On 28-sep-2006, at 14:35, JORDI PALET MARTINEZ wrote:
One possibility will be to allocate /48 but keep reserved the remaining /32. If the applicant justify that the /48 is getting filtered, then he may opt to justify to obtain the /32. Is this a possible compromise solution ?
History, both in IPv4 and IPv6, has shown that keeping space in reserve to accommodate future request doesn't work very well: people often end up announcing several blocks anyway. So let's not waste the space and make filtering harder by doing this. Also, since a /48 is an incredible amount of space to begin with, coming back for more should be rare in IPv6. The advantage of only giving out /48s with no unused space between them is that if, for instance, 12000 /48s are given out, that will be from a single /34 and allowing /48s from a /34 allows 16384 routes, while allowing /48s from a /20 (because for every /48 of 12000 a /32 is kept in reserve) allows 268 million routes, more than enough to overload any reasonable routing system in an attack.