On Wed, Mar 24, 2010 at 12:35:38AM -0700, Owen DeLong wrote:
Only until v4 becomes more expensive (using whatever metric matters to you) than v6.
I have v4, it's not going to be anymore expensive than it is today for me... for new folks sure, but I've got mine.
If you start deploying IPv6, then, the cost of maintaining duplicate security policies (v4 and v6), duplicate host mappings, duplicate DNS, duplicate configurations on all your routers, etc. does eventually add up, as does the need for even more TCAM.
bingo. to move -from- a single stack system (IPv4) to a dual stack system (v4 & v6) is horrifically expensive. and to justify it based on the eventual cost savings of returning to a single-stack system "someday" might be problematic. one will pay those costs -if- there is an acceptable cost/benefit tradeoff.
These costs may be trivial in small environments, but, for major enterprises and large backbones, these costs will become significant.
An additional not-yet recognized cost of IPv4 will come to light as the various transfer policies start super-fragmenting the address space and our TCAMs begin exploding with new IPv4 routes. Likely there will be scenarios where ISPs need a /16 but they can only find 240 non-aggregable /24s. They'll snap them up and bam... 240 new IPv4 routes.
i will note in passing that an ipv6 /32 is the functional equivalent of an ipv4 /32... with the community accepting /48's, we will exceed the potential route injection capability of ipv4. we will potentially have more ipv6 routes than we could have ipv4... simply because we can't get any finer grained in IPv4 than a /32... while we can in IPv6.
The ARIN transfer policies has some safeguards against this, but, most of the RIRs passed transfer policies without these safeguards.
last I checked ARIN transfer policies didn't really talk to routing deaggregation much. in part because ARIN has (to date) almost no leverage on who announces what.
Owen