|Issue:||Asia-Pacific III 2013|
|Topic:||Internet Addressing in the 2010s: IPv4 exhaustion and address transfers,|
and their impact on IPv6 deployment
|Organisation:||Asia-Pacific Network Information Centre (APNIC)|
Paul Wilson has twenty-five years’ involvement with the Internet, and nearly fifteen as the head of APNIC, and Regional Internet address Registry for the Asia Pacific. In his current role, he contributes expertise to many regional and global forums related to the development and governance of the Internet. In 2012 he was also selected to the Multi-stakeholder Advisory Group for the Internet Governance Forum (IGF).
Previously as CEO of Pegasus Networks, the first private ISP in Australia, Paul worked with the International Development Research Centre, helping to establish many early Internet services in developing economies of the region.
In 2000, Paul was inducted into the Australian Internet Hall of Fame.
The Internet has proved to be an incredible engine for economic growth, but it faces a global challenge with its depleting IPv4 addressing resources. Its future depends on a critical transition via parallel running of dual stack devices and though re-distribution of unused blocks of IPv4 addresses. What must be avoided is an emerging IPv4 addresses black market, which will add cost and will slow down IPv6 transition, and widespread adoption of carrier-grade NAT (CGN) for large ISP networks, which would erode the Internet’s neutrality and openness by linking to specific servers, raising the barrier for new entrants.
It is a well-known fact these days that the Internet, as a result of its unexpected success, is running out of the address space that is required for future growth. The current address space supply, which is provided by the “IPv4” standard, is close to exhaustion. As a result, future growth will require the deployment of “IPv6”, the next generation Internet Protocol.
IPv6 was standardized in 1999, and implementations have been available for many years, however its practical deployment and use on the Internet have been much slower than many expected. The reasons for this are mostly not technical, but related to economic and business factors in the provision of Internet services.
Specifically, it has often been observed that IPv6 deployment brings a vicious cycle of supply and demand dependency:
• IPv6 is designed to invisibly replace IPv4, making no immediate difference to Internet users; therefore there is no demand for IPv6 from ISP (Internet Service Providers) customers, nor an opportunity for ISPs to recover costs of the new service.
• Consequently ISPs and content providers have tended not to prioritise IPv6 service development, or to demand IPv6 support from their own suppliers.
• The once-hoped-for killer applications for IPv6 will not be developed until there is an infrastructure that they uniquely require, but neither can these imagined innovative services encourage IPv6 deployment until they actually exist.
Given this collusion of factors, it is not surprising that in reality, IPv6 deployment has not happened more quickly.
How long left for IPv4?
In the absence of demand for IPv6 as a new product or service, the critical driver towards its deployment can only be the lack of the IPv4 address space required for new Internet infrastructure. In this sense, the killer application for IPv6 is indeed the Internet itself, and not any specific feature that it can offer. In this case, surely, IPv6 should be an inevitable outcome of IPv4 address exhaustion, and one which will happen smoothly as required…?
This is only partially true. In theory, the vicious cycle described above should be broken when IPv4 addresses are finally exhausted and all participants are compelled to move to IPv6. In practice however the motivation of moving towards IPv6 will never be so evenly distributed or so predictable, because techniques are available to extend the lifetime of IPv4 in various ways.
Just as we see in the world of medicine, there are rarely any treatments without side-effects and without compromises between costs and benefits that they offer.
IPv4 Lives On: NAT
The first prescription for extending the life of IPv4 is Network Address Translation (NAT), which can greatly extend the practical use of a single public IP address by sharing it among many devices, in a similar way to how a telephone PBX works.
While PBXs bring few disadvantages to telephone users, large network NAT brings greater penalties, due to the need for fast response, reliability, automation and standardization of Internet transactions. This impact may be largely invisible in small-scale home or office NAT servers, because today’s Internet applications are built to operate through them; however it certainly increases where large scale CGN ( Carrier-Grade NAT) systems are used to carry services to thousands or millions of users. These CGN devices are still not widely available, but in widespread use they will certainly add huge additional complexity, inefficiency and cost to the Internet, as well as threatening network security and manageability.
Despite their costs and disadvantages, NAT/CGN systems are available as one option for ISPs to extend the lifetime of their IPv4 address holdings. Whether they do enter widespread usage will depend on the pace of future uptake of IPv6.
IPv4 Lives On: in an IP Address Market
Before the exhaustion of IPv4 address space, those who need public addresses are able to receive them readily from their appropriate Regional Internet Registry (RIR), at a reasonable cost, using well known procedures. “Black market” address transfer activity appears to have been very limited, and mostly confined to those who wished to conceal their address usage in any case (e.g. to conceal spamming activities).
As IPv4 exhaustion approached however, it becomes clear to many that an approved transfer mechanism could be useful in at least three ways:
1. to establish a means for those needing public IPv4 addresses to receive them;
2. to provide holders of unused or underutilized address blocks with an incentive to release them; and
3. to reduce the incentive for a black-market to emerge.
Currently, two RIRs – APNIC and ARIN (responsible for Asia Pacific and North America respectively) have active address transfer policies.
IPv4 Transfers and IPv6 Transition
It has been suggested that the availability of IPv4 transfers will further reduce the urgency of IPv6 deployment and delay the transition process. This is likely to be true, as the biggest driver for IPv6 deployment is the depletion of IPv4 address space.
That said, IPv6 transition requires concurrent action by as many parties as possible; and the current uneven distribution of IPv4 address space, particularly considering legacy IPv4 stocks in North America and Europe, defeats this requirement. Therefore while IPv4 transfers may indeed reduce the urgency for some parties, they will also serve to improve address distribution and with it, increased motivation for implementing IPv6 in the longer term, which is essential to a successful transition.
IPv4 Lives On: In a “Dual Stack” Internet
The transition to IPv6 is not a single event, either globally or in the case of individual service providers. The most favoured transition technique, known as “Dual-Stack” involves the parallel operation of both IPv4 and IPv6 in all components, applications and services on a given network, for an extended period of time. This should provide direct IPv4-IPv4 and IPv6-IPv6 connectivity wherever they are needed, without the use of inefficient unnecessary translations. However, for a long while, interaction between IPv4 and IPv6 devices and servers will still occur. By its nature, dual-stack involves the ongoing operation of IPv4, therefore it encourages IPv4 address space to be used where it is available, in dual-stacked infrastructure and devices. This is why, even under the best circumstances, the extended lifetime of IPv4, whether through NAT (private addressing) or transfer (public) mechanisms, is in fact a necessity for a smooth IPv6 transition.
With an effective and wide scale deployment of IPv6, the reliance on IPv4 in a dual stack environment will steadily diminish, since IPv6 is favoured wherever there is a choice. Across the Internet, IPv4 status would diminish from being the dominant majority protocol, to a secondary protocol to IPv6, to marginal one and then forgotten and entirely unused. The timescale of such a progression is probably in the order of five to ten years from start to finish, by most estimates, assuming that IPv6 transition does continue steadily and at a sufficient pace.
IPv6 and the Future Internet
It is widely recognized that IPv6 provides the only means of achieving long-term growth of the Internet while maintaining its critical technical features: its global nature, neutrality and openness. Even with the advent of IPv4 transfers, and the possible emergence of an IPv4 market, the future growth and success of the Internet is absolutely dependent on the successful deployment of IPv6.
The best prescription for IPv6 transition is a “Dual Stack” approach, using wherever possible, public IPv4 addresses available through a market-based transfer environment. Only this combination can provide an efficient growth path to a healthy IPv6-based Internet, and minimise wasted investments in NAT/CGN infrastructures which do not contribute to the IPv6 transition.
A failure of IPv6 deployment would not prevent global networks from continuing to grow, but would result in inevitable damage to or loss of critical technical features that today we take for granted. In particular, the widespread adoption of NAT, and CGN in particular, will steadily degrade the ability of Internet devices to connect to the Internet and to each other. In turn, the applications used by devices will rely increasingly on application-specific servers, which become less distinguished from the network infrastructure itself, compromising the neutrality of the Internet. Finally, the barriers to entry for new service providers, including ISPs, applications and content providers, will be raised by limited access to remaining supplies of public IPv4 address space, by the costs of distributing application servers within the infrastructure, and by the difficulty of distributing content outside of these established applications.
In such a future, the global network environment may still be referred to as “the Internet” but it would have lost the characteristics that have been critical to its success. This scenario is clearly not what we wish-for.