## 3 Applications to Communication Network Design
### Overview of Selected Papers  
Hereafter, we present an overview of selected papers considered as representative of different types of applications in telecom network routing in the scope of this work. As mentioned above, we will distinguish, in each subsection, three types of contributions: those corresponding to routing models that use as primary resolution procedure algorithm(s) specifically dedicated to the calculation of solutions to MOPPs, including heuristics and metaheuristics (these will be referred to in Section 3.2.1); routing models which use instrumentally, as auxiliary resolution procedures, MOPP-dedicated algorithm(s), including shortest path and \(k\)-shortest path algorithms (these will be referred to in Section 3.2.2); those models that involve explicitly, as the objective (but not necessarily the unique one) of the mathematical formulation, the calculation of paths that are solutions to MOPPs by recurring to Operations Research approaches which are not specifically dedicated to path problems, such as network flow, integer linear programming (ILP), mixed integer linear programming (MILP), non-linear programming (NLP) and other more general types of network optimization approaches that may be designated as 'network wide routing optimization approaches', in the sense defined in [145] and, in a multiobjective routing broad context, in [142]. This type of paper will be referred to in Section 3.2.3. Furthermore, throughout this overview we will give examples of contributions concerning different types of path solutions sought by the MOPP formulations referred to in each paper, namely single path node-to-node, path pair node-to-node and multipath node-to-node solutions. Note that each of these types of solutions corresponds to different types of routing models and may have different formulations that have to be contextualized in a particular network environment. Finally, we refer to a few, specific routing models, where multicriteria path problems are formulated through a multiattribute decision approach using an a priori specification of the system of preferences through an empirical utility function. These approaches were proposed for simplified heuristic multiobjective routing procedures in WSNs and ad-hoc WNs using hop-by-hop routing protocols where the node computation capability is very limited, and the information provided to a node is limited to metrics of the adjacent links (corresponding to arcs of the network graph representation). We would like to mention that in the late nineteen-nineties/early two-thousands, a new routing paradigm, designated as QoS routing, emerged as a result of the rapid technological evolutions, especially concerning IP-based services. This trend had to do with the need for the development of multiservice networks capable of dealing explicitly with different, heterogeneous QoS metrics. The associated routing models usually included multiple hard constraints or one objective function and several QoS-related constraints. As noted in [1], QoS routing models corresponding to constrained single objective path problem formulations may be considered as 'first tentative of multicriteria routing modelling' bearing in mind that a known approach to multicriteria optimization involves the transformation of the OFs into constraints, except one OF, which is to be optimized; in certain conditions, the calculated solution will be Pareto optimal for the associated MOPP which includes some of the former QoS constraint(s) as OFs [146]. This approach to the characterization of models, which should be considered as explicitly multicriteria, was also adopted by the authors in [3]. They propose a conceptual framework concerning the development of explicitly multi-criteria modeling approaches, for multicriteria QoS routing in IP-based networks and put forward a representative example of a routing model using achievement functions defined according to a reference point approach.