Some background and history. The IETF gave it's view on where the boundary for IPv6 blocks to end sites should be (i.e., the /48 recommendation) in RFC 3177 back in the 2000-2001 time frame. At that time, there were plenty of folk in the IETF that thought the IETF could/should set address policy, notwithstanding fact that the RIRs were doing that for IPv4. RFC 3177 was a way for the IETF to make a recommendation to the RIRs, without stepping on RIR toes (too much). Note that it is only a recommendation, and the RFC is informational. The fact is, the /48 boundary is _NOT_ architectural, and saying it is doesn't make it so. I challenge anyone to find a standards track document that relies on /48 being part of the architecture. (And you might want to have a look at http://tools.ietf.org/id/draft-narten-ipv6-3177bis-48boundary-02.txt as it does mention a couple of related things.) What the appropriate size of an assignment for an end site should be is really more of an operational issue than architectural one. If a site gets too little, and needs to get more later (maybe at the cost of renumbering) that is an operational issue. And the idea that we can give out "enough" address space to a site so that it doesn't have to renumber (ever) is pretty silly. After all, most end sites will need to renumber when they switch providers. Surely, we hope/expect a large number of such provider switches to take place over a 5 or 10 year period anyway? The RIRs adopted the "/48 to everyone" in its initial stab at IPv6 policy back in 2002. Even at that time, there was much screaming and gnashing of teeth from the operator community saying "wasteful", "excessive", "really stupid", etc. So, even though all the RIRs adopted the policy anyway, the unhappiness with /48 (as a general recommendation) didn't go away, and was repeated often at subsequent RIR meetings... Then, 2-3 years ago, RIPE made some really really big IPv6 allocations to a few ISPs. This raised eyebrows, because it raised the question that if so much space could legitimately be given out (and it was much much more than the operators would have been given for the same number of IPv4 customers), it was conceivable to imagine scenarios in 50-100 years where the IPv6 free pool was signficantly used. As one Cable Modem operator explained it to me: 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). Now if all the cable providers (e.g., Comcast, Cox, Adelphia, Cablevision, Time-Warner, etc.) did the same for their networks; and each of the DSL companies made a similar move (SBC, Verizon, Quest, etc.); perhaps we could easily see the broadband market in the US alone obtaining some 16 /20's of IPv6 or a total of /16. There are only 8192 of those available in the current global unicast space of 2001::/3. Anyhow, you can see where this might lead... This led to a bunch of discussions and policy proposals in the RIRs, culminating with the adoption in ARIN, RIPE & APNIC of recommendations that adjusted the HD ratio thresholds and moved away from "/48 for everyone", making it an ISP (or LIR in RIR terminology) choice. The community feedback was that LIRs were smart enough to make reasonable assignments based on actual customer need. 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! (I have a really hard time reconciling the previous paragraph with the subject of this thread.) It is worth noting that there are no _firm_ recomendations in the current RIR policies (in the sense of saying you must give home users a /56) , because in discussions at ARIN and APNIC in particular, there was pushback from the operations folk on being to prescriptive. They argued that they are in the best position to decide reasonable assignment sizes and wouldn't support more rigid guidelines. 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. :-) Folk should note that a policy proposal submitted to an RIR is not unlike an individual submission "submitted" to the IETF. Best to treat it as such. YMMV. I find the fact that RFC 3177 has not been revised to reflect the reality of today is a bit disapointing. Even in some of the messages of this thread, I sense denial about the proper/actual role the IETF plays in setting address policy. I see some of the same people arguing here that /48 should not be changed, despite having made the same arguments on RIR lists and having lost... There is water under the bridge here folk... The reality is that "/48 for everyone" has been overcome by events. If you don't like that, take it to the RIRs. 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. Thomas _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf