> From what I have seen, those who think "local scope" is harmful, are > concerned about the ambuity of addresses, as Keith says here again. > They are NOT concerned about the fact that a given address may not be > reachable from some places, or may be reachable via different routes > from different places. There are multiple problems. One problem is simply that ambiguous addresses are a pain; to use them in any kind of referral (including DNS), you have to keep track of the context in which they're valid, and without a global scheme for naming those contexts there's no way to do that. This is a primary reason why we haven't been able to identify any good workarounds for NATs in IPv4 - the very use of ambiguous addresses by those NATs removes the one way we had of uniquely identifying not just hosts, but also networks or realms. (it's scary to think about, but we might actually be able to develop a reasonable NAT-tolerant architecture if we still had globally unique names for the realms) Another problem is that the existence of addresses that have limited reachability, _coupled with_ the expectation of multiple prefixes per host, immediately begs the problem of how the host is going to choose between those prefixes, especially if there's no obligation of the network to make something like longest prefix match work if the hosts are allowed to talk to one another. (it also begs the problem of how how apps can do referrals in that environment - yes, they can pass around all of the addresses but that's a pain). Both problems exist, and both are serious. Only the first problem is specific to SL (I don't consider v6 LL an issue). We don't pretend that getting rid of SL will address the second problem, but it helps because the absence of SL provides less incentive for networks to use addressing tricks as a means of filtering traffic. Keith