This paper presents a Path Bandwidth Management (PBM) model for large-scale networks that leads to an almost optimal PB allocation, under constraints posed by the installed bandwidth in the transmission links of the network. The PB allocation procedure is driven from a traffic demand matrix and consists of three phases. In the first phase, a suitable decomposition of the whole network takes place, where the large-scale network is split to a set of one-level sub-networks. In the second phase, the optimization algorithm developed for one-level telecommunication networks is applied to each sub-network in order to define the optimal PB allocation. The criterion for optimization is to minimize the worst Call Blocking Probability (CBP) of all switching pairs of the sub-network. In the third phase, composition of the sub-networks takes place in a successive way, which leads to the final PB allocation of the large-scale network. As the large-scale network is built up from optimized sub-networks, an almost optimal PB allocation is anticipated. For evaluation, the worst resultant CBP of the proposed scheme is compared with that obtained by the optimal PB allocation procedure in order to prove its optimality and efficiency. We choose a set of large-scale networks whose size is not very large so that we can apply the optimization algorithm developed for one-level telecom networks for defining its optimal bandwidth allocation. Extensive evaluation of the PBM model has showed that the worst resultant CBP is about 2% above the optimal value, which is a satisfactory result. The proposed PBM scheme is explained by means of an application example.