8
ARIN: 1.54 x /8
APNI: 1.54 x /8
AFRI: 2.25 x /8

The issues with 188/8, 191/8 and 196/8 as discussed above are the reason why the distribution is somewhat skewed. But how much “gravel” is there in those block. An interesting exercise is to remove all of the small blocks (smaller than 100k addresses). If we do that, the picture looks somewhat different:
RIPE: 0.33 x /8
LAC : 1.27 x /8
ARIN: 1.06 x /8
APNI: 1.27 x /8
AFRI: 2.01 x /8

As you can see, RIPE and ARIN appears to have gotten the most of the fragmented blocks from the various pool. If you are a large service provider you need to be aware of the fact that you might not be able to get large contiguous blocks of IPv4 addresses as we move closer to RIR depletion.

/written by Stephan Lagerholm (C) 2010