The goal of IP mobility support is to provide the means by which applications on distinct computers are able to communicate when one or both computers have changed their physical network location. Mobile IP (MIP) tries to provide such support with a solution at the network layer.To date, MIP deployment is insignificant and this is likely to remain so, unless there is a breakthrough. In contrast, Network Address Translation (NAT) is a network technology that is widely deployed. The Reverse Address Translation protocol (RAT) attempts to deploy mobility support by riding on this popular, proven technology.Registration of the mobile node in RAT is done through existing applications (e.g. browsers) and traffic delivery is by address translation rather than tunneling; thus, the mobile node does not require operating system support nor RAT-specific modifications. RAT separates the registration and forwarding functions of the home agent, and does not support handover of connections.RAT is designed to interoperate with MIP, since one of its goals is to act as a bootstrap for encouraging MIP deployment.