NAT provides routing transparency for hosts in disparate routing realms to communicate with each other. However, external agents such as Application Level Gateways (ALGs), Host-NAT-clients and Management applications need to interact with NAT and influence its operations. The document identifies the resources and other elements controlled by a NAT device, with specific focus on areas subject to influence from external agents. An Application Programming Interface (API) framework by which external agents could interact with NAT is presented. The intent of this document is to leverage the API specification as a base to identify requirements for the development of one or more protocols by which external agents could interact with NAT.