Various embodiments of the present disclosure provide a method for traffic detection. The method which may be performed by a first network node includes receiving a message from a second network node. The method further includes determining packet flow description information for traffic detection according to the message. The packet flow description information may indicate a combination criterion for two or more packet flow descriptions, and/or a protocol matching criterion for a domain name in a packet flow description. According to the embodiments of the present disclosure, the packet flow description definition can be extended to support more accurate traffic detection.