## 1 Introduction
The stopping condition of this procedure depends on the specific characteristics of the interactive procedure. It should be noted that, concerning interactive procedures, the emphasis on exact algorithms, of course, refers to the calculation phase only, that is, to the phase of calculation of efficient solutions. A second main purpose of our work is the presentation of an overview of selected papers considered as representative of different types of applications in telecommunication network routing models of multiobjective path problem formulations and of the associated resolution approaches. Note that the extremely rapid evolution of communication technologies, network architectures and provided services had an important impact on various aspects of the developed routing models. In fact, the advantage, in many cases, of explicit consideration of QoS metrics and economic-based metrics either as objectives to be optimized or as constraints has fostered an increasing interest in the development of multicriteria/multiobjective routing models. Note that routing methods deal with a number of issues other than path calculation since the functional technical entities that actually implement the establishment of routes, designated as routing protocols, have to execute several procedures concerning the management of various types of information/data following strict formats, contents and processing rules, dependent on the technical features of the network underlying technology(ies) and architecture. The possibility of implementing advanced routing methods of multicriteria nature, the advantages of which have been referred to above, is strongly related to the technical capabilities provided by modern network technologies and architectures. We highlight some technological evolutions in basic communication technologies which had an important impact on routing model developments. Firstly, Multiprotocol Label Switching (MPLS) was developed for packet-switched services (Internet-type services) and enables 'label-switched paths' (LSPs) to be established via label-switched routers, so that end-to-end traffic flows can be carried ensuring various QoS requirements. Figure 1: Interactive process (adapted from [4]). A further extension of MPLS specially developed for optical networks was Generalized MPLS (GMPLS) that provides control functionalities for advanced switching mechanisms, namely wavelength switching, time division multiplexing and fiber (port) switching. In essence, from a logical-functional point of view, this capability is equivalent to circuit-switching or circuit-routing, enabling routing principles perfectly analogous to those of classical multiservice digital telephone networks. Concerning physical transport technologies, Wavelength Division Multiplexing (WDM) and Dense WDM (DWDM) optical technologies enabled the use of tens of wavelengths on each fiber, so that extremely great information rates and enormous traffic carrying capabilities can be implemented associated with flexibility resulting from the possibility of wavelength conversion in the optical switches. Also, the Optical Transport Network (OTN) was designed as the base transport system for the Synchronous Digital Hierarchy (SDH) transmission system and was extended enabling the Internet Protocol (IP) and Ethernet protocols to be supported. It is capable of carrying very large bandwidths and allowing advanced mechanisms in terms of operations, administration, maintenance and provisioning at the level of wavelengths. Note that the interplay between various technologies in distinct functional layers of telecommunication networks enables various network architectures to be used such as IP/MPLS over WDM or IP-over-OTN-over-DWDM that enable the reduction of the needed router capacities and power consumptions and a more efficient utilization of bandwidth. A recent technological paradigm that is having a decisive impact in improving the working and management of current network structures is Software-Defined Networking (SDN).