IPv6 addresses consist of eight 16-bit words, that together form a single 128-bit address; IPv4 addresses consist of four 8-bit words resulting in a 32-bit address. The increased size of the IPv6 address greatly increases the number of available IP addresses. However, since the UnixWare IPv6 implementation runs over an IPv4 network, it implies that any IPv6 address must be able to be mapped directly onto an IPv4 address. This is done by using a special address called an ``IPv4 mapped IPv6 address''. The address has the following format:
0000:0000:0000:0000:0000:FFFF:x.x.x.xHere x.x.x.x is the valid IPv4 address. Currently, the
0000:0000:0000:0000:0000:FFFF: part
is prefixed or removed by an internal library routine to simulate the use of
IPv6 addresses. No IPv6 addresses currently pass
through the Network layer.