Method, device, and system for identifying traffic flow

The present disclosure provides a method, device, and system for identifying a traffic flow, the method comprising: according to a traffic flow identification policy, identifying a link identifier of a downlink traffic flow; transmitting to a downlink classifier the link identifier of the downlink traffic flow and description information of the downlink traffic flow so that the downlink classifier marks the downlink traffic flow according to the link identifier of the downlink traffic flow, and an uplink classifier and the downlink classifier are deployed in different network devices.