Noel Chiappa wrote: > > From: "Stephen Sprunk" <stephen@xxxxxxxxxx> > > > .. ULA-C/G leaks will not collide with each other. This means that, > > unlike RFC1918 which is _impossible_ for ISPs to route for multiple > > customers, ULA-C/G routes _can_ be routed publicly. Any prohibition > > on doing so by the IETF or RIRs can (and IMHO, will) be overridden by > > customers paying for those routes to be accepted. > > Which would argue that the only realistic way to make *absolutely certain* > that IPv6 "private" addresses truly *cannot* be used out in the 'main' > internetwork is to allocate the same ranges of addresses to multiple > parties. > Perhaps, but then we end up with all of the problems associated with ambiguous addresses, and we lose all of the advantage of IPv6. > Anything else is just PI with a few speedbumps, and a different label. > Maybe, maybe not. In practice, today, not every IPv4 address prefix is PI. Today, the length of your IPv4 prefix has some influence on whether your prefix gets advertised. There may not be an absolute boundary, but there is a barrier nonetheless. So I can certainly imagine that it would be harder to get ULA prefixes as widely advertised as PA prefixes. How much harder, I cannot say. So the speedbumps might be useful. But people wanting to absolutely forbid any ISP from advertising a ULA prefix will probably be disappointed. That doesn't bother me, because I don't think it's necessary to have that absolute prohibition in order for networks to push back on routing table size and routing complexity. Sooner or later, routing scalability will be a problem in IPv6. When that happens, each network will pick some means to decide which prefixes get advertised within its network and which get filtered. It's not rocket science to guess that networks will favor their own customers, the networks with which they have explicit agreements, and the networks from which their customers derive the most value. That probably puts most ULAs and PIs fairly far down in the preference list. _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf