Random wonderings: IPv4 and NANP exhaustion

So this morning I was rudely awakened at about 3:30am, and my tired mind wandered and came up with a question I had to find an answer to.

Without going into a lot of technical background, IPv4 was invented in 1980. roughly 31 years later (2001) it’s 2^32 addresses (4,294,967,296 — some of which are reserved) were completely allocated and exhausted. The foreseeable exhaustion of these addresses led to the development of IPv6, which supports 2^64 addresses.

This got me thinking about the North American Numbering Plan (NANP) for telephone numbers, which had an address space of roughly 10^10 phone numbers (10,000,000,000 — some of which are reserved) which has been operating since 1947 (66 years!).

When would this number space be exhausted, and how would that event be handled?

Well, it turned out this is something carefully monitored by NANPA, the North American Numbering Plan Administration. They do not expect the current NANP number pool to exhaust until after 2042 (another 29 years, for a running total of 95 years in it’s current format!). While the potential changes haven’t been formalized yet, it appears that the most likely method will involve migrating to 4-digit area codes, as well as possibly inserting a prefix digit between the area code and prefix, for a total of 11 or 12 dialing digits (not including the country code).

So there you go.

Further reading:

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