The basic idea of the plan is to allocate one or more blocks of Class C network numbers to each network service provider. Organizations using the network service provider for Internet connectivity are allocated bitmask-oriented subsets of the provider's address space as required.
It is also worthwhile to mention that once inter-domain protocols which support classless network destinations are widely deployed, the rules described by this plan generalize to permit arbitrary super/subnetting of the remaining class A and class B address space (the assumption being that classless inter-domain protocols will either allow for non-contiguous subnets to exist in the system or that all components of a sub-allocated class A/B will be contained within a single routing domain). This will allow this plan to continue to be used in the event that the class C space is exhausted before implementation of a long-term solution is deployed. This alternative is discussed further below in section 6.
Hierarchical sub-allocation of addresses in this manner implies that clients with addresses allocated out of a given service provider are, for routing purposes, part of that service provider and will be routed via its infrastructure. This implies that routing information about multi-homed organizations, i.e., organizations connected to more than one network service provider, will still need to be known by higher levels in the hierarchy.
The advantages of hierarchical assignment in this fashion are
For these reasons, and in the interest of providing a consistent procedure for obtaining Internet addresses, it is recommended that most, if not all, network numbers be distributed through service providers. These issues are discussed in much greater length in .