David Conrad wrote:
You also can't scale PA when it ends. You only can allocate new one.
The difference, of course, is that PA (by definition) can be aggregated into a single announcement, thereby reducing the amount of information sloshing around the routing system. It is true that if an ISP runs out of PA prefixes to assign to their customers that they'll need to get another one and that additional prefix will need to be PI, but that is a single prefix that aggregates all the customers numbered out of that prefix. This is Routing Scalability 101.
Please, see the difference of just customers (who don't know anything about PI vs PA at all, using their ADSL connection and be happy) and those who need own routing policy and own IP space. You can't aggregate second one into single prefix by definition. Again, I don't even think about "portable IPs to any customer" at this stage of Internet evolution. May be a bit later? But not now. -- WBR, Max Tulyev (MT6561-RIPE, 2:463/253@FIDO)