And so it begins… today it was announced that the final two unallocated “/8″ address blocks from IANA’s IPv4 address pool were allocated to APNIC, the Asia-Pacific Regional Internet Registry. With this action, there are only five remaining unallocated /8 blocks, and per ICANN’s global policy IANA will now allocate these remaining 5 blocks to each of the 5 RIRs.
This is the beginning of the end of IPv4 address availability.
But to understand what this means, let’s put a bit of context around it.
What is a “/8″ address block?
In practical terms, a “/8 block” is a block of IPv4 addresses that all have the same first number in the IP address. In the case of APNIC’s allocation today, they have two blocks that were allocated to them:
39.x.x.x
160.x.x.x
They can now turn around and allocate out to Internet Service Providers (ISPs) subsets of those address blocks. So one ISP might get the 254 addresses in “39.1.5.x” and another ISP would get the 254 addresses in “39.1.6.x” … and so on.
Each “/8″ block allows for 16,777,214 IPv4 addresses (2^24 – 2), although with routing requirements not all those addresses can be used.
(And yes, the technical answer is that with a “/8″, the first 8 bits of the address (the first number in the “octet”) represent the “network” and the remaining 24 bits represent the “host”. In the old days, we used to call these “Class A” addresses, and companies used to easily get one.)
Does this means the Internet stops tomorrow?
No. Media hype excluded, the Internet will keep on working perfectly fine, just as it normally does.
So what will happen? What does this mean?
17 million addresses (in a /8) is a good number… but consider how many new mobile devices we are adding to the global Internet each and every day. Consider how many sensors we are adding to the global Internet every day… IP webcams, temperature sensors, remote devices. Consider how many new computers are being purchased each day and added to the Internet.
Everyone wants connectivity. For connectivity you need an IP address of some type.
The RIR’s allocate IPv4 addresses to ISP’s, who in turn allocate IPv4 addresses out to individual customers (or the may allocate IPv4 addresses to smaller ISPs, who in turn allocate addresses to customers).
Using techniques like Network Address Translation (NAT), a customer can put a large number of devices behind a single IPv4 address (using the “private” IPv4 address blocks of 10.x.x.x, 192.168.x.x and a subset of the 172.x.x.x. address space defined in RFC 1918). So a mobile provider could, for instance, put millions of handsets behind a single public IPv4 address.
The challenge is that:
- the IPv4 pool of publicly routable addresses will still eventually run out; and
- some applications don’t work well with NAT in the way.
What this all means is that sooner or later…
the RIRs will no longer be able to give IPv4 addresses to their ISPs… and the ISPs will no longer be able to give out IPv4 addresses to customers.
So if you want to bring new customers online through that nifty gadget you created, or the new smartphone you want to market, there may be a challenge getting actual addresses for those devices.
In the note from APNIC, they state:
APNIC expects normal allocations to continue for a further three to six months.
And then they will dramatically tighten up the requirements for getting an IPv4 address. As APNIC notes, there may still be IPv4 addresses available for as long as five years, but it will become increasingly hard to justify obtaining one. And then at some point they will simply be gone.
So where do we go from here?
As the pool of IPv4 addresses nears exhaustion, I think we can expect to see many service providers look at implementing very large-scale NAT to continue to use IPv4 as long as humanly possible. This will “work” to a degree, but it will create a mess of a network and may certainly lead to challenges with applications and services being able to reach all the endpoints out there.[1]
The real answer lies in moving to IPv6, the new addressing scheme that provides an enormously larger IP address space. (And about which I’ve been writing about here.) The challenge is that companies and ISPs need to invest in the equipment for an IPv6 infrastructure[2] and they need to check that their applications work with IPv6, etc., etc. It’s not a simple process.
But here we are… the last allocations of IP4 addresses are beginning… the long slow final dance of IPv4 has begun…
[1] The good news for network equipment vendors is that they will be able to sell a ton of proxy servers, SBCs and other NAT traversal devices and software.[3]
[2] The good news for network equipment vendors is that they will be able to sell a ton of IPv6-compliant devices and software.[3]
[3] The lesson here is that it is a very good time to be a network equipment provider!
What about IPv6-capable devices in the home? FierceTelecom has a great post out reminding us all that it’s not enough to ensure that the back-end infrastructure is IPv6-capable – 
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