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Recent studies on the practice of shaping user traffic by Internet service providers (ISPs) give new insights into the actual performance of broadband access networks at the network level. In this paper we investigate the effect of ISP traffic shaping on user-perceived performances. We use the application/session-level traffic models and performance measures for FTP, HTTP, and streaming video traffic as objective and quantifiable measures of user-perceived performances and study how the parameters of a token bucket filter (TBF) used in traffic shaping affect those measures. We first investigate the effect of the token generation rate and the token bucket size of a TBF on user-perceived performances with a single subscriber. Then we investigate with multiple subscribers their effect on the performances of multiple traffic flows interacting in a shared access network. The simulation results show that allowing users to send their traffic at a peak rate, much higher than the token generation rate, with a large token bucket size greatly improves user-perceived performances in both single- and multi-subscriber environments.