[ppml] [address-policy-wg] Those pesky ULAs again

[Paul_Vixie at isc.org]

> You're always going to be looking at a sparse /64, you've got
> 18446744073709551616 addresses. But you need it if you want to do eui64.

sadly, eui64 is in the standard, and it would take a flag day to remove it.
so while i expect folks to switch from stateless address autoconfiguration
to DHCPv6 to get some auditing and to be able to set config knobs like name
server lists and so on, i believe that everybody will always use /64's for
LANs, since some embedded devices will always demand EUI64.  so there's no
way to get the address space back, and IPv6 is as leo said, effectively the
same size as a 72 bit address space.

(note well, there was an urban legend about the /64 boundary being present
in silicon on some switch or router, but in my own testing, every C and J
router i laid hands on was able to work with /96 or /120 netmasks on 
connected LAN interfaces, forward to them without using more CPU time than
a connected /64, receive routes, and advertise routes.  so at the moment,
"/64 is hardwired into router silicon" is just an urban legend to me.  if
you want to argue this point, plz provide session traces and rev levels.)