Summary of the Analysis
Based on number 17% available number, and 3.7 billion total IP address space number, available IP addresses in Oct ‘07 are 629M.
There are a variety of predictions, using different models, that attempt to estimate when there will be no more IPv4 addresses to allocate. The cut-off date ranges from 2009 to 2013.
It is now the widespread opinion of the technical community that for the continued and uninterrupted expansion of the Internet, it is vital that IPv6 adoption begin in earnest.
Various Papers Analyzing IPv4 Exhaustion Date
Here are some of the selected papers from around the web analyzing IPv4 exhaustion date.
- Very Detailed Information about IPv4 addresses where they are and how are they consumed.
- ICANN’s IPv6 Factsheet: Published in Oct ‘07 said that 17% of IPv4 addresses are available
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- Ars Technica article predicsts that at current rate we have 7.5 years before running out of IPv4 addresses. However, givent publication from ICANN the number of left IP addresses here cannot be accurate.
Available IPv4 Addresses as of Oct '07 (From ICANN paper: Blue is Available)
What About NAT?
NAT was discovered in ’90s. NAT has served us well. Nearly all the enterises and most homes using more the one host is using NAT. The NAT in effect allows us to create several private Internets each using the same set of IP addresses. The IETF has reserved IP address space for private Internets. The hosts within the same private Internet can communicate with each other using private IP addresses. A device behind NAT only needs to use a public IP address when the host communicates with the public IP Internet. This allowed sharing of a single public IP addresses for several hosts.
Can NATs be promoted to the operators networks? If we can, we can delay the date of IP address exhausion by several years if not for ever. The NAT works well for outgoing only connections like web access, POP/SMTP based e-mail access. However, they have serious problems for incoming connections like VoIP, P2P, some game plays etc. At home the solution for incoming connection typically involves port forwarding which can be manually configured or auto-configured using UPnP.
In the current Internet, our ISPs provide us pipe and do not control what type of applications we run on our computers and how they use the pipe. Installation of NAT in the operator’s network will change this model since they will only be able to provide outgoing only connections.
It is possible for the operators to provide two types of services. Outgoing only service which is mostly used for browsing and e-mail and the second class providing access to all the services. The operator could deploy NAT for the first set of subscriber and provide public IP addresses to the second class of subscribers and have differential charging.
If this had to happen lots of newer mobile devices could use browse only IP addresses and can be sufficiently served by NAT. The operators can deploy application level proxies to deal with specific protocol needs like IMS. This will limit innovation in the Internet since several applications will not be able to run on these devices.
The impact of this design on overall IP address consumption is not clear but it should delay need to deploy IPv6 significantly.
If this has to happen, this will fundamentaly change the nature of the Internet. At present North American operators are very reluctant to deploy NAT in their networks.
Effect of IPv4 Exhaustion
Blogs have tried to compare IPv4 exhaustion to Y2K. However, the impact of IPv4 exhaustion will be a lot less dramatic. If the Internet is not ready with IPv6, several possible things can happen:
- Operators can deploy limited NAT for certain class of subscribers, devices extending life of IPv4 addresses they already have
- There is significant IPv4 address space which is allocated to different organizations. It is possible that this IP addresses can be sold back to the ISPs at a cost or can be reallocated by ICANN extending life of IPv4 address space.
- Operators can deploy limited IPv6 on devices with limited applications (e.g. Comcast recently announced that they will move management of home modems to IPv6)
- Operators will move quickly towards IPv6.
It is clear as we move closer to IPv4 address exhaustion, the cost of IPv4 will increase. The ISPs at that time will have a choice whether to move to IPv6 or live with restrictions, cost imposed by IPv4.
