The Advantages of IPv6

The massive growth of the Internet has demonstrated its value to businesses, government, professionals, academics and individuals over the last decade. Industry now relies on on a range of benefits from Internet technology and has seen significant productivity gains.

The benefits of the Internet are drawn directly from the platform of interoperability created by use of the Internet Protocol, leading to a large "network effect". That is, the benefits to a company from the Internet arise not just by the extent to which the company itself uses the Internet, but far more from the extent to which others - suppliers, customers and individuals - also use the Internet. Because IPv6 will greatly increase the size and range of devices connected to the Internet, the benefit of the network effect will increase accordingly.

The World Wide Web and other Internet applications currently use version 4 of the Internet Protocol - IPv4. IP version 6 was developed by the Internet Engineering Task Force to deal with a looming shortage of addresses under IPv4. Since then, there have been numerous technical fixes to shore up IPv4 and postpone the need for a move to IPv6, as well as debate on whether IPv6 would even be required. That debate is now generally agreed to be over. The IPv4 address space is expected to run out around 2011 if there is no change to the existing rates of allocation. In practice, the only option for those building large new networks is to use IPv6.

Complexity has been introduced into the way that IP based-networks are already implemented because of address space shortage. Parts of the IPv4 address space need to be reused around the world because there are now too few addresses remaining for the size of the Internet. Some IPv4 address space has been reserved for private (not globally routable) IPv4 addresses, to help overcome these problems. These allocations have been used with network address translation to enable networks to connect to the Internet using only one globally routable IPv4 address. For example, in India, up to three levels of Network Address Translation have been observed.

IPv6 offers the potential to build a much more powerful Internet, with vastly larger scale compared to the current situation. Addresses in IPv4 have only 32 bits, allowing for only about 4 billion addresses, compared to 128-bit IPv6, with some 340 trillion, trillion, trillion addresses.

As well as increasing the address space, the IETF took the opportunity to build additional features into the IPv6 specification. IPv6 has a new feature called autoconfiguration. This feature allows a device to generate an IPv6 address as soon as it is given power. Using this 'link local' address, there is no immediate need for any other infrastructure to allow that device to begin communicating via IPv6 on its local network, including communications with another local host or router. If an IPv6 router is present, any IPv6-capable device can generate not only a local address, but a globally routable address, allowing access to the wider Internet.

Provision of sufficient address space will also allow re-establishment of an end-to-end architecture in the Internet. The shortage of IPv4 addresses has caused widespread use of private address spaces, which are not directly accessible from the Internet. Devices with IPv6 addresses and IPv6 connectivity can be directly reachable by their address. Such an approach gives rise to the potential to move beyond an "Internet of desktops" to an "Internet of devices" where device to device communication becomes possible. A range of other capabilities were included during the IPv6 development process, for instance mandatory support for security via IPsec (Internet Protocol Security).

While some of the new features possible in IPv6 based networks are currently possible in IPv4 based networks, the critical exception is that they do not support the scale that IPv6 does, making it difficult or impossible to use them to meet current and future business requirements. The network applications being considered as a basis for new growth in industry productivity require a vastly higher scale of implementation than IPv4 can deliver; thousands or millions of devices and/or addresses.

Comcast (a large cable operator based in the USA) moved to IPv6 because it was in need of over 100 million addresses. Simple projections showed Comcast that the number of IP addresses that Comcast would need in order to support its future growth in terms of subscriber base, as well as to be able to leverage potential new services, exceeded those available. In fact, estimations were that within a few years, Comcast would have some 20 million video customers, an average of 2.5 set-top boxes per customer, and 2 IP addresses per box. If these estimates are correct, the company will be needing over 100 million IP addresses.

Manual intervention is the other critical element to be considered in the context of implementing large scale networks. If manual set-up is required for every device with an IP address, significant costs will be incurred. In IPv4 based networks, this requirement has been alleviated by the use of server based configuration of devices using Dynamic Host Configuration Protocol (DHCP) which is able to automatically allocate IP addresses to new devices on the network with the parameters set by the network administrator. However, for this approach to work, each new device must interact with a DHCP server, which in the case of large-scale networks is resource- and time-intensive. In contrast, IPv6 address allocation is done by the device itself and can occur independently of a server, or in conjunction with an IPv6 enabled router, as appropriate.

While many Internet based applications will continue to operate under IPv4, the challenges of network administration and security management continue to grow. For instance, if two companies merge and want to merge their IP based networks then there will have to be renumbering. On the Internet, if the source of malevolent activity needs to be identified, the closest identification by IP address possible under an IPv4 NAT architecture is the globally routable IPv4 address of the top level NAT server.

In the case of much larger scale future networks (such as in the Comcast example above), industry will face significant challenges. In an Australian example, Telstra is rumoured to be using Class A private address space to address NextG devices, which would limit their capacity to grow a market beyond Australia. In summary, IPv6 has significant cost advantages in current networks, and in developing the larger scale networks required by industry.