So if /64 is "subnet" rather than "node" then the practice of placing one and only one node per subnet is pretty wasteful.
In an IPv6 network, a /64 is the subnet prefix of a single broadcast domain, i.e. a single unbridged Ethernet segment. Within this subnet, there are many /128s which represent interfaces connected to the broadcast domain. These /128's are not "nodes" in the common sense of the term, i.e. they are not "boxes" or "devices". In some case, a device will only have a single interface connected to the broadcast domain, but ot could have more than one. If the device is a virtualization host, as is increasingly common, then it will have many virtual interfaces connected to the broadcast domain, each of which will have a /128 assigned to it.
And giving residential users a /48 will leave them with 80 bits for addressing.
No, it gives them 16 bits for subnetting. Everybody gets 64 bits for addressing because everybody (except oddballs and enevelope pushers) uses a /64 subnet size. Since 64 bits are more than anyone could ever possibly need for addressing and 16 bits is more than an end site could ever possibly need for subnetting, the /48 is an ideal allocation size. The whole point of IPv6 is to get rid of scarcity and parsimony in network architecture. If you aren't giving people more addresses than they need, then you aren't following the fundamental IPv6 model. Note that it is NOT wasteful to give people more addresses than they need. It allows things like the ULA random subnet selection algorithm to function with minimal probability of collision.
I know the reason for this is becasue they are allocated IP's based on number of possible subnets, rather than total number of available IP's, so it would be more fair to say they are allocated 65,536 subnets.
Yes! In IPv6 we do not allocate addresses, we allocate subnet bits. We don't count addresses either, we use an HD ratio based on counting subnets. People don't "get addresses" or "have addresses". They get subnets and have subnets.
So Acme DSL has been given a /32 from ARIN. Take someone like Comcast with ~12 million subscribers.
Can anybody say "scaling effects"? Comcast will never do things like a small ISP and vice versa.
It would take an IPv6 /24 to get 16.7 million /48's (2^24). With a net efficiency of 10% they are going to need to be allocated 120 million /48's. It would take a /21 to give them 2^(48-21) = ~134 million /48's.
Bad calculation. IPv6 usage efficiency is measured using the HD ratio and that is not what you are calculating. This is an especially important point for mid-size ISPs who go for a /32 allocation from ARIN. If you use up that /32 allocation and go back to ARIN to request another /32, you will *NOT* be able to bamboozle them with arbitrary figures like you are throwing around here. You *WILL* need to demonstrate that you meet the current HD ratio guidelines to justify another block.
I thought one of the goals of IPv6 was to assign ISP's huge blocks with low utilization so they don't have push a bunch of individual prefixes out to the worlds routing tables?
It would be good to seem some mid-sized ISPs presenting how they designed their internal addressing architecture taking into account the HD ratio needed to justify an additional allocation. This would include how they handle BGP route aggregation internally and externally. --Michael Dillon