Extending the IP internet through address reuse

The two most compelling problems facing the IP Internet are IP address depletion and scaling in routing. This paper discusses the characteristics of one of the proposed solutions---address reuse. The solution is to place Network Address Translators (Nat) at the borders of stub domains. Each Nat box has a small pool of globally unique IP addresses that are dynamically assigned to IP flows going through Nat. The dynamic assignment is coordinated with Domain Name Server operation. The IP addresses inside the stub domain are not globally unique---they are reused in other 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 any existing systems, although FTP will fail in some but not all cases. This paper presents a preliminary design for Nat, and discusses its pros and cons.