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Written by: Steve Wolfsohn
Written on: June 27th, 2011
Tags: computer science, electrical engineering, communication
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About the Author
Steve Wolfsohn is a junior at the University of Southern California, majoring in biomedical engineering with an electrical emphasis and a minor in video game design and management. He hopes to find a way to combine his passions of interactive entertainment and biomedical engineering.
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Volume XIII Issue III > No Vacancy: IPv4 Address Depletion and Possible Solutions for the Expanding Internet
Internet Protocol (IP) addresses form the foundation of the internet. Every device and website requires an IP address to send and receive information. Unfortunately, IPv4, the current IP address system, is limited to approximately 4 billion possible addresses, a threshold that is quickly approaching as countless new devices connect to the internet. When no IPv4 addresses are left, new devices and websites will be unable to access the internet. Temporary solutions such as IP address sharing in business and home networks have helped slow the depletion of IPv4 addresses, but the only true solution to this problem is the full implementation of IPv6, a new protocol that allows for an essentially limitless pool of unique addresses. The transition between these two incompatible systems has been slowed due to costs and lack of incentive, but now that IPv4 addresses are truly running out, the internet community at large is moving to complete the transition within the next decade. If all goes as planned, individual users will not notice any change; IPv6 will simply expand the internet to continue to provide access to more people around the world.

Is the Internet Full?

From entertainment to business, the internet is an undeniably fundamental part of society. Internet access connects the world, driving economies and spreading knowledge. Because the internet enables freedom of expression and promotes societal progress, the United Nations declared internet access a human right in May 2011 [1]. After growing without bound in the last two decades, it is hard to imagine any limits on the internet’s size. This perception, however, could be shattered as the internet may soon be forced to close its doors to new websites and devices.
In order to send or receive any data on the internet, each device or website needs a unique Internet Protocol (IP) address to identify itself, and the pool of IP addresses is rapidly depleting. As advances in technology enable millions of devices to connect to the internet in new and sophisticated ways, these devices may actually be unable to connect simply because they lack an IP address. Perhaps more detrimentally, developing third world businesses could be cut off from the internet access required for competition in the global economy. Thankfully, engineers are aware of this impending issue and are rapidly preparing solutions. As the world continues to develop, however, IP address depletion still poses a global problem.

IP Addresses Demystified

Before explaining IP address depletion, it is important to understand how IP addresses work and what purpose they serve. It may be simplest to think of IP addresses as phone numbers for the internet. Just as your phone has a unique code that allows others to contact you out of a sea of billions, each internet-capable device or website has a unique IP address to direct data to the correct location in the nearly infinite reaches of the internet. When you send data from your computer to a website, it is marked with the IP address of the target site so your computer knows where the data should go. In addition, your computer tags the data you send with your IP address so the website may respond properly. This system is represented in the Figure below (Fig. 1).
Steve Wolfsohn/Illumin
Fig.​ 1: IP addresses in internet navigation, depicting the process of sending data to a website and receiving a response.
IP addresses are not usually visible to the average user and are hidden by a system of domain names such as "illumin.usc.edu," which acts as a interface for internet users. When you enter a website’s domain name, your computer automatically looks up and uses the proper IP address to access the website. It is possible to bypass domain names and navigate by IP addresses alone: simply type http://128.125.124.9​3/ into your browser to see an IP address in action.
IP addresses themselves are not complicated. Like a phone number, they are simply a sequence of digits. Unlike phone numbers, however, IP addresses contain only ones and zeroes, and are 32 digits, or bits, in length. These 32 bits form four groups of eight, each known as a byte. A byte of data, when translated from binary, can represent a value between 0 and 255 (Fig. 2).
[image=803 file="IPAddress_2-17​5x176.jpg" placement="left"]Fig​. 2: IP address representations. The 32-bit address is translated into traditional numbers byte by byte. To simplify internet navigation, each website is assigned a domain name, which is matched with the proper IP address on a registry. [/image]

Internet Protocol Versions

IP addresses are just one aspect of the overall internet protocol, which also contains regulations for security and technical details. The current internet protocol is version 4 (IPv4). Versions 1 through 3 were merely drafts that never gained widespread use, and version 5 exists as an experiment and will not be implemented [2]. Created in 1983, during the early phases of the internet, IPv4 allows over 4 billion unique addresses to be in use [3]. At a time when only a few thousand devices were connected to the internet, and these were only operated by research institutions and the government, 4 billion addresses seemed more than sufficient. Unfortunately, with a global population of over 6 billion, there are not enough IP addresses for every person on Earth in an age when internet access is becoming a vital component of life. This is compounded by the fact that the internet has grown far beyond what pioneers could have imagined, with many individuals using not one, but multiple internet-capable devices such as family computers, personal laptops, gaming consoles, and phones [3]. The lack of new IPv4 addresses could, therefore, effectively shut out new devices or websites, including smart phones, community computers in a developing nation, or small business homepages.

Global IP Address Distribution

The Internet Assigned Numbers Authority (IANA) is a global body that divides IP addresses among regional internet registries (RIRs), as presented below (Fig. 3). RIRs, in turn, coordinate IP addresses in their regions and ensure that no two devices receive the same address by mistake [4]. Each RIR is directly responsible for selling and distributing IP addresses to customers such as Internet Service Providers (ISPs) or governments and large institutions in its geographic area.
Asia Pacific Network Information Center
Fig. 3: Global regional internet registry (RIR) map, showing the locations and logos of the 5 RIRs.
In the past, if an RIR had no IP addresses available, it could request more from IANA. However, on February 3rd, 2011, IANA issued the remaining IPv4 addresses, leaving the RIRs to operate on a limited pool of addresses for their regional customers. ARIN, the RIR for North America, has implemented restrictions on the number of addresses it will sell and maintains a countdown on its homepage for the number of remaining North American IPv4 addresses [5]. More alarmingly, the RIR for the Asian-Pacific region exhausted all but a small reserve of its IPv4 addresses by April of 2011, little more than two months after receiving its final allotment from IANA, and can no longer sell new IPv4 addresses to most customers [6]. The remainder of the RIRs are expected to run out of IPv4 addresses by 2013 [7].