Brian, Yes, that is true, renumbering is a fact and we may be doing it eventually but hopefully not frequently. Needing to renumbering every time that a large enterprise changes internet provider (frequently, every 2 or 3 years perhaps) it is simply not practical today and possibly it will never be. Regards, as On 7 Aug 2012, at 05:20, Brian E Carpenter wrote: > 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 >>