> If I assign 4M /48's of IPv6 (one to each cable modem on my > network), according to the HD-ratio I am justified to obtain > something around a /20 of IPv6 addresses. In other words, I am > justified in getting 268M /48's even though I am only > using 4M of > them. That would be enough for me to assign at least two for > every household in the US (not just the 19M on my network). > Anyhow, you can see where this might lead... Yes, towards a rethinking of whether the HD ratio is an appropriate way to measure the size of an ISP's second allocation. > If one does the math, giving every home user a /56 instead of > a /48 provides almost two orders of magnitude more headroom > in terms of address usage. And at what cost? Surely, everyone > will agree that giving a /56 to home sites is more than > enough space for the foresable future! That's enough for 256 > subnets per home site! That's an incredible amount of address space! And since it is very rare for a home site to change into a non-home site while under the same ownership/occupancy, the rule of /56 for home users maintains the same-size-for-all philosophy that was suggested with /48 blocks. A home user can move across town to another residence, hook up to another ISP and be reasonably guaranteed to get another /56. > That leads me to > doubt that the specific propoasl that was mentioned that > started this thread will actually get much traction within > ARIN, but that is not my problem. :-) Nevertheless, a lot of this controversy around IPv6 addressing is not very well informed and is often based on IPv4 architecture, not IPv6. There is a gap in education here, and due to the scramble to deal with the imminent runout of IPv4 addresses, people don't have time to get properly educated. This is a scenario in which informed guidelines from the IETF would have great value even if they cannot be prescriptive. > I find the fact that RFC 3177 has not been revised to reflect > the reality of today is a bit disapointing. Precisely! At one time the IETF put some effort into producing IPv6 educational material but that effort seems to have faded away. > And, FWIW, I was one of those that pushed for the changes. > As one who originally supported of the /48 recommendation in > RFC 3177, I think it was a mistake. Giving a /48 to every > home user by default is simply not managing the address space > prudently. Home users will do more than fine with a /56. I agree. What I don't agree about is the idea that /56's should go to small sites, i.e. that the ISP makes some judgement about how many subnets a business might need, and then decide whether or not to give them a /48 or a /56. Technically, the ARIN policy wording allows for this. --Michael Dillon _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf