Internet Protocol version 6 (IPv6), also called IP Next Generation (IPng), is the second-generation standard protocol of network layer protocols. As a set of specifications defined by the Internet Engineering Task Force (IETF), IPv6 is the upgraded version of Internet Protocol version 4 (IPv4).
The most significant difference between IPv6 and IPv4 is that IP addresses are lengthened from 32 bits to 128 bits. Featuring a simplified header format, sufficient address space, hierarchical address structure, flexible extended header, and an enhanced neighbor discovery (ND) mechanism, IPv6 has a competitive future in the market.
IP technology has become widely applied due to the great success of the IPv4 Internet. As the Internet develops, however, IPv4 weaknesses have become increasingly obvious in the following aspects:
The IPv4 address space is insufficient.
An IPv4 address is identified using 32 bits. In theory, a maximum of 4.3 billion addresses can be provided. In actual applications, less than 4.3 billion addresses are available because of address allocation. In addition, IPv4 address resources are allocated unevenly. The USA occupies almost half of the global address space, Europe uses fewer IPv4 addresses, whereas the Asian-Pacific region uses an even smaller quantity. The shortage of IPv4 addresses limits further development of mobile IP and bandwidth technologies that require an increasing number of IP addresses.
Classless Inter-domain Routing (CIDR) is the typical solutions to IPv4 address exhaustion. There are several solutions to IPv4 address exhaustion. CIDR, however, has its disadvantages, which helped encourage the development of IPv6.
The backbone router maintains too many routing entries.
In the initial IPv4 allocation planning, many discontinuous IPv4 addresses were allocated, and therefore routes cannot be aggregated effectively. The constantly growing routing table consumes significant memory, affecting forwarding efficiency. Subsequently, device manufacturers have to upgrade routers to improve route addressing and forwarding performance.
Address auto configuration and readdressing cannot be performed easily.
An IPv4 address only has 32 bits, and IP addresses are allocated unevenly. Consequently, IP addresses must be reallocated during network expansion or replanning. Address autoconfiguration and readdressing are required to simplify maintenance.
Security cannot be guaranteed.
As the Internet develops, security issues have become more serious. Security was not fully considered in designing IPv4. Therefore, the original framework cannot implement end-to-end security. An IPv6 packet contains a standard extension header related to IP security (IPsec), which allows IPv6 to provide end-to-end security.
IPv6 solves the problem of IP address shortage and has the following advantages:
With so many obvious advantages over IPv4, IPv6 has developed rapidly.