sounds like a great idea for all of ipv6 allocation. what is the difference ula or pi/pa?
Here's my take. ULAs are not intended to be publically routed by ISPs. While some may attempt to get ISPs to route them, ISPs will have clear documentation saying they are not intended to be used that way, and they are free to filter them. And in fact they SHOULD be filtered. (I'd say MUST, but since that is not enforceable...) We have ULAs already. What is missing is centralized ULAs. I've had enough conversations with people that want to use ULAs - but simply aren't satisfied with probalistic uniqueness. They want something more meaningful, like a signed contract that that can pay some fee for and get some assurance that no one else is going to get that address. This sort of thing makes business people happy. People do worry about collisions and the impact that would have. ULAs are intended to be much more easy to obtain than PI space, because PI space is intended to be publically routed. PI space, on the other hand, is not useful if it is not publically routed (generally speaking). Poeple obtaining PI space are very much assuming it will be publically routed. ULA space is useful even if not publically routed (and is intended for uses that do not require public routability). E.g., it can be used to number infrastructure devices, with assurance those addresses will not need to change the way public addresses might. Is ULA space the same as PI? Only if you want to give everybody and their brother PI space and don't care about what that does to the routing tables. I don't believe we can (or should) do that. And keep in mind, in IPv6 devices can have multiple addresses simultaneously. So it is quite possible to have ULA-C addresses in addition to public addresses. So having ULA-C addresses does not imply that those addresses have to be used for communicating with off-site destinations. Thomas