Legal monitoring method, communication system, router and monitoring gateway

The invention discloses a legal monitoring method which comprises the steps that: an edge tag switching router, as the monitoring access point, receives the monitored data and acquires the monitored tags of the monitored data; an equivalence class is transmitted according to the monitored tags and the destination address of the transmitted equivalence class is a monitoring gateway; the monitored data are sent to the monitoring gateway by a tag switching path corresponding to the transmitted equivalence class. The edge tag switching router in the invention, as the monitoring access point, allows not to encapsulate the monitored data in the IP message of the monitoring gateway which is the destination address after the router receives the monitored data, thereby simplifying the processing flow of the router. The invention also discloses a communication system, a router and a monitoring gateway.