Hi Bob. > RFC3177, where the /48 recommendation was made, used the H ratio > analysis to explain why a /48 was acceptable. However the IETF did > not make any recommendation to the RIRs that the H ratio (current > version is now called HD ratio) should be used by the RIRs in their > allocation process nor what specific HD ratio be used. These choices > were made the RIRs when they developed their IPv6 allocation policies. > In my view the potential problems you describe have more to do with > the specific HD ratio the RIRs choose to use as opposed to the /48. > It's my understanding the HD-ratio value that the RIRs are now using > is much more conservative than before. This should, as I understand > it, avoid the overall problems you describe (e.g., cable modem, DLS, > etc.). Looking back at some old notes, I believe that changing the HD ratio thresholds gave us roughly one order of magnitude's worth of additional headroom. Moving the end site boundary from /48 to /56 gives us roughly two additional orders of magnitude savings. So, while one can certainly argue about just how much is "enough" (since projections 50-100 (or more!) years into the future are pretty iffy), I think that both changes were important to make. > While I agree that 64K subnets is a lot of subnets for a home user, > my reluctance to formally change the /48 recommendation is that it > will lead to much more restrictive allocation policies. Just like > the one that started this thread: IMO, this concern is overblown. And to be clear, I've heard this concern for years -- especially here in the IETF -- and it was one of the reasons why the 3177 recommendations were what they were. But having attended RIR meetings on and off for the last 5 years, and having talked with folk that go there, most of them very clearly understand that we have lots of IPv6 addresses and that the intention is that users get them. I do not hear serious talk about being restrictive in giving out subnets. What I do hear is that giving out /48 to everyone is simply profligately wasteful. And unjustified. And repeats the early mistakes of IPv4 where people didn't think about managing resources prudently. We shouldn't be surprised that a "one size fits all" approach (where home users get the same amount of space by default as an IBM or Microsoft) doesn't seem to make a lot of sense to some people. > > * /64 - Site needing only a single subnet. > > * /60 - Site with 2-3 subnets initially. > > * /56 - Site with 4-7 subnets initially. > > * /52 - Site with 8-15 subnets initially. > > * /48 - Site with 16+ subnets initially. > If this is what we would expect to get by changing the RFC3177 /48 > recommendation, then in my view is not a good idea. It should be noted that the policy proposal being quoted here was submitted even though RFC3177 is on the books. And that some RIRs have already adopted the change to /56. So, no, changing RFC 3177 isn't (IMO) going to open the door (any wider) to such proposals. At the same time the continuing existance of RFC 3177 is not going to stop RIRs from adopting policies that they think make sense. Leaving 3177 on the books as it currently stands, strikes me as a form of denial. It doesn't document existing practice, and at a minimum, we should acknowledge that. Thomas _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf