Dave Crocker <dhc2@xxxxxxxxxxxx> writes: > 4. The v6 stack would need to have a v4 mode, for use by v4 > applications -- applications that use v4 addresses. Um, sounds an awful lot like dual-stack to me. Hosts (that understand IPv6) also must be able to originate and receive either IPv4 packets or the bigger IPv6 ones. Sure, the details may be somewhat different, but fundamentally, we have dual stack, with IPv6 nodes needing to support IPv4 for backwards compatability. And in the network, routers have to understand both the original IPv4 format, plus the new IPv6 format. If there was a magic "trivial" transition/upgrade strategy, we would have done it years ago. Really. Thomas _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf