Re: Lies, damned lies, and statistics that don't lie.
>"You can't invent a way for a machine that believes all addresses are 32 bits long to receive or send packets with longer addresses."
Backward compatible means that the new version will work with the old, not that the old will work with the new
Compatibility depends on context and the style and level of interoperability desired. However, the emphasis on end-to-end security in recent years has made things a lot more complex than they were in the early to mid 1990's when most traffic was unencrypted.
If you sanction the use of intermediate systems/gateways it is perfectly possible to get a client system to initiate communications with a system that uses longer addresses. However, expect some things to break, just as they break today with NAT.