ICANN plays a similar administrative role with the IP addresses used by computers as it does with the domain names used by humans. In the same way that you cannot have two domain names the same (otherwise you never know where you would end up), for the same reason it is also not possible for there to be two IP addresses the same.
Again, ICANN does not run the system, but it does help co-ordinate how IP addresses are supplied to avoid repetition or clashes. ICANN is also the central repository for IP addresses, from which ranges are supplied to regional registries who in turn distribute them to network providers.
Internet Protocol (IP) addresses are the unique numeric identifiers assigned to everything that is connected to the Internet, from web servers, through smartphones to cameras and printers. The most widely-used version of the Internet Protocol, IPv4, was developed in the early 1980s and has served the global Internet community for more than three decades. IPv4 has a capacity of just over 4 billion IP addresses, which seemed like more than enough for the experiment that the Internet started as in the 1080s. But after years of rapid Internet expansion, the pool of available unallocated IPv4 addresses has been almost fully allocated to Internet services providers (ISPs) and users.
IPv4 is the version 4 of the Internet Protocol. It refers to the version of the Internet protocol that can operate with 32-bit IP addresses. This allows about four billion unique IP addresses, which is not enough to meet the demand projected for the next five to ten years. Therefore, a new protocol, called IPv6, was developed to significantly increase the number of available IP addresses.
On May 20, 2014, ICANN announced that it has begun the process of allocating the remaining blocks of Internet Protocol version 4 (IPv4) addresses to the five Regional Internet Registries (RIR). The activation of this procedure was triggered when Latin America and Caribbean Network Information Centre's (LACNIC) supply of addresses dropped to below 8 million.
This move signals that the global supply of IPv4 addresses is reaching a critical level. As more and more devices come online, the demand for IP addresses rises, and IPv4 is incapable of supplying enough addresses to facilitate this expansion. ICANN encourages network operators around the globe to adopt IPv6, which allows for the rapid growth of the Internet.
To handle this critical drop in the numbers available to LACNIC, the five RIRs' policy making communities established a policy for the equal redistribution by ICANN. This is known as the allocation phase outlined in the Global Policy for Post Exhaustion IPv4 Allocation Mechanisms.
IPv6 facilitates the exponential growth of the Internet by providing 340-undecillion unique addresses, compared to the 3.7 billion afforded by IPv4.