Application programming interface and generalized network address translator for translation of transport-layer sessions

A method for facilitating message packet communication between a first application having an internal address valid in an internal address realm and one or more applications in an external address realm, said internal address realm having available to it a set of addresses valid for use in the external address realm, comprising:

• providing the internal address realm with a network address translation device having an address translator for translating addresses included in the headers of message packets incoming to and outgoing from the internal address realm in accordance with translation rules that resolve the incompatibility of the internal and external address realms;
• providing an address manager for establishing and storing the translation rules, said address manager having access to the set of available addresses valid for use in the external address realm;
• and
• providing a control channel communicating with the address manager for receiving from the first application a service request message for establishing in response to the first application's service request a translation rule specified by the first application,
• wherein the address manager transmits to the first application in response to the service request a first address valid for use in the external address realm and wherein the first application causes the first address to be transmitted to the external address realm in an SIP message.