There is no bit length which allocations of /20's and larger won't quickly exhaust. It's not about the number of bits, it's about how we choose to use them.
Regards, Bill Herrin
True, but how many orgs do we expect to fall into that category? If the majority are getting /32, and only a handful are getting /24 or larger, can we assume that the average is going to be ~/28 ? If that is so, then out of the current /3, we can support over 30,000,000 entities. Actually, I would think the average is much closer to /32, since there are several orders of magnitude more orgs with /32 than /20 or smaller. Assuming /32 would be 500 million out of the /3. So somewhere between 30 and 500 million orgs. How many ISPs do we expect to be able to support? Also, consider that there are 7 more /3s that could be allocated in the future. As has been said, routing slots in the DFZ get to be problematic much sooner than address runout. Most current routers support ~1 million IPv6 routes. I think it would be reasonable to assume that that number could grow by an order of magnitude or 2, but I don't thin we'll see a billion or more routes in the lifetime of IPv6. Therefore, I don't see any reason to artificially inflate the routing table by conserving, and then making orgs come back for additional allocations. -Randy