In this article, Guarantee of Service (GoS) is defined as a proposal to improve the integration of Mission Critical Networking (MCN) services in the Internet, analyzing the congestion impact on those privileged flows with high requirements of trust and delay. Multiprotocol Label Switching (MPLS) is a technology that offers flow differentiation and QoS in the Internet. Therefore, in order to improve network
performance in case of congested domains, GoS is proposed as a technique that allows the local recovering of lost packets of MPLS privileged flows. To fulfill the GoS requirements for integration of MCN in MPLS, a minimum set of extensions to RSVP-TE has been proposed to provide GoS capable routes. Moreover, we have carried out an analytical study of GoS scalability and a performance improvement analysis by means of simulations.