Performance of a threshold-based dynamic priority bandwidth allocation suitable for SDH/SONET-based Metro Area Optical Network is presented.The newly proposed scheme overcomes the inaccurate bandwidth allocation of threshold control and the complex computation of traditional priority algorithm and easy to realize in the system.We simulate the network transmit performance on a specific four-class priority system software test bed

the result shows that the TDPBA algorithm can assure the credible transmission for this kind of traffic maximum but at the cost of low QoS traffic

which is suitable for the application that with strict QoS requirements.