In this paper we are interested in building a general methodology for creating mechanisms that fully implement in Nash equilibria social utility maximising functions arising in various contexts in network economics where the constraints are linear or can be written equivalently in a linear form with the help of auxiliary variables. Such applications are among others, unicast, multi-rate multicast, economies with production, economies with private and public goods, local public goods, etc). The construction of the mechanism is done in a systematic way by considering the dual optimization problem. A novel allocation mapping ensures feasible allocations on and off equilibrium, while at the same time guarantees strong budget balance.