If the sole purpose of these addresses is for layer 3 connectivity as envisioned for LOCAL USE, then I would agree with Nir Arad that we do not have a problem. Stop reading here if that's your position.
If on the other hand, as Geoff states in his draft, and some people seem to be implying, that these addresses could be used as some sort of end point identifier outside of the routing system, then we do have a problem.
The reason this is an interesting problem is because these addresses have properties that would seem to align well with many people's idea of conceptually separate end point identifiers. In particular:
o Statistical v. Administrative uniqueness
-- see the NSRG draft o Easy processing as a fixed size and at a (mostly) fixed point in
the packet.o Below the transport that could be used to maintain connections.
o non-aggregatability
-- some would believe that since only a forward mapping is
necessary there is no need for aggregatability, and that indeed
one shouldn't allow these things to have properties of addresses
in order to avoid overloading of functions.A word of caution is in order. It is just that overloading, however, that we are doing in the context of local connectivity. And so for those who are considering this approach, you would be wise to consider a bit further as to the implications of that overloading. In particular, ipv6.arpa issues should be considered as well as any *forward* mapping from this address to globally routable IPv6 addresses.
The problems with doing this, however, are well stated in Geoff's draft. All of a sudden you are not simply interacting locally but more globally, and that means that for statistically "unique" values one should assume some collisions *will* occur (albeit rarely).
So in a peculiar sort of way, various efforts are converging towards very similar architectural properties but for somewhat different purposes.
Eliot
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