[arin-ppml] What is a "host"?

[michael.dillon at bt.com]

> So, we really have to go back to basics if we want to do something
> sensible with v6 policy. There are two foundations for PI addresses:

Then count interfaces.
In IPv6, addresses are assigned to interfaces, and networks are composed
of subnets, which contain a bunch of interfaces. 

Nobody is going to walk around and count 1000 interfaces anyway. They are
going to estimate the number based on some other data such as switch ports
installed and VMs per server or VMs in the customer database.

> 2. You have a substantial enough system that renumbering to change
> your upstream provider is a more unreasonable burden than compelling
> everybody else to carry the route for your PI addresses.
> 
> Start from those foundations and work forward.

Given that we are talking about IPv6 renumbering, not IPv4 renumbering,
subnets still seems like a good measure. In IPv6, the subnets are unchanged
and you just change the network prefix handed out by SLAAC or DHCPv6.

--Michael Dillon