The Internet Protocol (IP) is an international communications standard that is essential to the operation of both the public Internet and many private networks in existence today. IP provides a standardised 'envelope' that carries addressing, routing, and message-handling information, thereby enabling a message to be transmitted from its source to its final destination over the various interconnected networks that comprise the Internet. The current generation of IP, version 4 (IPv4), has been in use for more than 20 years and has supported the Internets rapid growth during that time. With the transformation of the Internet in the 1990s from a research network to a commercialised network, concerns were raised about the ability of IPv4 to accommodate anticipated increasing demand for Internet addresses. In 1993, the Internet Engineering Task Force (IETF) began a design and standardisation process to develop a next generation Internet Protocol that would address, among other issues, the predicted exhaustion of available IPv4 addresses. The resulting set of standards, collectively known as IP version 6 (IPv6), was developed over the course of several years. Although various aspects of these protocols continue to evolve within the IETF, a stable core of IPv6 protocols emerged by 1998. This book examines the technical and economic issues related to IPv6 adoption in the United States, including the appropriate role of government, international interoperability, security in transition, and costs and benefits of IPv6 deployment.