The increased use of virtual connections in packet switched networks, in particular over the Internet, using MPLS and GMPLS evolution has produced a significant amount of studies on traffic engineering protocols, especially with regard to the different ways to provide quality of service over connections. This article presents a model to characterize the reliability of these types of networks, in computing restricted route domain. With these elements, an application is proposed, to establish virtual connections with likely default reliability on MPLS / GMPLS networks.