In mobile ad hoc network, there are many multicast protocols that apply mesh topology and on-demand concepts such as On-Demand Multicast Routing Protocol (ODMRP). ODMRP uses periodic broadcasting transmission of control packets (e.g. Join Requests control packets) to build and maintain mesh topology. But, it suffers from higher control overhead as the network size and the number of sources increases. DCMP's designers solve the scalability problem of ODMRP by reducing control overhead. DCMP reduces control overhead by applying a new style of centralization (core) approach. It allows to each passive source to multicast its data packets only via its associated individual core source after constructing passive-core link. But, DCMP suffers from ease breakage of each passive-core link as a result of applying high mobility speeds. In this paper, we modify DCMP protocol by implementing a new algorithm called "SCPL" inline DCMP. Main target of SCPL is to make passive-core link more stable and hence to allow any source to enter passive status for a long time if it wants. Each passive source is prevented from broadcasting Join Request control packets which reduces control overhead and then improves scalability