zone-index

IPv6 Zone index and scope_id

How does the zone index relate to the scope_id in the sockaddr_in6 structure? The functionality appears to differ between platforms and I'd love to know how they relate. Windows for example has a SCOPE_ID structure (as well as just a 32-bit value). Mac OSX only has a 32-bit value. Obviously the 32-bit value is the way to go but how e...