An expanding company is deploying leased lines between its main site and two remote sites. The bandwidth of the leased lines is 128kb/s each， terminated on different serial interfaces on the main router. These links are used for combined VOIP and data traffic. The network administrator has implemented a VOIP solution to reduce costs， and has therefore reserved sufficient bandwidth in a low latency queue on each interface for the VOIP traffic. Users now complain about bad voice quality although no drops are observed in the low latency queue. What action will likely fix this problem？（）