The Internet is a worldwide network of networks comprised of servers, routers, and backbone networks. Network addresses are used to help send information from one computer to another over the Internet by routing the information to its final destination. The protocol that enables the administration of these addresses is the Internet protocol (IP). The most widely deployed version of IP is version 4 (IPv4). The two basic functions of IP include (1) addressing and (2) fragmentation of data, so that information can move across networks. An IP address consists of a fixed sequence of numbers. IPv4 uses a 32-bit address format, which provides approximately 4.3 billion unique IP addresses. Figure 1 provides a conceptual illustration of an IPv4 address. By providing a numerical description of the location of networked computers, addresses distinguish one computer from another on the Internet. In some ways, an IP address is like a physical street address. For example, in the physical world, if a letter is going to be sent from one location to another, the contents of the letter must be placed in an envelope that contains addresses for the sender and receiver. Similarly, if data is going to be transmitted across the Internet from a source to a destination, IP addresses must be placed in an IP header. Figure 2 provides a simplified illustration of this concept. In addition to containing the addresses of sender and receiver, the header also contains a series of fields that provide information about what is being transmitted. The fields in the header are important to the protocol’s second main function: fragmentation of data. IP fragments information by breaking it into manageable parts. Each part has its own header that contains the sender’s address, destination address, and other information that guides it through the Internet to its intended destination. When the various packets arrive at the final destination, they are put back together into their original form. Several key organizations play a role in coordinating protocol development and Internet management issues, including the following: The Internet Corporation for Assigned Names and Numbers, (ICANN), is a nonprofit corporation responsible for Internet address space allocation and management of the Internet domain name system. Regional Internet Registries allocate Internet address blocks from ICANN in various parts of the world and engage in joint projects, liaison activities, and policy coordination. The registries include the African Network Information Center, Asia Pacific Network Information Centre, American Registry for Internet Numbers, Latin American and Caribbean Internet Addresses Registry, and Réseaux IP Européens Network Coordination Centre. Competing companies known as registrars are able to assign domain names, the mnemonic devices used to represent the numerical IP addresses on the Internet (for example, www.google.com). More than 300 registrars have been accredited by ICANN and are authorized to register domain names ending in .biz, .com, .coop, .info, .name, .net, .org, or .pro. A complete listing is maintained on the InterNIC Web site. The Internet Society is a large, international, professional organization that provides leadership in addressing issues that may affect the future of the Internet and assists the groups responsible for Internet infrastructure standards. The Internet Society also provides legal, financial, and administrative support to the Internet Engineering Task Force (IETF). IETF is the principal body engaged in the development of Internet standards. It is composed of working groups that are organized by topic into several areas (e.g., routing, transport, security, etc.). Limited IPv4 address space prompted organizations that need large amounts of IP addresses to implement technical solutions to compensate. For example, network administrators began to use one unique IP address to represent a large number of users. By employing network address translation, an enterprise such as a federal agency or a company could have large numbers of internal IP addresses, but still use a single unique address that can be reached from the Internet. In other words, all computers behind the network address translation router appear to have the same address to the outside world. Figure 3 depicts this type of network configuration. While network address translation has enabled organizations to compensate for the limited number of globally unique IP addresses available with IPv4, the resulting network structure has eliminated the original end-to-end communications model of the Internet. Network address translation complicates the delivery of real-time communications over the Internet. In 1994, IETF began reviewing proposals for a successor to IPv4 that would increase IP address space and simplify routing. IETF established a working group to be specifically responsible for developing the specifications for and standardization of IPv6. Over the past 10 years, IPv6 has evolved into a mature standard. A complete list of IPv6 documents can be found at the IETF Web site. Interest in IPv6 is gaining momentum around the world, particularly in parts of the world that have limited IPv4 address space to meet their industry and consumer communications needs. Regions that have limited IPv4 address space such as Asia and Europe have undertaken efforts to develop, test, and implement IPv6. As a region, Asia controls only about 9 percent of the allocated IPv4 addresses, and yet has more than half of the world’s population. As a result, the region is investing in IPv6 development, testing, and implementation. For example, the Japanese government’s e-Japan Priority Policy Program mandated the incorporation of IPv6 and set a deadline of 2005 to upgrade existing systems in both the public and private sector. The government has helped to support the establishment of the IPv6 Promotion Council to facilitate issues related to development and deployment and to provide tax incentives to promote deployment. In addition, major Japanese corporations in the communications and consumer electronics sectors are also developing IPv6 networks and products. The Chinese government’s interest in IPv6 resulted in an effort by the China Education and Research Network Information Center to establish an IPv6 network linking 25 universities in 20 cities across China. In addition, China has reportedly set aside approximately $170 million to develop an IPv6- capable infrastructure. Taiwan has also started to work on developing IPv6 products and services. For example, the Taiwanese government announced that it would begin developing an IPv6-capable national information infrastructure project. The planned initiative is intended to deploy an infrastructure capable of supporting 6 million users by 2007. In September 2000, public and private entities in India established the Indian IPv6 Forum to help coordinate the country’s efforts to develop and implement IPv6 capabilities and services. The forum hosted an IPv6 summit in 2005. The European Commission initiated a task force in April 2001 to design an IPv6 Roadmap. The Roadmap serves as an update and plan of action for the development and future perspectives of IPv6. It also serves as a way to coordinate European efforts for developing, testing, and deploying IPv6. Europe currently has a task force that has the dual mandate of initiating country/regional IPv6 task forces across European states and seeking global cooperation around the world. Europe’s task force and the Japanese IPv6 Promotion Council forged an alliance to foster worldwide deployment. Latin America also has begun developing projects involving IPv6. Some of these projects include an IPv6 interconnection among all the 6Bone sites of Latin America and a Native IPv6 Network via Internet2. Also in Mexico, the National Autonomous University of Mexico has been conducting research. In 1999, the university acquired a block of address space to provide IPv6-enabled service to Mexico and Latin America. Established in 2001, the North American IPv6 Task Force promotes the use of IPv6 within industry and government and provides technical and business expertise for the deployment of IPv6 networks. The task force is composed of individual members from the United States and Canada who develop white papers and deployment guides, sponsor test and interoperability events, and collaborate with other task forces from around the world. Currently, the task force, the University of New Hampshire, and DOD are collaborating on a national IPv6 demonstration/test network. In 2003, the President’s National Strategy to Secure Cyberspace identified the development of secure and robust Internet mechanisms as important goals because of the nation’s growing dependence on cyberspace. The strategy stated that the United States must understand the merits of, and the obstacles to, moving to IPv6 and, based on that understanding, identify a process for moving to an IPv6-based infrastructure. To better understand these challenges, the Department of Commerce formed a task force to examine the deployment of IPv6 in the United States. As co-chairs of that task force, the Commerce Department’s National Institute of Standards and Technology (NIST) and the National Telecommunications and Information Administration invited interested parties to comment on a variety of IPv6-related issues, including: (1) the benefits and possible uses; (2) current domestic and international conditions regarding the deployment; (3) economic, technical, and other barriers to the deployment; and (4) the appropriate role for the U.S. government in the deployment. As part of the task force’s work, the Department of Commerce issued a draft report in July 2004, Technical and Economic Assessment of Internet Protocol Version 6, that was based on the response to their request for comment. Many organizations and individuals—such as private sector software, hardware, and communications firms, and technical experts—responded, providing their views on the benefits and challenges of adopting the new protocol. The key characteristics of IPv6 include a dramatic increase in IP address space, a simplified IP header for flexibility and functionality, improved routing of data, improved quality of service, and integrated Internet protocol security. These key characteristics of IPv6 offer various enhancements relative to IPv4 and are expected to increase Internet services and enable advanced Internet communications that could foster new software applications for federal agencies.