This paper presents and studies a reliable multicast protocol whose objective is to deliver a message to all intended destinations, despite possible crashes of the sender and other processes, and communication failures. The protocol enables QoS metrics such as absolute and relative latencies and the probability of reliable delivery, to be negotiated prior to service provisioning. Moreover, it adapts certain parameters dynamically in order to minimize the message traffic required to achieve the negotiated QoS metrics. The performance of the protocol is analyzed mathematically under simplifying assumptions. The accuracy of the approximations is evaluated by simulations.