Many techniques have been proposed in the technical literature for repairing FPGAs when affected by permanent faults. Almost all of these works exploit the dynamic reconfiguration capabilities of an FPGA; a subset of the available resources is used as spares for replacing the faulty ones. Initially in this paper, a survey of these techniques is presented; subsequently, a framework is proposed for these techniques by which a fair comparison among them can be assessed and evaluated with respect to reliability. A reliability evaluation is provided for different repair strategies under the assumption that the area overhead is constant. Moreover, considerations about time to repair and feasibility of these techniques are provided. The ultimate goal of the paper is therefore to present the state-of-the-art repair techniques as applicable to FPGA and to establish their performance for reliability