IP address starvation

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IP address starvation refers to the decreasing availability of publicly available IPv4 IP addresses. This has been a concern that has spanned decades to the 1980s. As a result, this has been the driving factor in creating and adopting several new technologies, including classful networks, CIDR addressing, and IPv6.

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[edit] Synopsis

Every host on a network, such as a computer or networked printer, is assigned a unique IP address that is used to communicate with other hosts on that network normally expressed in dotted decimal format (for example 66.230.200.110). Each octet or part of the address, must be a number from 0 to 255 and therefore there is a logical maximum of 4,294,967,296 addresses available for use, however take into consideration that large numbers of addresses, those that start with 127 for example, are unavailable for use and the number of available addresses that can be used on the Internet is significantly less.

Clearly there are nowhere near enough IPV4 addresses on the public internet to provide one to each computer or other device requiring internet access, this problem is (largely) solved by network address translation (NAT), whereby a single public Internet IP address can be shared by multiple internal local area network (LAN) hosts. Data sent by individual hosts to the Internet states its source address as the public IP address used, and the router providing the access is able to keep track of which host originated the traffic inside the network and forward replies accordingly. This is a similar concept in a way to the manner in which multiple office telephones may all phone outwards through the one phone service, each having an extension number (for example 219) and only necessitating the use of a single phone number.

[edit] Causes

Today, there are several driving forces to the next address allocation solution:

[edit] China

With more than a little confusion and misconception, China is a country described as already having a "critical shortage" of IP addresses. This is almost entirely myth, APNIC[1] asserts that while sufficient IP addresses exist for the next 15 to 20 years, no 'blocks' of IP addresses are assigned to a particular geographic region or economy. China has the entire remaining unallocated IP address pool as potentially available for use; just like the rest of the world. This myth probably survives due to misinformed uncertainty about the size of China as a country and the recent stronger uptake of technology in its immense population.

[edit] Solutions

Some things that can be done to mitigate the IPv4 address exhaustion are (not mutually exclusive):

[edit] Conservation

"Conservation" is another method used to preserve available IP addresses, upon conception of the Internet it was never envisaged that it would require anywhere near as many IP addresses as it now does; therefore they were frequently allocated in 'blocks' of 255, 65536, or 16777216 addresses for use. To this day several organisations have been assigned 16 million IP addresses of which they use a comparative handful[2]. These days organisations responsible for allocation of public IP addresses are much more reluctant to assign large groups, and the establishment of a commercial market for them mean they are handed out with less abandon.

[edit] Subnetting

Subnetting is again another method used to get more use out of IP addresses generally, in short the dotted decimal notation is a user-friendly method of representing binary addresses such as 01000010111001101100100001101110 (again 66.230.200.110). These addresses are subnetted by applying a subnet mask which denotes which portion of the address is the network portion and which is the host portion; this is analogous to the area code and subscriber number of a telephone number, the phone number (212) 555-9293 is uniquely identifiable from (213) 555-9293. This allows the same numbers to be used in multiple locations with only some minor extra consideration.

[edit] IPv6 as a solution

IPv6 however, may be the only final alternative to the problem, instead of a 32 bit address, IPv6 represents addresses as 128 bit addresses, providing 3.4×1038 or logically 50 octillion for each of the roughly 6.5 billion people on Earth.

[edit] Reclaiming unused IPv4 space

In the early days of the Internet, before the creation of classful networks and later CIDR addressing, large blocks of IP addresses were allocated to individual companies and organizations. It is often suggested that these allocations should be reclaimed by IANA and reissued to others. However, it can cost a great deal of time and money to renumber a network so these organizations will likely object, quite possible to the point of filing lawsuits. Moreover, at the current rate of IPv4 address consumption, even if all of these could be reclaimed, it would result in only extend the address exhaustion date back a year or two.

Similarly, many IP address have been allocated to companies that no longer exist or were never used. Unfortunately, the stricter accounting of IP address allocation that currently in place wasn't always in place and it would take quite a bit of effort to track down which addresses really are unused. Many IP addresses that do not show up in the public BGP routing tables are actually in use on intranets. Again, it is likely that more time would be spent tracking down which IP address could be reclaimed than would extend the exhaustion date.

Finally, some have suggested using IP addresses that are currently reserved by IANA, such as the form class E network addresses. Unfortunately, there are many operating systems, routers and other software that would needed to be modified or upgraded in order for them to be usable. The effort to do this would likely be as much, if not more, than switching to IPv6.

[edit] Exhaustion date

As of March 2007, Geoff Huston of APNIC predicts with detailed simulations an exhaustion of the unallocated IANA pool in July 2011. Tony Hain of Cisco predicts the exhaustion date to be around March 2010. Even if allocation rates do not further accelerate, a highly unlikely scenario, exhaustion is expected in 2012. These predictions are derived from current trends, and do not take into account any last chance rush to acquire the last available addresses. After the IANA pool exhaustion, each individual RIR will be able to meet demand for about 11 months with their last assigned addresses. These dates lie within a depreciation time of five years of network equipment that is currently being acquired.

After this date, a market might develop for addresses. Note that the legality of address trading is questionable, since unused address space is supposed to be returned to the distributors IANA/RIR/LIR. It is furthermore not clear how much of about 46% of "non-advertised" address space can recovered, as part of it is planned to be used. Also, part of it is used in internal networks in companies where there are requirements to not overlap with other internal or public networks.

[edit] IPv6 ready?

IPv6 readiness is currently not considered in most purchasing decisions. If such equipment is not IPv6-capable, it might need to be upgraded or replaced prematurely if "native" connectivity to new users and servers using IPv6 addresses is required. Most equipment would be perfectly ipv6 capable with a software/firmware update. However, as with 64-bit windows and Wi-Fi_Protected_Access support, manufacturers might try to save on development cost for hardware which they are not selling anymore anyway, and try to get more sales from new "ipv6-ready" equipment. Moreover, as ipv6 gets implemented, optional features might become really important, such as ipv6 mobile. It is therefore important to check your suplier on its support record, and get guarantees if you can or need to. Examples of equipment which currently usually are not IPv6 ready, are home routers. As for the CableLabs consortium, the 160 Mbps DOCSIS 3.0 ipv6-ready specification for cable modems has only been issued in August 2006. It is expected that only 60% of cable modems' servers and 40% of cable modems will be IPv6-ready by 2011. Other equipment which is typically not ipv6-ready range from skype and sip phones to oscilloscopes. Professional network routers in use should be ipv6-ready. Most personal computers should also be ipv6-ready, because the network stack resides in the operating system. Most applications with network capabilities are not ready, but could be upgraded with support from the developers.

[edit] References

  1. ^ http://www.apnic.net/docs/apster/issues/apster12-200412.pdf
  2. ^ Alyssa P. Hacker (November 5th, 1995). IP Address Shortage Spurs Black Market. Massachusetts Institute of Technology. Retrieved on September 5, 2006.
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