Internet Protocol version 6 (IPv6) is designated as the successor to IPv4, with the main driving force for its design being the expected depletion of the IPv4 public address space. The standard is specified in RFC2460: Internet Protocol, Version 6 (IPv6) Specification.
Where IPv4 uses 32 bit addresses IPv6 uses 128 bits, resulting in an immensely larger address space than IPv4 (around 79 octillion times the IPv4 address space), with the IPv6 subnet size standardised at 64 bits.
This expanded address space eliminates the primary need for network address translation (NAT), from the network design point of view, as increased flexibility in IP address allocation and routing is provided by IPv6.
As well as increased IP address space IPv6 provides several key benefits over IPv4, including:
- simpler packet headers - IPv6 specifies a new packet format, designed to minimise packet-header processing
- IPv6 provides better capabilities to support auto-configuration, such as Dynamic Host Configuration Protocol (DHCP), multicasting, traffic engineering, and zero configuration networking
- mandatory Internet Protocol security (IPsec) support - IPsec was originally developed for IPv6