A new integrated scheme of differentiated services for the Internet is proposed in this paper. In this scheme, a service which combines both delay and drop priority is provided to applications with clear service differentiation. The integrated scheme is based on the dynamic buffer threshold (DBT) scheme. In the DBT scheme, the threshold is dynamically varied in run-time based on the packet loss behaviors. In the static buffer threshold (SBT) scheme, the variation of packet loss probabilities can be very large and there is no simple mathematical expression relating the threshold to the desired packet loss rate. These problems are overcome with the DBT scheme. In this paper, the performance model of the scheme is given using stochastic Petri nets and is analyzed by simulation.