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IPv4 address exhaustion

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IPv4 address exhaustion is the decreasing supply of unallocated IPv4 addresses available at the Internet Assigned Numbers Authority (IANA) and the regional Internet registries for assignment to end users and local Internet registries, such as Internet service providers. IPv4 only provided for approximately 4 billion addresses with a current primary allocation granularity of /8 blocks by IANA, a limit that is estimated to be reached before 2012.

The depletion of the IPv4 allocation pool has been a concern since the late 1980s when the Internet started to experience dramatic growth. The Internet Engineering Task Force (IETF) created the Routing and Addressing group (ROAD) in November 1991 to respond quickly to the scalability problem caused by the classful network allocation system in place at the time.[1][2]

The anticipated shortage has been the driving factor in creating and adopting several new technologies, including classful networks in the 1980s[citation needed], Classless Inter-Domain Routing (CIDR) methods in 1993, network address translation (NAT) and a new version of the Internet Protocol, IPv6, in 1998.[2]

The transition of the Internet to IPv6 is the only practical and readily available long-term solution to IPv4 address exhaustion. Although the predicted IPv4 address exhaustion approaches its final stages, most ISPs, software vendors and service providers were just beginning IPv6 deployment in 2008.[3]

IP addressing

Every host on an IP network, such as a computer or networked printer, is assigned an IP address that is used to communicate with other hosts on the same network or globally. Internet Protocol version 4 provides 232 (approximately 4.3 billion) addresses. However, large blocks of IPv4 addresses are reserved for special uses and are unavailable for public allocation.

The IPv4 addressing structure provides an insufficient number of publicly routable addresses to provide a distinct address to every Internet device or service. This problem has been mitigated for some time by changes in the address allocation and routing infrastructure of the Internet. Classful networking and particularly Classless Inter-Domain Routing delayed the exhaustion of addresses substantially.

In addition, the technique of network address translation (NAT) permitted large ISPs to allocate only one public IP address to each of their customers, by masquerading the customer network behind this address with specially configured customer-premise Internet routers.

Address depletion

While the primary reason for IPv4 address exhaustion is insufficient design capacity of the original Internet infrastructure, several additional driving factors have aggravated the shortcomings. Each of them increased the demand on the limited supply of addresses, often in ways unanticipated by the original designers of the network.

Mobile devices
As IPv4 increasingly became the de facto standard for networked digital communication, the cost of embedding substantial computing power into handheld devices dropped. Mobile phones have become viable Internet hosts. New specifications of 4G devices require IPv6 addressing.
Always-on connections
Throughout the 1990s, the predominant mode of consumer Internet access was telephone modem dialup. The rapid growth of the dialup networks increased address consumption rates, although it was common that the modem pools, and as a result, the pool of assigned IP addresses, were shared to a large degree amongst a larger customer base. By 2007, however, broadband Internet access had begun to exceed 50% penetration in many markets.[4] Broadband connections are usually always active, as the gateway devices (routers, broadband modems) are rarely turned off and require minimal power, so that the address uptake by Internet service providers continued at an accelerating pace.
Internet demographics
There are hundreds of millions of households in the developed world. In 1990, only a fraction of these had Internet connectivity. Just 15 years later, almost half of them had persistent broadband connections.[5]
Inefficient address use
Organizations that obtained IP addresses in the 1980s were often allocated far more addresses than they actually required, because the initial allocation method was inadequate to reflect reasonable usage. For example, large companies or universities were assigned class A address blocks with over 16 million IPv4 addresses each, because the next smaller allocation unit (Class B network) was too small for their intended deployments. Some of these allocations were never used, and some of the organizations that received them have diminished in size, while other organizations then left out have expanded.
Many organizations continue to utilize public IP addresses for devices not accessible outside their local network. From a global address allocation viewpoint, this is inefficient in many cases, but scenarios exist where this is preferred in the organizational network implementation strategies.
Due to inefficiencies caused by subnetting, it is difficult to use all addresses in a block. The host-density ratio, as defined in RFC 3194, is an intuitive metric for utilization of IP address blocks.
Virtualization
With advances in hardware performance and processor features of server systems and the advent of sophisticated hardware abstraction layers it became possible to host many virtual instantiations of an operating system on a single computer. Each of these systems may require a public IP address.

Efforts of mitigation

Some methods of mitigation of IPv4 address exhaustion have been

Subnetting is a popular method of managing and subdividing address space, thereby reducing additional allocations for expanding networks.

A few organizations have returned large blocks of IP addresses. Notably, Stanford University relinquished their Class A IP block in 2000, making 16 million unused IP addresses available.[6] Such a massive undertaking only postponed the inevitable exhaustion by less than a month. This is an example of the futility of efforts to save addresses. In the mean time, most users have to deal with the limited availability of IP addresses, which is limiting them in ways they usually do not even realize. Moreover, most parties have waited for, or are waiting with their switch until exhaustion anyway, this has had only a minimum impact on the ease of the transition.

Exhaustion date

IPv4 adresses exhaustion since 1995.
IPv4 addresses allocation rate per RIR.

Estimates of the time of complete IPv4 address exhaustion varied widely in the early 2000s, but all converge now on the time frame from 2011 to 2012. As of October 2010 predictions of exhaustion date of the unallocated IANA pool seem to converge to between January 2011[7] and January 2012.[8] In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last for one or two decades.[9] In September 2005, a report by Cisco Systems suggested that the pool of available addresses would dry up in as little as 4 to 5 years.[10] As of May 2009, a daily updated report projected that the IANA pool would be exhausted in June 2011, with the various regional Internet registries using up their allocations from IANA in March 2012.[11] As of 2008, a policy process has started for the end-game and post-exhaustion era.[12]

Exhaustion will first occur at IANA, then at APNIC, and then at the other RIRs. Only specific organizations that requested addresses in the pre-CIDR or pre-RIR eras possibly have significant unused address space remaining.

The most prominent analysis of the exhaustion progress is published by Geoff Huston, Chief Scientist at APNIC. As of August 2010, his daily IPv4 Address Report predicts the exhaustion date of the unallocated IANA pool for May 2011.[13] Huston's predictions are derived from past and current allocation trends and policies by IANA and the regional Internet registries (RIR). Two other regularly updated sites, those of Tony Hain, and Stephan Lagerholm, roughly agree with him as of August 2010.

After the IANA pool exhaustion, each RIR will be able to supply from their last assigned addresses for another 8 months after IANA exhaustion, when at least one of the RIRs is expected to be depleted. At this point hosts will appear on the Internet that are only addressable by IPv6. Currently, IPv4 allocations are accelerating, resulting in exhaustion trending to earlier dates. By early 2012, there will be new devices and services on the Internet only reachable by IPv6. For the rest of the Internet to be able to communicate with them, older hosts must implement IPv6 as well, or they must utilize special translator gateway services.

The time remaining until the first RIR exhaustion is a short time for the entire industry to transition to IPv6. This situation is aggravated by the likelihood that until exhaustion there will be no significant demand for IPv6. David Conrad, the general manager of IANA, acknowledges: "I suspect we are actually beyond a reasonable time frame where there won't be some disruption. Now it's more a question of how much."[citation needed] Geoff Huston claims the transition to IPv6 should have started much earlier, such that by the exhaustion date it would be completed, with all devices IPv6-capable, and IPv4 being phased out.

Notable exhaustion advisories

  • On May 21, 2007, the American Registry for Internet Numbers (ARIN), the North American RIR, advised the Internet community that due to the expected exhaustion in 2010 "migration to IPv6 numbering resources is necessary for any applications which require ongoing availability from ARIN of contiguous IP numbering resources".[14] "Applications" includes general connectivity between devices on the Internet, as some devices only have an IPv6 address allocated.
  • On June 20, 2007, the Latin American and Caribbean Internet Addresses Registry (LACNIC), the South American RIR, advised "preparing its regional networks for IPv6" by January 1, 2011, for the exhaustion of IPv4 addresses "in three years time".[15]
  • On June 26, 2007, the Asia-Pacific Network Information Centre (APNIC), the RIR for the Pacific and Asia, endorsed a statement by the Japan Network Information Center (JPNIC) that to continue the expansion and development of the Internet a move towards an IPv6-based Internet is advised. This with an eye on the expected exhaustion around 2010 which will create a great restriction on the Internet.[16][17]
  • On April 15, 2009, the American Registry for Internet Numbers (ARIN), the North American RIR, sent a letter to all CEO/Executives of companies who have IPv4 addresses allocated informing them that ARIN expects the IPv4 space will be depleted within the next two years.[18]
  • On 25 August 2009 ARIN announced a joint series event in the Caribbean region to push for the implementation of IPv6. ARIN reported at this time that less than 10.9% of IPv4 address space is remaining.[19]
  • Tony Hain of networking equipment manufacturer Cisco Systems predicts the exhaustion date of the unallocated IANA pool to be around September 2011 (updated monthly).[20] His predictions currently[when?] closely track Geoff Huston's.

Endgame

Reclamation of unused IPv4 space

Before and during the time when classful network design was still used as allocation model, large blocks of IP addresses were allocated to some organizations. IANA could potentially reclaim these ranges and reissue the addresses in smaller blocks.[citation needed] However, it can be expensive in terms of cost and time to renumber a large network, so these organizations will likely object, with legal conflicts possible.[citation needed] However, even if all of these were reclaimed, it would only result in postponing the date of address exhaustion.

Similarly, IP address blocks have been allocated to entities that no longer exist or never used them. No strict accounting of IP address allocations has been undertaken, and it would take quite a bit of effort to track down which addresses really are unused, as many are only in use on intranets.[citation needed]

ARIN has a transfer policy, such that addresses can get returned to ARIN, with the purpose to be reassigned to a specific recipient.[citation needed]

Some address space that was previously reserved by IANA has been added to the available pool. There have been proposals to use the class E network addresses,[21][22] but many computer and router operating systems and firmware do not allow the use of these addresses.[23][24][25][26][27] For this reason, the proposals have sought not to designate the class E space for public assignment, but instead propose to permit private use for networks that require more address space than is currently available through RFC 1918.

ISP-wide NAT

In the same way that a company can use NAT for most employee computers, an ISP can use NAT for many of its customers, instead of giving each a publicly routable IP address.[28]

This has been successfully implemented in some countries like Russia, where many broadband ISPs now have ISP-wide NAT in place, with an option of assigning a publicly routable IP address at an additional cost.[citation needed]

However, ISP-wide NAT has many limitations, including scaling problems in that it may not work effectively with a large number of connections. In addition, not all applications are suitable for use with all NAT boxes, such as Windows Networking, Netmeeting and SIP.[citation needed]

Markets in IP addresses

The creation of markets to buy and sell IPv4 addresses has been proposed many times as an efficient means of allocation. The primary benefit of an address market would be that IPv4 addresses would continue to be available, although the market price of addresses would be expected to rise over time. These schemes have major drawbacks that have prevented their implementation, as outlined in RFC 2008:

  • The creation of a market in IPv4 addresses would only delay the practical exhaustion of the IPv4 address space for a relatively short time, since the public Internet is still growing. This implies that absolute exhaustion of the IPv4 space would follow within at most a couple of years after the exhaustion of addresses for new allocations.
  • The concept of legal "ownership" of IP addresses as property is explicitly denied by ARIN and RIPE policy documents and by the ARIN Registration Services Agreement. It is not even clear in which country's legal system the lawsuits would be resolved.
  • The administration of such a scheme is outside the experience of the current regional address registries.
  • Ad-hoc trading in addresses would lead to fragmented patterns of allocation that would vastly expand the global routing table, resulting in severe routing problems for many network operators which still use older routers with limited FIB memory or low-powered routing processors. This large cost placed on everyone who uses the Internet by those that buy/sell IP addresses is a negative economic externality that any market would need to correct for.
  • Trading in IP blocks that are large enough to prevent fragmentation problems would reduce the number of potentially tradeable units to a few million at most.
  • The cost of changing from one set of IP addresses to another is very high, reducing the market liquidity. Organizations that can potentially reorganize their usage of IP addresses to free them up so that they can be sold will demand a high price and, once bought, will not be resold without a large profit. The cost of renumbering an organization's IP address space each time is comparable to the cost of switching to IPv6 once.[citation needed]

Long-term solution

IPv6 is currently the only viable solution to the IPv4 address shortage, endorsed and implemented by all Internet technical standards bodies and network equipment vendors. In addition to other design improvements, it replaces the 32-bit IPv4 address (4.3×109 or 4.3 billion possible addresses) with a 128-bit address for a theoretical capacity of 3.4×1038 addresses. IPv6 has been in active production deployment since June 2006, when organized worldwide efforts of testing and evaluation ceased (6bone).

References

  1. ^ RFC 4632 - Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan | The Internet Society 2006
  2. ^ a b Niall Richard Murphy, David Malone (2005). IPv6 network administration. O'Reilly Media, Inc. pp. xvii–xix. ISBN 0596009348.
  3. ^ Global IPv6 Statistics - Measuring the current state of IPv6 for ordinary users, S.H. Gunderson (Google), RIPE 57 (Dubai, Oct 2008)
  4. ^ Broadband adoption passes halfway mark in U.S. | CNET News.com
  5. ^ Projections of the Number of Households and Families in the United States: 1995 to 2010
  6. ^ Marsan, Carolyn. "Stanford move rekinds 'Net address debate". Network World. Retrieved 2010-06-29.
  7. ^ Hain, Tony. "IPv4 Address Pool, quarterly generated" (PDF). Retrieved 2010-10-06.
  8. ^ Huston, Geoff. "IPv4 Address Report, daily generated". Retrieved 2010-10-06.
  9. ^ Exec: No shortage of Net addresses By John Lui, CNETAsia
  10. ^ A Pragmatic Report on IPv4 Address Space Consumption by Tony Hain, Cisco Systems
  11. ^ IPv4 Address Report
  12. ^ Proposed Global Policy for the Allocation of the Remaining IPv4 Address Space
  13. ^ Huston, Geoff. "IPv4 Address Report, daily generated".
  14. ^ "ARIN Board Advises Internet Community on Migration to IPv6" (Press release). American Registry for Internet Numbers (ARIN). 2007-05-21. Retrieved 2007-07-01.
  15. ^ "LACNIC announces the imminent depletion of the IPv4 addresses" (Press release). Latin American and Caribbean Internet Addresses Registry (LACNIC). 2007-06-21. Retrieved 2007-07-01.
  16. ^ "JPNIC releases statement on IPv4 consumption" (Press release). Asia-Pacific Network Information Centre (APNIC). 2007-06-26. Retrieved 2007-07-01.
  17. ^ "About IPv4 address exhaustion in Internet Registries" (PDF) (Press release) (in Japanese). Japan Network Information Center (JPNIC). 2007-06-19. Retrieved 2007-07-01.
  18. ^ Notice of Internet Protocol version 4 (IPv4) Address Depletion
  19. ^ White, Lauren (2009-08-25). "ARIN and Caribbean Telecommunications Union Host Premier Internet Community Meeting". Archived from the original on 2009-08-27. Retrieved 27 August 2009. The global Internet community is playing a crucial role in the effort to raise awareness of IPv4 depletion and the plan to deploy IPv6, as only 10.9% of IPv4 address space currently remains. {{cite news}}: Cite has empty unknown parameters: |trans_title= and |coauthors= (help)
  20. ^ Hain, Tony. "IPv4 Address Pool, monthly generated" (PDF). Retrieved 2008-05-15.
  21. ^ Wilson, Paul. "Redesignation of 240/4 from "Future Use" to "Limited Use for Large Private Internets" (expired draft)". Retrieved 2010-04-05. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  22. ^ Reclassifying 240/4 as usable unicast address space (expired draft)
  23. ^ "Address Classes". Windows 2000 Resource Kit. Microsoft. Retrieved 2007-11-14.
  24. ^ Hain, Tony. "A Pragmatic Report on IPv4 Address Space Consumption". Retrieved 2007-11-14.
  25. ^ van Beijnum, Iljitsch. "IPv4 Address Consumption". Retrieved 2007-11-14.
  26. ^ "TCP/IP Overview". Cisco Systems, Inc. Retrieved 2007-11-14.
  27. ^ "Intel Express 10 Switch TCP/IP Basics". Intel Corporation. Retrieved 2007-11-14.
  28. ^ draft-nishitani-cgn Common requirements for IP address sharing schemes.
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