1. A computer-implemented method of determining a real time availability of a group of two or more network elements, the method comprising: determining a first real time availability value based upon both an estimated real time availability value for each network element in a first set of two or more network elements in the group of two or more network elements and cooperation relationships between the network elements in the first set of two or more network elements; and determining a second real time availability value based upon the first real time availability value, an estimated real time availability value for each network element in a second set of two or more network elements in the group of two or more network elements, wherein the second set of two or more network elements is different than the first set of two or more network elements, cooperation relationships between the network elements in the second set of two or more network elements and cooperation relationships between one or more network elements in the first set of two or more network elements and the second set of two or more network elements.