What is IPv6?
How does IPv6 differ from IPv4, and why was it developed? Start with the size of their address spaces and the ways networks assign addresses.
IPv6 (Internet Protocol version 6) was developed as the successor to IPv4, especially to expand the Internet's address space.
However, the main difference between them is the size of the IP address. IPv4 uses 32-bit addresses, allowing for around 4 billion unique addresses. On the other hand, IPv6 uses 128-bit addresses, which allows the creation of a much larger number of IP addresses, in the order of 3.4 x 10^38.
When was IPv6 born?
The IETF published the first IPv6 specification in RFC 1883 in 1995. RFC 2460 followed in 1998, and the current specification is RFC 8200. Calling 1998 the protocol's single launch date would obscure that history.
IPv6 was developed to meet the demands of a constantly growing Internet, with an ever-increasing number of connected devices. Since then, its adoption has been gradual but constant. Soon, many companies and organizations began upgrading their networks to support the new protocol.
How does it work?
IPv6 uses 128-bit addresses, while IPv4 uses 32-bit addresses. Its specification also defines a distinct packet header; encryption depends on additional protocols and network configuration. RFC 8200.
Imagine you live in a neighborhood where all the houses have address numbers limited to two digits. In this case, there can only be 99 houses in the neighborhood. As the population grows and more people want to move into the neighborhood, there will soon come a point when there are no more numbers available for new homes.
Now suppose the authorities decide to adopt a new addressing system in which each house can have a three-digit address number. With this new system, the neighborhood will be able to accommodate a much larger number of homes, up to 999.
That change illustrates the larger address space of IPv6. IPv4 has roughly 4.3 billion theoretical address combinations, some of them reserved; public address scarcity motivates NAT and IPv6 deployment.
Differences with IPv4
On a home network, NAT allows multiple devices to share one public IPv4 address. The global IPv4 address limit does not mean only one device can use the connection. IPv6 expands the address space and supports other assignment strategies.
IPv6 uses 128-bit addresses, compared with IPv4's 32 bits. Address assignment to interfaces depends on network policy and the available prefix. RFC 4291.
One of the main differences between IPv4 and IPv6 is the way addresses are written. While IPv4 uses a format of four octets separated by periods (for example, 192.168.1.1), IPv6 uses a format of eight groups of four hexadecimal digits separated by colons (for example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334).