Since the Internet must continue to support escalating growth due to increasing demand, it is clear that current routing architectures and operational practices must be updated. This document proposes an Internet Routing Overlay Network (IRON) architecture that supports sustainable growth while requiring no changes to end systems and no changes to the existing routing system. In addition to routing scaling, IRON further addresses other important issues including mobility management, mobile networks, multihoming, traffic engineering, NAT traversal and security. While business considerations are an important determining factor for widespread adoption, they are out of scope for this document.