> "something useful" makes it subjective. some of us try to operate networks. useful is what customers pay us to do. > SLAAC, NPT66, ILNP are the biggest one that I can think of. slaac is real, used, and is useful in some environments that customers want. > Trivial to make SLAAC work with variable length prefixes of course. 64 for slaac is fine. for the rest, we went to cidr over a decade back, when folk scammed mo out of 8+8. randy