On Wed, 1 Oct 2008, Dunn, Jeffrey H. wrote:
1. It seems rather wasteful to assign 2^64 addresses to each link. This assignment corresponds to. 1.8x10^19 individual end systems. Even if this number of systems could be attached to a link, each speaker would only be able to transmit an octet every 4679 YEARS to the router on a gigabit link. I see no possible application for such an arrangement.
The point is not to able able to put 2^64 hosts on a link, it's being able to put *enough* nodes on the link, with *near-zero* address collision probability, so that you'll never need to renumber the link to have more address space if the address space was not sufficient after the number of connected hosts grow. An added bonus is an ability to design new protocols and mechanisms that are able to leverage those bits in the address with reasonable expectation of said technology being usable in the wild.
2. Since each VLAN is a link, i.e., a separate Ethernet broadcast domain, each VLAN on a physical interface must have its own prefix. As a result, to support the use of all possible VLAN identifiers (2^12 possibilities) each router interface with a VLAN module must be assigned at least a /52. For routers with multiple VLAN modules, 16 for example, this corresponds to the individual router requiring a /48. Although this is a worst case scenario, it illustrates the possibility of an enormous waste of address space.
You're not reserving a block of 2^12 IPv4 prefixes (or addresses in degenerate case) for each VLAN-capable router interface today, so I fail to see how this argument would apply to IPv6.
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