Multi-rate multicast is the most efficient way to support the future high speed, bandwidth varying and heterogeneous network. Past research into layered multicast protocols has mainly focused on the effectiveness of determining the maximal number of layers that can be subscribed to by each receiver, and the fairness issue with different sessions, especially for TCP. In this paper, we describe a new multi-rate multicast congestion control protocol called packet-pair bandwidth detection with session and layer changing manager (PSLM). PSLM can treat different sessions with different priorities and guarantees high transmission quality for important sessions. PSLM also addresses the layer stability issue to improve consistent quality requirement, as the support for stable network transmission. From our simulation results PSLM cannot only achieve the above two requirements but also keeps all the advantages from the original PLM protocol.