Multi-commodity flow models are well known and have been widely used in the design of packet-switched networks. They have also been used as approximations in the design of circuit switched networks with reliability constraints. In this paper, we investigate the usefulness of multicommodity models both as routing models and as an integral part of design models conceived under the failure propagation strategy. First, we compare the performance measures calculated by the models with results produced by a real-time technique. Next, we study the performance of networks dimensioned with flow models and with classical adaptive models under failures of transmission facilities when a real-time routing technique is used. Results obtained using realistic data show that the multicommodity flow models compare favorably with exact dimensioning algorithms when failures are considered.