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This chapter gives an insight into some challenging combinatorial optimization problems that have to be tackled to deliver efficient and appropriate decision algorithms to manage future networks. The first part of the chapter is dedicated to variants of routing optimization problems in future IP networks, and the second part is dedicated to two optimization problems related to network virtualization and 5G network slicing, the virtual network embedding problem and the service function chaining problem. Each of these optimization problems is described along with the main challenges to overcome, and a recent and extensive related state of the art is given, so as to highlight the most recent and promising approaches to solve them.

In this paper, we address the Unsplittable Non-Additive Capacitated Network Design problem, a variant of the Capacitated Network Design problem where the flow of each commodity cannot be split, even between two facilities installed on the same link. We propose a compact formulation and an aggregated formulation for the problem. The latter requires additional inequalities from considering each individual arc-set. Instead of studying those particular polyhedra, we consider a much more general object, the unitary step monotonically increasing set function polyhedra, and identify some families of facets. The inequalities that are obtained by specializing those facets to the Bin Packing function are separated in a Branch-and-Cut for the problem. Several series of experiments are conducted on random and realistic instances to give an insight on the efficiency of the introduced valid inequalities. HighlightsWe give two ILP formulations for the UNACND problem.We introduce polyhedra associated with a general class of functions.We provide two classes of facets that are valid for all considered functions.We devise a Branch-and-Cut algorithm embedding both classes of inequalities.Our approach gives promising results and shows the efficiency of our inequalities.

We consider the Capacitated Multi-Layer Network Design with Unsplittable demands (CMLND-U) problem. Given a two-layer network and a set of traffic demands, this problem consists in installing minimum cost capacities on the upper layer so that each demand is routed along a unique “virtual” path (even using a unique capacity on each link) in this layer, and each installed capacity is in turn associated a “physical” path in the lower layer. This particular hierarchical and unsplittable requirement for routing arises in the design of optical networks, including optical OFDM based networks. In this paper, we give an ILP formulation to the CMLND-U problem and we take advantage of its sub-problems to provide a partial characterization of the CMLND-U polytope including several families of facets. Based on this polyhedral study, we develop a Branch-and-Cut algorithm for the problem and show its effectiveness though a set of experiments, conducted on SNDlib-derived instances and also on real instances.

We consider a mobile market driven by two Mobile Network Operators (MNOs) and a new competitor Mobile Virtual Network Operator (MVNO). The MNOs can partner with the entrant MVNO by leasing network resources; however, the MVNO can also rely on other technologies such as free WiFi access points. Moreover, in addition to its connectivity offer, the MVNO can also draw indirect revenues from services due to its brand. In that framework including many access technologies and several revenue sources, a possible partner MNO will then have to decide which wholesale price to charge the MVNO for its resources. This multi-actor context, added to the need to consider both wholesale and retail markets, represents a new challenge for the underlying decision-making process. In this paper, the optimal price setting is formulated as a multi-level optimization problem which enables us to derive closed-form expressions for the optimal MNOs wholesale prices and the optimal MVNO retail price. The price attractivity of the MVNO is also evaluated in terms of its indirect revenues and the proportion of resources leased from possible partner MNOs. Finally, through a game-theoretical approach, we characterize the scenario where both MNOs partner with the MVNO as the unique Nash equilibrium under appropriate conditions., Accepted in IFIP Networking 2018. Key words: Network Economics, Strategic Partnership, Multi-Level Optimization, Non-Cooperative Game Theory

We investigate a variant of the Multi-Layer Network Design problem where minimum cost capacities have to be installed upon a virtual layer in such a way that (i) a set of traffic demands can be routed AND (ii) each capacity (subband) is assigned a route in the physical layer. The traffic demands cannot be splitted along several paths (nor even several capacities installed on the same link), which makes the problem even more difficult. In this paper, we present new non-compact ILP formulations to model the problem and provide column generation procedures, based on different Dantzig-Wolfe decomposition schemes to solve it. More precisely, an arc-flow formulation is given for the problem and used to derive two different paths formulations: non-aggregated and aggregated. The former contains two families of path variables and requires a double column generation procedure to solve it, while the latter relies on a single path variable with a specific structure. These alternative modeling approaches induce two Branch-and-Price algorithms that allow to solve the problem efficiently for several classes of instances.

International audience; In this paper, we consider the Capacitated Network Design (CND) problem. We investigate the relationship between CND and the Bin-Packing problem. This is exploited for identifying new classes of valid inequalities for the CND problem and developing a branch-and-cut algorithm to solve it efficiently.