The IP address depletion and scaling in routing are the two most compelling problems in IP Internet. The solution to is to place Network Address Translators (NAT) at the border of stub domain. Network Address Translation is the method by which IP addresses are mapped from one realm to another, in an attempt to provide transparent routing to hosts. Each NAT box has a small pool of globally unique IP domain are not globally unique; they are reused in other addresses that are dynamically assigned to IP flows going through NAT. The IP addresses inside the stub domains, thus solving the address depletion problem. The pool of IP addresses in NAT is from a subnet administered by the regional backbone, thus solving the scaling problem. The main advantage of NAT is that it can be installed without changes to routers or hosts.

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