Kent,

If you have an IPv6 capable host, why use "IPv4 compatible" addresses? Why not use an algorithmic translation that includes a provider prefix? It would seem to me that any IPv6 host should have the capability to algorithmically translate its IPv4 address, preferably dynamically.

IPv4 compatible addresses are needed to allow IPv6 communication across IPv4 only "cloud". This way a router at the border between "dual" (IPv6/IPv4) part of a network and IPv4 only part of the network can determine packet's destination by just looking at the low order 32 bits of the IPv6 destination address (the IPv4 address is needed to figure out how to tunnel the packet across the IPv4 only part of the network). An alternative would be to maintain a static mapping on the router (and this is a not an easy manageable proposition). Yakov. P.S. Perhaps this discussion is a bit outside the scope of this list, so we should either (a) continue this in private, or (b) move it to the IPng mailing list.