1. A method of determining a routing of data between at least two network elements of a telecommunications network, which are interconnected or coupled via a transmission path, the method comprising: identifying, by at least one processor, a plurality of distinct transmission layers of a telecommunications model from which the transmission path is comprised, developing, by the at least one processor, a reachability matrix by identifying, by the at least one processor, a connection or a coupling between each transmission element in each layer to other transmission elements in the same or a different layer of the transmission path, for each connection or coupling as indicated by the reachability matrix, defining, by the at least one processor, a set of communications parameters which define a cost of communicating, by the at least one processor, data via the connection or the coupling, and allocating, by the at least one processor, a weighting value for communicating, by the at least one processor, data via the connection or the coupling, for all possible routes between the two network elements along the transmission path, via each of the layers, modeling, by the at least one processor, the effect of the connection or coupling for routing the data in accordance with the set of communications parameters for the connection or coupling and determining, by the at least one processor, a weighted result along each path, combining, by the at least one processor, the weighted results to determine a metric of performance for each of the possible routes, determining, by the at least one processor, an optimum route from the best evaluated parameters, and determining, by the at least one processor, one or more optimum transmission paths between the network elements as an optimization which comprises: mobile standards interfaces as one layer being optimized; at the same time as, optimizing, by the at least one processor, supporting transmission layers at a lower layer.