Every "host" (computer) on the Internet requires an IP number in order to interact over the network. The current number space is IP version 4 (IPv4) and it is running out of numbers. When there are no more numbers, no additional devices or subscribers can be added to the network.

In recognition of this limitation, in 1991, work was initiated on a next generation internet protocol. This work resulted in a new address space, IPv6. IPv6 dramatically increases the amount of IP address space available from the approximately 4.3 billion addresses in IPv4 to approximately 3.4 × 10³⁸. Because IPv6 uses a 128-bit address scheme rather than the 32-bit address scheme used in IPv4, it is able to allow many more possible addresses. The increase in the actual bits in the address and the immense number of possible combinations of numbers make the dramatic number of unique addresses a possibility. Figure 4 shows the difference between the length of an IPv4 address and that of an IPv6 address.

Differing analysts predict that the IPv4 space could be exhausted in the imminent future. [See IPv4 Depletion Projections] A few years ago, analysts concluded that while IPv4 exhaustion was a problem, the exhaustion horizon was decades away. The demands on the IPv4 space could be mitigated by number conversation efforts, NATs, and returning unused numbers to the numbering pool. New projections are concluding that IPv4 exhaustion is much more imminent[Bush slide 5] Pressures on the IPv4 space include the growth in the mobile Internet market, opening of new Internet markets in Asia, and new, number hungry, applications.

The key benefits of IPv6 include

• a dramatic increase in IP address space,
• a simplified IP header for flexibility and functionality,
• improved routing of data, [But see Bush Slide 12 (it is a myth that IPv6 reduces routing load)]
• enhanced mobility features,
• easier configuration capabilities,
• improved quality of service, and
• integrated Internet protocol security. [But see Bush Slide 12 (it is a myth that IPv6 has better security)]

Some things that IPv6 does not do include eliminate NATs. [Bush Slide 11] NATs may serve as part of a transition solution. IPv6 also does not eliminate the need for CIDR. [COOK]

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.

This large number of IPv6 addresses means that almost any electronic device can have its own address. While IP addresses are commonly associated with computers, they are increasingly being assigned to communications devices such as phones and other items such as consumer electronics and automobiles.

IPv6 addresses are characterized by a network prefix that describes the location of an IPv6-capable device in a network and an interface ID that provides a unique identification number (ID) for the device. The network prefix will change based on the user’s location in a network, while the interface ID can remain static. The static interface ID allows a device with a unique address to maintain a consistent identity despite its location in a network. In IPv4, the limited address space has resulted in a plethora of network address translation devices, which severely limits the possibilities for end-to-end communications. In contrast, the massive address space available in IPv6 will allow virtually any device to be assigned a globally reachable address. This change fosters greater end-to-end communication
abilities between devices with unique IP addresses and can better support the delivery of data-rich content such as voice and video.

Simplifying the IPv6 header promotes flexibility and functionality for two reasons. First, the header size is fixed in IPv6. In the previous version, header sizes could vary, which could slow routing of information. Second, the structure of the header itself has been simplified. While the IPv6 addresses are significantly larger than in IPv4, the header containing the address and other information about the data being transmitted has been simplified. The 14 header fields from IPv4 have been simplified to 8 fields in IPv6. Figure 5 illustrates the differences between the two IP headers, including the various data fields that were eliminated, renamed, or reorganized.

Another benefit of the simplified header is its ability to accommodate new features, or extensions. For example, the next header field provides instructions to the routers transmitting the data across the Internet about how to manage the information.

The improved routing, or movement of information from a source to a destination, is more efficient in IPv6 because it incorporates a hierarchal addressing structure and has a simplified header. The large amount of address space allows organizations with large numbers of employees to obtain blocks of contiguous address space. Contiguous address space allows organizations to aggregate addresses under one prefix for identification on the Internet. This structured approach to addressing reduces the amount of information Internet routers must maintain and store and promotes faster routing of data. In addition, as shown in figure 5, IPv6 has a simplified header because of the elimination of six fields from the IPv4 header. The simplified header also contributes to faster routing.

Note: Scalable routing is listed as a concern with IPv6; that IPv6 with its massive increase in IP addresses will create increased demands on routing and routers - to the point where the increased demands become problematic.

IPv6 improves mobility features by allowing each device (wired or wireless) to have a unique IP address independent of its current point of attachment to the Internet. As previously discussed, the IPv6 address allows computers and other devices to have a static interface ID. The interface ID does not change as the device transitions among various networks. This enables mobile IPv6 users to move from network to network while keeping the same unique IP address. The ability to maintain a constant IP address while switching networks is cited as a key factor for the success of a number of evolving capabilities, such as evolving telephone technologies, personal digital assistants, laptop computers, and automobiles.

IPv6 enhancements can ease difficult and time-consuming aspects of network administration tasks in today’s IPv4 networks. For example, two new configuration enhancements of IPv6 include automatic address configuration and neighbor discovery. These enhancements may reduce network administration burdens by providing the ability to more easily deploy and manage networks.

IPv6 supports two types of automatic configuration: stateful and stateless. Stateful configuration uses the dynamic host configuration protocol. This stateful configuration requires another computer, such as a server, to reconfigure or assign numbers to network devices for routing of information, which is similar to how IPv4 handles renumbering. Stateless automatic configuration is a new feature in IPv6 and does not require a separate dynamic host configuration protocol server as in IPv4.

Stateless configuration occurs automatically for routers and hosts. Another configuration feature—neighbor discovery—enables hosts and routers to determine the address of a neighbor or an adjacent computer or router.

Together, automatic configuration and neighbor discovery help support a plug-and-play Internet deployment for many devices, such as cell phones, wireless devices, and home appliances. These enhancements help reduce the administrative burdens of network administrators by allowing the IPv6- enabled devices to automatically assign themselves IP addresses and find compatible devices with which to communicate.

IPv6’s enhanced quality of service feature can help prioritize the delivery of information. The flow label is a new field in the IPv6 header. This field can contain a label identifying or prioritizing a certain packet flow, such as a video stream or a videoconference, and allows devices on the same path to read the flow label and take appropriate action based on the label. For example, IP audio and video services can be enhanced by the data in the flow label because it ensures that all packets are sent to the appropriate destination without significant delay or disruption.

IP Security—a means of authenticating the sender and encrypting the transmitted data—is better integrated into IPv6 than it was in IPv4. This improved integration, which helps make IP Security easier to use, can help support broader data protection efforts. [But see Bush Slide 12 (it is a myth that IPv6 has better security)] [Underwood ("IPSEC, invented for IPv6 is in every IPv4 implementation")]

IP Security consists of two header extensions that can be used together or separately to improve authentication and confidentiality of data being sent via the Internet. The authentication extension header provides the receiver with greater assurance of who sent the data. The encapsulating security header provides confidentiality to messages using encrypted security payload extension headers.

IPv6’s increased address space, functionality, flexibility, and security help to support more advanced communications and software applications than are thought to be possible with the current version of IP. For example, the ability to assign an IP address to a wide range of devices beyond computers creates many new possibilities for direct communication. While applications that fully exploit IPv6 are still in development, industry experts have identified various federal functions that might benefit from IPv6-enabled applications:

• Border security: could deploy wireless sensors with IPv6 to help provide situational awareness about movements on the nation’s borders.
• First responders: could exploit the hierarchal addressing of IPv6 to promote interoperability and rapid network configuration in responding to emergencies.
• Public health and safety: could exploit IPv6 end-to-end communications to deliver secure telemedicine applications and interactive diagnoses.
• Information sharing: could benefit from various features of IPv6, including securing data in end-to-end communications, quality of service, and the extensibility of the header to accommodate new functions.

Barriers to Transition:

Cost. The transition from IPv4 to IPv6 is compared to the cost of the Y2K work. It is a substantial investment which profit sensitive companies are inclined to put off. [AT&T: New Gen of the IP]

Trained Staff: Hiring staff trained and experienced with IPv6.

Incentives: As long as there are some IPv4 numbers available, the incentive to migrate to IPv6 is limited.

Network Effect: IPv6 networks can only reach IPv6 assets (absent some transition kludge). Therefore, if there are few resources available on the Net that can be reached by an IPv6 network, there is little incentive to transition. At some point this will tip, where there are sufficient resources on IPv6 networks and the network effect is sufficiently valuable to create an incentive to transition.

[ICANN 10-07]

Failure to transition to IPv6: Networks that fail to transition to IPv6 and who are unable to procure addition IPv4 resources will be unable to acquire new customers and will be unable to add new devices to their networks. [Cook] Cook also discusses increased pressure on the routing table, to the critical point where networks will begin to shed routes and the Internet will fracture - not all points will be reachable from any one given point on the net.

As IPv4 numbers become more scarce, there are predictions that secondary markets and speculation will emerge. [ICANN 10-2007] This may drive the price of IPv4 numbers up. However, as the price of IPv4 numbers goes up, networks that need numbers will have a greater economic incentive to transition to IPv6. The OECD is reportedly researching the economic impact of a potential IPv4 number shortage.

See IPv6 Transition.