A broadband network gateway (BNG) being connected to a terminal through at least one network including an aggregation network. The method includes: obtaining first transmission information and/or second transmission information, where the first transmission information includes information about transmission from the BNG to the aggregation network that is recorded by a first network edge node and information about transmission from the aggregation network to the terminal that is recorded by a second network edge node, and the second transmission information includes information about transmission from the terminal to the aggregation network that is recorded by a third network edge node and information about transmission from the aggregation network to the BNG that is recorded by a fourth network edge node; and detecting hop-by-hop network transmission quality between the BNG and the terminal based on the first transmission information and/or the second transmission information.