IPv6ユニキャストアドレス割り当て体系（リーフルーティングドメインの管理）

   As mentioned previously, the greatest degree of data abstraction
   comes at the lowest levels of the hierarchy. Providing each leaf
   routing domain (that is, site) with a contiguous block of addresses
   from its provider's address block results in the biggest single
   increase in abstraction. From outside the leaf routing domain, the
   set of all addresses reachable in the domain can then be represented
   by a single prefix.  Further, all destinations reachable within the
   provider's prefix can be represented by a single prefix.

   For example, consider a single campus which is a leaf routing domain
   which would currently require 4 different IPv6 prefixes.  Instead,
   they may be given a single prefix which provides the same number of
   destination addresses.  Further, since the prefix is a subset of the
   provider's prefix, they impose no additional burden on the higher
   levels of the routing hierarchy.

   There is a close relationship between hosts and routing domains.  The
   routing domain represents the only path between a host and the rest
   of the internetwork. It is reasonable that this relationship also
   extend to include a common IPv6 addressing space. Thus, the hosts
   within the leaf routing domain should take their IPv6 addresses from
   the prefix assigned to the leaf routing domain.