This expansion is necessary because the current number of addresses under Internet Protocol version four (IPv4) is gradually being exhausted.

WHITEHOUSE: Office of Science and Technology Policy Blog

In a world where a growing number of devices have Internet protocol addresses, building security into these systems has never been more important.

FORBES: The Biggest Cybersecurity Threats of 2013

Internet Protocol version six, or IPv6, is an Internet addressing system designed to expand the number of available IP addresses.

WHITEHOUSE: Office of Science and Technology Policy Blog