As of January 2011 experts are warning that IPv4 Internet addresses will be used up around the world. IPv4 is the fourth revision in the development of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. IPv4 uses 32-bit (four-byte) addresses, which limits the address space to 4,294,967,296 possible unique addresses. Its successor IPv6, uses a 128-bit address and supports 2 to the 128th power addresses.
IPv6 deployment is still in its infancy but will see further adoption quickly over 2011. Some sites have already taken advantage of using IPv6 addressing. Read more about the IPv6 protocol here.
Internet addresses are distributed by the Internet Corporation for Assigned Names and Numbers, which provides them to five regional organizations around the world.