The real time availability of a group of network elements is determined based upon both a real time availability value for each of the network elements and cooperation relationships between the network elements. The cooperation relationships reflect both the topological relationships between the network elements, i.e., how the network elements are connected, and the extent to which network elements interact with each other effectively. For relatively small groups of network elements, where the cooperation relationships are not overly complex, the real time availability is determined directly from the real time availability value for each of the network elements and cooperation relationships between the network elements. Decomposition and recombination are used to determine the real time availability of large groups of network elements based on specific formulas for basic network element topology models.