IPv6 provides a replacement for IPv4. IPv6 includes support for flow Identity in the packet header, which can be used to identify flows and improve QoS (Quality of Service). However, the primary reason for developing IPv6 was the requirement for IP address space. As such, IPv6 uses 128bits for addressing, as opposed to IPv4 which uses 32bits. This provides a colossal amount of address space. IPv6 was formerly known as IPng (next generation).