IPv6 is the last version of the IP protocol, developed to replace the IPv4, which is running out of free IP addresses. That is because the IPv4 uses only 32 bits for Internet addresses, so it can support just 2^32 addresses, while the IPv6 uses 128 bits for its IP addresses and supports 2^128. That makes up for much bigger address space that is not likely to run out of addresses. IPv6 not only provides much more IP addresses, but it also improves on some of the IPv4 features: it offers different, more efficient packet headers, stateless address autoconfiguration, integrated IPsec. An IPv6 address is represented via the hexadecimal system with four digits in eight groups separated with colons like this: 3001:0db8:85b3:0022:0000:8a2e:0310:7330.
The Transition From IPv4 To IPv6
To avoid big problems for the Internet we should gradually switch from the limited, but predominantly used IPv4 to IPv6. Although these two protocols are not very different from each other the transition can’t be done at once, because they are independent, parallel networks that aren’t compatible and communicate with each other only via special gateways and tunneling. Servers, routers, and computers (most recent operating systems already support IPv6) also need to be modified to support both protocols if they want to access both IPv4 and IPv6 addresses. Most of these devices could be updated solely with software and firmware upgrades. However, these updates won’t be always possible and will require money and time. For now, only a small percentage of all Internet networks support IPv6.