Reliable data delivery is essential in the mobile ad hoc network (MANET) and the devices change their positions very frequently since they do not have any fixed infrastructure. In this paper, we have proposed multicast routing protocols for military communications. The military communications with MANET require data security. We using one of the most widely used algorithms Neighbor supporting Ad hoc Multicast routing protocol which is Mesh-based routing algorithm. Semi Markov process is used to develop the node behavior model for network survivability. In this work, reliable data delivery is obtained for the MANET by estimating the present performance of the network through isolating the forwarder node in Semi Markov process.