Martin, As far as the mass market goes, multiple prefixes and renumbering are a fact of life. See the MIF and HOMENET WGs for more. As far as enterprise networks go, renumbering is rather undesirable but sometimes inevitable, see 6RENUM. Regards Brian On 07/08/2012 08:46, Martin Rex wrote: > Brian E Carpenter wrote: > [ Charset UTF-8 unsupported, converting... ] >> On 06/08/2012 23:02, Martin Rex wrote: >>> Steven Bellovin wrote: >>>> Randy Bush wrote: >>>>> whatever the number of address bits, if it is fixed, we always run out. >>>>> memory addressing has been a cliff many times. ip addressing. ... >>>> Yup. To quote Fred Brooks on memory address space: "Every successful >>>> computer architecture eventually runs out of address space" -- and I heard >>>> him say that in 1973. >>> I'm wondering what resource shortage would have happened if IPv6 >>> had been massively adopted 10 years earlier, and whether we would have >>> seen the internet backbone routers suffer severely from the size >>> of the routing tables, if every single home customer (DSL subscriber) >>> would have required a provider-independent IPv6 network prefix rather >>> than a single, provider-dependent IPv4 IP Address. >> That was never a likely scenario (and still isn't). PA prefixes are still >> the norm for mass-market IP, regardless of version number. > > > IPv6 PA prefixes result in that awkward renumbering. > Avoiding the renumbering implies provider independent > network prefix. > > With IPv4, you would have typically keept your IPv4 network address > (the old class A, B & C from early 199x) even when changing network > providers. > > > To me, IPv6 PA prefixes look like a pretty useless feature > (from the customer perspective). Either you want an provider-independent > prefix to avoid the renumbering when changing providers, > or you want some level of privacy protection and therefore > a fully dynamic temporary DHCP-assigned IPv6 address > (same network prefix for 10000+ customers of the ISP) > and for use with NAT (again to avoid the renumbering). > > IPv6 renumbering creates huge complexity without value (for the customer). > > -Martin >