METHOD, ENTITY AND SYSTEM OF REALIZING NETWORK ADDRESS TRANSFER

摘要

A method of realizing network address translation (NAT) includes the following steps. An application function (AF) entity receives a message, and determines a signaling direction according to the message. The AF entity carries the signaling direction information in an access authorization request (AAR) message and sends the AAR message to a service-based policy decision function (SPDF) entity. The SPDF entity obtains a corresponding local domain address according to the signaling direction, and sends the obtained address to the AF entity. The AF entity sends the message according to the local domain address. An entity and a system of realizing NAT are also provided. By extending a message interacted between the AF entity and the SPDF entity and adding a field indicating a signaling direction, the SPDF entity is enabled to distinguish an uplink direction or a downlink direction of the message, for example, from an access side/a local core side to a core side/an opposite core side or from the core side/opposite core side to the access side/local core side, so as to realize an NAT control.