Michael, Since you quote a work I co-authored, allow me respond: You state correctly that the current policy states that all IPv4 addresses allocated thorugh the Internet registry system according to the relevant policies at the time of allocation are unique regardless of their use. Policies are not natural laws, they can change over time. Usually they change whenever the environment or the requirements change. The operative change in this case is scarcity of unallocated IPv4 addresses which in turn will limit the growth of the Internet and the private IP networks alike. In this particluar case the operators of the Internet, *could* decide to change the uniqueness requirements such that IP addresses allocated via the present RIR system need only be unique as far as they are used on the Internet, for some definition of that. That would mean that IP addresses that were once guaranteed to be globally unique regardless of whether they were used on the Internet or private IP networks would no longer be guaranteed to be globally unique. Such a policy change would need to be designed and implemented carefully in order to enable all actors to make the necessary operational adjustments and to continue to guarantee registration and uniqueness within the newly defined domains. Such adjustments would almost certainly mean that operators of private or not widely announced IP networks would incur costs. On the other hand in the absence of such adjustments the operators of the Internet would incur costs because of the unavailability of IPv4 addresses. I am sure such trade-offs would be discussed vividly within BT. ;-) Responsible policy making will take into account these basic issues and adjust policies where necessary. In this particular case it is important to consider the likelihood of un-coordinated use of IPv4 addresses which are allocated but not widely used on the Internet and the associated operational costs as well as the consequential loss of credibility of the Internet registry system. Blindly insisting on the status-quo in the face of a changing environment is never helpful and often counter-productive. So I encourage those that favour "reclamation" propose concrete policies which take into account the issues which Michael raises. Making the right trade-offs is the art here. Most requirements are not as absolute as they may appear at first. One avenue to proceed could be to create multiple IPv4 address space registries ... boxes inside Pandora's ? Daniel