Application layer multicast (ALM) is considered as an attractive approach for implementing wide area multicast services. In ALM, multicast functionality is implemented at the edge instead of the core network (routers). As opposed to network-layer multicast, application layer multicast requires no infrastructure support and can be easily deployed in the Internet. In this paper, we propose a new generic and scalable approach for optimizing application layer multicast in the context of Peer-to-Peer networks (structured and unstructured). This approach benefits from P2P properties and characteristics. In this contribution, we consider two approaches for multicast tree construction: a primitive” approach, and an optimized one based on a distributed algorithm. The proposed protocol inherits from main P2P attributes such as: scalability, fault tolerance.??Performance evaluation shows that results are globally satisfactory compared to the main existing application layer multicast protocols.