On Jan 7, 2011, at 6:32 AM, Jack Bates wrote: > > > On 1/7/2011 4:44 AM, Dobbins, Roland wrote: >> Yes, it has. There're lots of issues with embedding IP addresses >> directly into apps and so forth which have nothing to do with NAT. > > Embedding into apps isn't the same as embedding into protocol packets. While > NAT and stateful firewalls do tend to break with embedded addresses that they > don't know to check for, it's still not a bad idea. > I was fixing to complain that the IPv6 designers didn't take the chance to > add the embedding to the Packet headers, when it occurs to me, they made the > headers nice and extensible. > > It also baffles me as to why applications such as skype dealing with NAT64 > can't use the compatibility addressing to start communicating with v4 hosts > from a v6 only NIC. I thought this was already a fixed problem not requiring > DNS to deal with. It's not like NAT46 (anyone actually publish such a hideous > protocol?), which requires really messy state tables bidirectionally for > everything and DNS rewrites. > > Jack
Compatibility addresses don't work on the wire. They're not supposed to. It's a huge problem if they do. Compatibility addresses allow you to write an IPv6 application, run it on a dual-stacked host and talk to the IPv4 and IPv6 remote systems as if all of them are IPv6 hosts. The IPv4 hosts appear to come from the IPv6 range ::ffff:ip:v4 which is often presented to the user as ::ffff:i.p.v.4 . Hope that clarifies things. Owen
