As I understand it, the primary issue with big-backbone-ISPs getting big chunks and startup ISPs not getting seperate chunks is that the small ISPs often grow big and want to do things like multihome. I know that's what has happened with scruz.net, where Matthew's speaking from, and several other ISPs I know of. As I understand it, people are generally reluctant to break up a large CIDR block to let some of it leave because it introduces at least 2 new routes globally... you end up with 3 routes, the block above the missing chunk, the block below the missing chunk, and the missing chunk from the new backbone provider. This is considered bad. It is not, however, completely necessary. Consider this as an option. Small ISPs signing up with their backbones agree to a form of semi-portability of addresses. The small ISP agrees that they will for (n years) maintain a direct IP link into backbone's network which can be used for getting packets to the block allocated from backbone's big CIDR blocks. This can be of arbitrarily slow speed if need be, or contractually obligated to be a 56k or greater, or T1 or whatever. Implimentation detail. In exchange, backbone agrees to artificially inflate the reachability cost in BGP advertisements to the large block and to allow small ISP to have any other backbone advertise the specific block at an easier to reach priority level. This allows the small ISP to dual home, or switch primary home, and sort of take their address with them (in that the new backbone can advertise the sub-block more attractively, thus making traffic most likely to flow that way). It also allows the origional backbone to not break up its block in its own announcements, and thus minimizes the number of total announcements made globally to no more than 2... one for the origional block, and a higher priority one for the sub-block which migrated. This would be no more advertisements than the case in which small ISP got its own space to start with and got it routed, and is actually easier on small ISP at the beginning. ISPs which have gone dual homed, connected to interchange points, etc. are likely to be able to justify /18 and up allocations directly from the NIC, and can slowly phase out their legacy blocks at that time. They can at their option renumber their internal hosts into their "own" space at that time, or not. They can let customers keep the origional space they were allocated, as routing for it is guaranteed one way or another. Or they can give customers the option to renumber into space the now midsized ISP has better, more direct control over. To avoid excessive headache, backbones should probably ONLY offer this sort of deal to bona-fide ISPs (of any size), not end-user customers. Comments? -george william herbert gherbert@crl.com