The author investigates the problem of dimensioning the transmission resources of a packet-switched communication network satisfying suitable reliability targets. The goal is a communication network providing a minimal transport capability in the presence of failures in network components. This goal is expressed in terms of availability functions to be satisfied by the reliability of communication links. The design procedure is based on the routing of each communication link on more than one transmission path, so that the availability of small shares of the communication link capacity can be increased. An analytic evaluation of the availability figures considered during the design phase is provided and the tools developed are used to compute an end-to-end reliability figure, which also takes into account the amount of user traffic.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>