A method and device partition physical transmission resources of a physical network. At first, a set of logical networks is established on top of the physical network. The logical networks comprise nodes and logical links extending between the nodes so as to form the logical networks. The logical links are used by routes. Next, the capacities of the logical links of the logical networks are determined such that the route blocking probability on each individual route in each one of the logical networks is less than or equal to a maximum allowed blocking probability for each individual route. This is realized by distributing, for each individual route, the route blocking evenly among the logical links used by the individual route. Finally, the physical transmission resources are allocated among the logical links of the logical networks according to the determination.