In the context of telecommunication virtualized networks, a Service Function Chain (SFC) is an origin-destination traffic demand having some specific service requirements. These service requirements are expressed as an ordered set of Network Functions (NF) that must be visited -- on the given required order -- along the SFCs origin-destination route. The virtualization of NFs allows the execution on demand of a network function within a virtual server, dissociating it from any dedicated hardware. While the virtualization of network functions allows more flexibility and cost reductions for the service deployment, it also represents a substantial challenge for infrastructure providers since the failure of a single node where a network function is hosted causes the crash of the whole SFC. In order to ensure strict Service Level Agreements (SLAs), a backup plan is required in case some network nodes fail. In other words, the service provider must ensure for each SFC that a set of alternative paths is ready to route it whenever its nominal path is unavailable. Notice that an alternative path can only route a given SFC if the network functions it requires are already placed along the considered the path. Since the placement of network functions incurs extra costs, a relevant combinatorial problem is to choose where to place such functions in order to minimize the costs while ensuring high standards of resilience.