Boom and Bust in IP Address Space Land

Dave Reed on e2e notes a very interesting item - ARIN has announced that migration to IPv6 is now mandatory for allocation of contiguous IP address space. "I still remember debating variable length addressing and source routing in the 1970's TCP design days, and being told that 4 Thousand Million addresses would be enough for the life of the Internet" Dave crows. But is this an accurate "read"? (I know Dave won't mind the pun, as he's heard it many times before).

As I commented on e2e, I remember that debate as well. But the whole genesis of why 32 bits was good enough was an (underjustified) view on the use of networks rather than an understanding of how sparse addresses were actually employed. Everybody knows hash tables work best mostly empty - the same may be true with address blocks because they are allocated in routable units. But how does this really work?

The presumption of over 200 (254, or 252 for the annoyingly picky) Class A networks, each with about 16 million hosts (16*1024*1024-2 for the pointlessly obsessive) was the most hilarious, because nobody could explain how you could deal with a single network with 16 million hosts, much less some 200 of them. The claim was that a phone company using X.25 PADs might have 16 million subscribers connected in an odd configuration, but it was never to my knowledge deployed because of cost considerations. Actually, when it became possible with ISDN, it wasn't considered desireable by Pac Bell (Scott Adams was still in San Ramon then, BTW!) either as a business or technically (too much of a load for them to feel comfortable).

The counterpush at the time was for 64-bit object identifiers (for an unrelated project) - a ludicrously overblown number. For fun Ross Harvey calculated that 2^64 printed punchcards stacked one on the other would reach farther than the earth-sun distance. So one could go overboard in the opposite direction to little real purpose as well. I include this little item for those who like to test the waters by tossing in the baby.

So what this bulletin claims is that we are now out of sparse space and into dense space, i.e. if one did a fractal map of the 4 GByte address space it would have little unallocated. If true, this is an interesting juncture for ARIN and the IPv6 community. But is it true?

The concerns expressed over the exhaustion of IPv4 address space are similar to the concerns expressed over the exhaustion of telephone numbers. The assumption was that everyone had to have multiple cell phone numbers plus LAN lines plus separate computer lines and so forth, so the estimates ran from 4-10 lines per person. Area codes were split to accomodate new growth, and the press began to run stories about how we would run out of telephone numbers, contributing to a general hysteria. Companies began to over-order on blocks of phone numbers to "build-in" room for growth on their switches. In one Internet portal company where I managed their datacenter, I also had to budget this item, even though I noticed my staff was increasingly using mobile devices and advocated a single number to mobile redirect policy. This number peaked in the late 1990's and has since fallen as technologies were developed to combine voice / data, and LAN lines are wholesale abandoned for purely mobile devices.

Like the overbuying of phone lines of the 1990's, startups are often encouraged to budget for /19's even though the number of IP addresses actually used are very few, because the security demands of monitoring and securing open ports of such a large number of IPs overwhelm the IT staff, who in turn go to NAT (sometimes they really go overboard and reduce too much). As the IPv4 address space is used up and grows more expensive, perhaps there will be a similar collapse, where there are plenty of scattered small blocks which can be bartered among service providers. In this case, the ARIN announcement may simply be the peak before the drop.

So this is also an exciting opportunity for anyone who likes to make wagers. Is this the peak before the drop, like the phone number exhaustion hysteria of the 1990's, or is it something much deeper? Since even Dave notes that nobody has that many addresses in use already (sorry e2e - NAT is here to stay), yet ARIN is claiming otherwise, we may simply be seeing the end of an era of IP address block hoarding and not the beginning of a new address space boom.