Overview of IPv6 protocol along with various transition scenarios for the migration from IPv4 to IPv6
IPv6 is the current and future Internet Protocol standard. As anticipated, IPv4 addresses became exhausted around 2012.
The IP address scarcity is the main driver for IPv6 protocol adoption.
IPv6 defines a much larger address space that should be sufficient for the foreseeable future, even taking into account Internet of Things scenarios with zillions of small devices connected to the Internet.
IPv6 is, however, much more than simply an expansion of the address space. IPv6 defines a clean address architecture with globally aggregatable addresses thus reducing routing table sizes in Internet routers.
IPv6 extension headers provide a standard mechanism for stacking protocols such as IP, IPSec, routing headers and upper layer headers such as TCP.
ICMP (Internet Control Message Protocol) is already defined for IPv4. ICMP was totally revamped for IPv6 and as ICMPv6 provides common functions like IP address and prefix assignment.
Lack of business drivers for migrating to IPv6 is responsible for sluggish adoption of IPv6 in carrier and enterprise networks.
Numerous transition mechanisms were developed to ease the transition from IPv4 to IPv6. Many of these mechanisms are complex and difficult to administer.
The transition mechanisms can be coarsely classified into dual-stack, tunneling and translation mechanisms.