Final answer:
The Internet's supply of IPv4 addresses ran out in 2011 due to the limited number of available addresses in its 32-bit system. This led to the development of IPv6, which has a much larger address space with its 128-bit system.
Step-by-step explanation:
The Internet's supply of IPv4 addresses ran out in 2011. The IPv4 (Internet Protocol version 4) is an addressing system that was developed for the internet in the early 1980s and uses a 32-bit address scheme which allows for a maximum of about 4.3 billion unique addresses. Due to the explosive growth of the internet and the number of devices connected, the available IPv4 addresses became inadequate to accommodate all the devices. This limitation led to the development and gradual adoption of IPv6 (Internet Protocol version 6), which utilizes a 128-bit address system, vastly increasing the number of possible addresses.