User data tracing method under network address translation (NAT) 444 deployment

The invention discloses a user data tracing method under network address translation (NAT) 444 deployment. With the method adopted, user identification (UID) can be matched according to IPs, and the method can be integrated into a real-time system with easiness. The method includes the following steps that: (I) the network address translation (NAT) 444 is deployed as a plurality of broadband remote access server (BRAS) insert cards and a small number of carrier-grade NAT (CGN) devices which are deployed in a centralized manner; (II) after fixed network address translation (NAT), a strategy that IPs and port blocks map pre-NAT IPs is adopted to perform translation; (III) in a cache, the IPs are adopted as key words to establish an account table, and segmented port block sequences are saved under IP nodes; and (IV) relevant information in an RADIUS is parsed through deep packet inspection (DPI) and is forwarded to an RM2000 module of load data access.