An all digital TDMA dynamic channel allocated satellite communications system and method provides a satellite communications network between geographically separated nodes. The topology of the network is controlled by an on-line master node in accordance with user demands and operator commands received from the nodes in the network. A frame communication format is employed where each node in the system is allocated a burst within each frame. The length of the bursts is controlled by the on-line master node to provide the communications channels in the network. Control information to and from the on-line master node is conveyed in the network via the satellite link in selected frame bursts. In this way, the on-line master node dynamically controls the topology of the satellite communications network.