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Internet Protocol Version 6 (IPv6) is a version of the IP protocol which supports 128-bit IP addresses. It has been developed as the next generation protocol to increase the 4 billion IP Addresses available and it will eventually replace the nearly exhausted IPv4, which supports 32-bit address space.[1] IPv6 has been developed to provide advantages over the current internet protocol. It is expected to solve several network problems by eliminating the need for Network Address Translation (NAT).

In late December 2015, IPv6 reached 10% adoption worldwide. [2] Late december 2019 it reached around 30% adoption worldwide, according to measurements by Google.


As early as 1990, internet experts predicted that the 4 billion available IP addresses under the IPv4 would not be enough to accommodate the rapid growth of internet users worldwide. During the Internet Engineering Task Force Meeting (IETF) in Vancouver in 1990, Phil Gross, Chairman of the Internet Steering Group (IESG), together with Frank Solensky and Sue Hares, noted that the Class B space will be exhausted as early as March, 1994. The solution to the problem was to assign multiple Class C address.This expansion signaled a great problem, which meant deciding whether to limit the size and growth rate of the Internet or to disrupt the network by changing to new strategies or technology.[3]

In 1991, the Internet Architecture Board (IAB) recommended the need for additional address flexibility. Based on this recommendation, the Internet Engineering Task Force formed the Routing and Addressing (Road) Group to examine the consumption of address space and the exponential growth in inter-domain routing entries.[4] The Road Group enumerated three possible serious problems, which include:[5]Exhaustion of the class B network address space, Growth of routing tables in Internet routers beyond the ability of current software, hardware, and people to effectively manage it, and eventual exhaustion of the 32-bit IP address space. It also recommended immediate and long term solutions which included the adoption of CIDR route aggregation proposal, reducing the growth rate of routing table, and called for proposals "to form working groups to explore separate approaches for bigger Internet addresses."[6]

In 1993, IETF formed the Internet Protocol Next Generation Group to evaluate the proposals and determine how to proceed in selecting a successor to IPv4. THe group evaluated and reviewed the proposals of CATNIP, SIPP and TUBA. After numerous discussions, the Directorate recommended the adoption of Simple Internet Protocol Plus (SIPP) Spec.128 bit version as the basis for the next generation of Internet Protocol. The version number 6 was assigned by IANA and it was officially called IPv6.[7]

IPv6 Working Group

The IPv6 Working Group was created by the IESG to implement the recommendations of the Internet Protocol Next Generation's Directors set forth during the IETF meeting in July, 1994, as described in RFC 1752 entitled, The Recommendation for the IP Next Generation Protocol. The IPv6 working group's primary role is to oversee the specification and standardization of IPv6.[8]

IPv6 Features & Benefits

IPv6 has the following features and benefits:[9] [10]

  1. Expanded addressing capabilities of 128 bits, a larger number of addressing nodes and a simpler auto configuration of addresses.
  2. Simplified header for routing efficiency and performance
  3. Improved Support for Extensions and Options
  4. Flow Labeling Capability
  5. Authentication and Privacy Capabilities
  6. Deeper hierarchy and policies for network architecture flexibility
  7. Efficient support for routing and route aggregation
  8. Serverless autoconfiguration, easier renumbering, multihoming, and improved plug and play support
  9. Security with mandatory IP Security (IPSec) support for all IPv6 devices
  10. Improved support for Mobile IP and mobile computing devices (direct-path)
  11. Enhanced multicast support with increased addresses and efficient mechanisms

IPv6 Address Notation Vs IPV4 Address Notation

Consider the following for example, the IPv4 address "" may appear in IPv6 notation as "0000:0000:0000:0000:0000:0000:C0A8:6420" or "::C0A8:6420".

An IPv6 address is written in hexadecimal quartets separated by colon for example: 2001:cdba:1900:0000:0000:0000:1757:3618 If there is a four-digit group of zeroes within an IPv6 address, it can be reduced to a single zero and delete the group of 4 zeroes and the address can be written as:2011:cdba:1900:0:0:0:1757:3818 or 2001:cdba:1900:3257:9652[11]

The most obvious benefit of IPv6 is the exponentially greater number of IP addresses it can support compared to IPv4. Many countries outside the U.S. suffer from a shortage of IP addresses today. Because IPv6 and IPv4 protocols coexist, those locales with an address shortage can easily deploy new IPv6 networks that work with the rest of the Internet. Experts believe it will take many more years before all networks fully change over to IPv6.

Other benefits of IPv6 are less obvious but equally important. The internals of the IPv6 protocol have been designed with scalability and extensibility in mind. This will allow many different kinds of devices besides PCs, like cell phones and home appliances, to more easily join the Internet in future.

Types of IPv6 Addresses

IPv6 supports the following three IP address types:

Unicast and multicast messaging in IPv6 are conceptually the same as in IPv4. IPv6 does not support broadcast, but its multicast mechanism accomplishes essentially the same effect. Multicast addresses in IPv6 start with 'FF' (255) just like IPv4 addresses.

Anycast in IPv6 is a variation on multicast. Whereas multicast delivers messages to all nodes in the multicast group, anycast delivers messages to any one node in the multicast group. Anycast is an advanced networking concept designed to support the failover and load balancing needs of applications.

IPv6 reserves just two special addresses: 0:0:0:0:0:0:0:0 and 0:0:0:0:0:0:0:1. IPv6 uses 0:0:0:0:0:0:0:0 internal to the protocol implementation, so nodes cannot use it for their own communication purposes. IPv6 uses 0:0:0:0:0:0:0:1 as its loopback address, equivalent to in IPv4.

Also Known As: IPng (Internet Protocol Next Generation)

IPv6 Special Addresses

The next generation Internet Protocol version 6 has special addresses, which include:[12]

  • ::/96 -is a zero prefix denoting the addresses compatibility with the previously used IPv4 protocol.
  • ::/128 -is an IPv6 address with all zeroes in and is referred to as an unspecified address and is used for addressing purposes within a software.
  • ::1/128 -referred as loop back address and is used to refer to the local host. An application sending a packet to this address will get the packet back after it is looped back by the IPv6 stack. The local host address in the IPv4 was
  • 2001:db8::/32 -is the official documentation prefix allowed by IPv6 which denotes that the address is only an example
  • fec0::/10 -is a site-local prefix offered by IPv6 which implies that the address is valid only within the local organization.The use of this prefix is discouraged by RFC
  • fc00::/7 -referred as the Unique Local Address, which are routed only within a set of cooperating sites. It was introduced to replace the site-local addresses and provides a 40-bit pseudorandom number which lessens the risk of address conflicts.
  • ff00::/8 -is a prefix used to automatically denote a multicast address
  • fe80::/10 -is a link-local prefix offered by IPv6 signifying that the address is valid only in the local physical link.

IPv6 Forum

On July 17, 1999, the IPv6 Forum, a non-profit organization, was established and composed of international Internet vendors, Industry Subject Matter Experts, and Research & Education Networks to help educate and inform the global Internet community regarding the importance of deploying the IPv6.[13]

IPv6 Deployment

In December, 1995, IANA formally assumed the responsibility of the address management functions of IPv6; subsequently, in 1996, the IPv6 standard was completed, in 1999 its production allocation was made available to ISPs. The early phase of IPv6 deployment started in 2000 using tunneling techniques over a common IPv4 layer. Google and Comcast were among the large Internet operators deploying IPv6 at the time.[14] By mid 2007, public interest on the use of IPv6 increased based on the Autonomous System routing table. Between 2004 to 2008, IPv6 routes increased from 2.5 % TO 3%. As of 2008, the size of IPv6 deployment in terms of host capability is between 2-3 per one thousand Internet hosts.[15]

ICANN's IPv6 Global Allocation Policy

On July 16, 2006, ICANN released its policy statement regarding the allocation of IPv6 address space, which include:[16]

  • The unit of IPv6 address space allocation from IANA will be /12. A sufficient number of address space will allocated to every Regional Internet Registries to support their registries needs for 18 months. Each RIR will be responsible for choosing their own allocation reservation strategies to ensure effective and efficient work.
  • Every RIR with less than /12 of un-allocated address space will receive an IPv6 allocation from IANA following ICANN's implementation of the IPv6 Address Space Global Allocation Policy.
  • Any RIR will be eligible for an additional allocation of IPv6 address space if an RIR has less than 50% of the /12 and an RIR's IPv6 address space is less than its established necessary space for the next 9 months period. In this situation IANA will make a single IPv6 allocation to meet the RIR's established address space for 18 months.
  • The allocation of IPV6 addresses to an RIR should be announced and updated by IANA, and the National Resource Organization (NRO, the coordinating body for the 5 RIRs responsible for distributing IP addresses and AS numbers), and each RIR's respective website. The administrative procedures to manage this process will be handled by ICANN and the NRO.

Google Experiment on IPv6

The experiment conducted by Google on IPv6 end-user connectivity and traffic levels in 2009 found that:[17]

  • 0.25% of users were IPv6 capable as September 2009 and half of the users were using MacOS and Windows Vista
  • 0.9% of end-users using other technically oriented websites were connected to IPv6 when possible as of June, 2009
  • Leading countries countries capable of using IPv6 as of September 2009 were France (1%), China (0.4%), Sweden (0.2%), Japan, Netherlands and United States (less than 0.1%)
  • Networks originating majority of IPv6 traffic come from universities and research institutions with the exemption of free.fr, a French IPv6 enabled ISP.

IPv4 Final Depletion

On February 3, 2011, ICANN along with the Number Resources Organization (NRO), the Internet Architecture Board (IAB) and the Internet Society (ISOC) informed the global Internet community that the remaining IPv4 addresses were all allocated by the Internet Assigned Names and Numbers (IANA) to the Regional Internet Registries (RIRs). ICANN's President and CEO at the time, Rod Beckstrom, noted that IPv6 adoption is very important and the Internet technical community had been planning and working for a long period of time to deploy IPv6 when IPV4 addresses are completely depleted. In addition, Raúl Echeberría, Chairman of the NRO, emphasized that “deploying IPv6 is now a requirement, not an option".[18]

World IPv6 Day

On June 8, 2011, ISOC led the World IPv6 Day, a global trial of the deployment of the IPv6 ; 400 organizations such as Google, Facebook, Yahoo!, Akamai and Limelight Networks participated. The participants enabled IPv6 on their primary service for 24 hours to find out the potential challenges related to using the new Internet protocol. Based on the result of the trial, services were accessed normally by the majority of the Internet users; however, there were some cases wherein users experienced difficulty in accessing the services of some of the participants.[19]

According to John Curran, chief executive of the American Registry for Internet Numbers (ARIN), the trial was successful. Rob Malan, chief technology officer of Arbor Networks, also noted that the test went without major problems. Some analysts believe that potential problems may occur when companies start to actually use the new protocol in the next few years as IPv4 and IPv6 need to co-exist for a period of time. Some experts are also concern about Internet security issues, citing that there are no standards in the process of encapsulation, a technology used to enable IPv4 and IPv6 sites to communicate with each other during the transition period.[20]