IPv4/IPv6 over Firewire, Reworked (cont'ed)

• Changing the L2 hardware address format allows us to have direct map between IPv6 multicast addresses and L2 addresses.

• If “multicast” bit (the lowest bit of the first octet) is on, send the packet via GASP
• IPv6 multicast address is in ff00::/8, whose lowest bit of the first octet is set.
• IPv4 can be mappe d as 01:00:00:...:00:xx:xx:xx:xx, for example.
• Otherwise, it is L2 unicast; use the additional information embedded in the destination (virtual) hardware address to send.

• Note: All multicast adresses are mapped as L2 broadcast (ff:ff:...:ff) so far.

• In fact, MCAP is almost broken. Broadcast context is an expensive resource to allocate and it is not always available. Unless all of receivers can allocate the resource, sender cannot send multicast packet for that address via that channel.