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Top1. Introduction
Internet Protocol Version 4 (IPv4) since its genesis has been pervasive even in today’s operational networks. The IPv4 protocol enabled the hosts to send packets to other hosts having a unique address. However, it was never designed to scale millions and billions of hosts online. The contributing factor in address depletion has been exponential increase in internet ready devices and origin of broadband wireless networks (Chen & Liao, 2017). The three decade old protocol with a limited address space cannot scale up to the ever demanding needs of present day internet. This limited address space got exhausted and raised an alarming issue over the growth of internetworks.
In late 80’s, IETF came up with the idea of using temporary internet patches like CIDR (classless inter-domain routing) and NAT (network address translation) for internet continuity. But in 1992, CIDR (classless inter-domain routing) design was put into operation and the number of internet nodes surpassed over 100,000 (Rekhter & Li, 1993; Fuller et al., 1993). Thus, these short term antidotes failed given the ever expanding nature of internet. Also, being an obsolete protocol, the distinctive attributes like mobility, security and QoS (Quality of Service) were supplemented by retrofitting such characteristics in IPv4. For example, Internet Protocol Security (IPsec) provides security for IPv4 packets at the network level using encryption mechanism. As IPsec is not an inherent component in IPv4, its implementation has compatibility issues with NAT (Kent & Seo, 2005). Although IPv4 ToS (type of service) and identification attributes provide support for real time data, but its implementation has a limited domain (only 8 bits).Also the term ToS has been polished over a number of times. IPv4 has also issues in payload identification when encryption is used on a TCP or UDP port address.
IETF in 1992 came to the conclusion that IPv4 was on the verge of exhaustion. The Internet Engineering Task Force (IETF) soon started the process of searching a more flexible solution by creating a temporary adhoc IP Next Generation (IPng) group to address the problems and issues of next internet protocol version. Consequently, a white paper solicitation was released for the Next Generation Internet Protocol which was followed by the release of several RFC’s related to IPv6 (Bradner & Mankin, 1993). Thus, after an exhaustive research and owing to the problems of address depletion, a new version of IP known as IPv6 was proposed and designed (Rekhter & Li, 1993).
In the initial stage, a migration from IPv4 to IPv6 was visualized which will help IPv6 hosts to maintain connectivity and reachability with IPv4 hosts (Gilligan & Nordmark, 2000). When an entire transition occurs, IPv4 will automatically be wiped out. However, given the current statistics, the migration to IPv6 is still underway. In fact, it is still in its initial stages as only average 7% of world population is using IPv6 as per Google 2015 statistics. It’s well understood that transition to IPv6 will be slow and gradual process overtime. The main rationale behind this being the massive deployment of NAT devices in enterprise and home networks which have acted as delaying catalyst in migration process. In fact, some people envisioned that the migration might even not occur. However as on Feb 3, 2011, the last block of IPv4 address space was allocated by the IANA (Internet Assigned Numbers Authority), thus declaring end of IPv4 addresses (Chen & Liao, 2017). Thus, adopting IPv6 makes an unblemished choice of replacement for IPv4.