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  • A story of diameter, radius, and (almost) Helly property
    Networks (IF 2.602) Pub Date : 2020-10-16
    Guillaume Ducoffe; Feodor F. Dragan

    We present new algorithmic results for the class of Helly graphs, that is, for the discrete analogues of hyperconvex metric spaces. Specifically, an undirected unweighted graph is Helly if every family of pairwise intersecting balls has a nonempty common intersection. It is known that every graph isometrically embeds into a Helly graph that makes of the latter an important class of graphs in metric

  • Telecommunications network design: Technology impacts and future directions
    Networks (IF 2.602) Pub Date : 2020-10-16
    Richard T. Wong

    During the past 50 years telecommunication network technology has raced ahead powered by exponential advances in computer chip and fiber optic technology. The introduction of packet‐switched networks and the Internet has increased network traffic demands exponentially and has nurtured a variety of new telecommunication services (e.g., email, web‐surfing, social media, streaming services, e‐commerce

  • In search of network resilience: An optimization‐based view
    Networks (IF 2.602) Pub Date : 2020-10-08
    Thomas C. Sharkey; Sarah G. Nurre Pinkley; Daniel A. Eisenberg; David L. Alderson

    Fifty years of research in Networks coincides with 50 years of advances in resilience theory and applications. The purpose of this review is to identify how these two technical communities influenced each other in the past and can bolster each other in the future. Advances in resilience theory show that there are at least four ways networks demonstrate resilience: robustness, rebound, extensibility

  • Recent challenges in Routing and Inventory Routing: E‐commerce and last‐mile delivery
    Networks (IF 2.602) Pub Date : 2020-10-06
    Claudia Archetti; Luca Bertazzi

    In the e‐commerce era, vendors have to satisfy a large number of on‐line orders, mainly from private customers, with low weight and volume, reduced delivery time, and overlap of customers' time windows. Production is made available all day long. New strategies and new technologies are emerging for deliveries. The processing time of the orders is reduced. These new features generate interesting challenges

  • On approximate data reduction for the Rural Postman Problem: Theory and experiments
    Networks (IF 2.602) Pub Date : 2020-10-06
    René van Bevern; Till Fluschnik; Oxana Yu. Tsidulko

    Given an undirected graph with edge weights and a subset R of its edges, the Rural Postman Problem (RPP) is to find a closed walk of minimum total weight containing all edges of R. We prove that RPP is WK[1]‐complete parameterized by the number and weight d of edges traversed additionally to the required ones. Thus RPP instances cannot be polynomial‐time compressed to instances of size polynomial in

  • A polynomial algorithm for minimizing travel time in consistent time‐dependent networks with waits
    Networks (IF 2.602) Pub Date : 2020-09-28
    Jérémy Omer; Michael Poss

    We consider a time‐dependent shortest path problem with possible waiting at some nodes of the graph and a global bound W on the total waiting time. The goal is to minimize the time traveled along the edges of the path, not including the waiting time. We prove that the problem can be solved in polynomial time when the travel time functions are piecewise linear and continuous. The algorithm relies on

  • Secure and efficient routing on nodes, edges, and arcs of simple‐graphs and of multi‐graphs
    Networks (IF 2.602) Pub Date : 2020-09-25
    Georg E. A. Fröhlich; Karl F. Doerner; Margaretha Gansterer

    Many security companies offer patrolling services, such that guards inspect facilities or streets on a regular basis. Patrolling routes should be cost efficient, but the inspection patterns should not be predictable for offenders. We introduce this setting as a multi‐objective periodic mixed capacitated general routing problem with objectives being cost minimization and route inconsistency maximization

  • Efficient algorithms for finding 2‐medians of a tree
    Networks (IF 2.602) Pub Date : 2020-09-21
    Aissa Oudjit; Matthias F. Stallmann

    The p‐median problem for networks is NP‐hard, but polynomial time algorithms exist for trees (n is the number of nodes): O(pn2) by Tamir, and O(n lgp + 2 n) by Benkoczi and Bhattacharya. Goldman gave an O(n) algorithm for the 1‐median problem on trees. Mirchandani and Oudjit proved localization properties for 2‐medians on trees; these were later used to obtain an O(nlg n) bound, and, in special cases

  • Parameter estimation in a 3‐parameter p‐star random graph model
    Networks (IF 2.602) Pub Date : 2020-09-18
    Pietro Lenarda; Giorgio Gnecco; Massimo Riccaboni

    An important issue in social network analysis refers to the development of algorithms for estimating parameters of a social network model, using data available from the network itself. This entails solving an optimization problem. In the paper, we propose a new method for parameter estimation in a specific social network model, namely, the so‐called p‐star random graph model with three parameters.

  • Effects of update frequencies in a dynamic capacitated arc routing problem
    Networks (IF 2.602) Pub Date : 2020-09-16
    Wasin Padungwech; Jonathan Thompson; Rhyd Lewis

    The capacitated arc routing problem (CARP) concerns a minimum‐cost set of routes for vehicles that provide service on edges in a given graph while ensuring that the total demand in each route does not exceed the vehicle's capacity. This paper concerns a dynamic variant of the CARP. In particular, it focuses on a problem in which new tasks appear over time. We find that simply increasing the number

  • Weighted target set selection on trees and cycles
    Networks (IF 2.602) Pub Date : 2020-09-10
    S. Raghavan; Rui Zhang

    There is significant interest in understanding the dynamics of influence diffusion on a social network. The weighted target set selection (WTSS) problem is a fundamental viral marketing problem arising on social networks. In this problem, the goal is to select a set of influential nodes to target (e.g., for promoting a new product) that can influence the rest of the network. The WTSS problem is APX‐hard

  • Minimum color‐degree perfect b‐matchings
    Networks (IF 2.602) Pub Date : 2020-09-10
    Mariia Anapolska; Christina Büsing; Martin Comis; Tabea Krabs

    The minimum color‐degree perfect b‐matching problem (Col‐BM) is a new extension of the perfect b‐matching problem to edge‐colored graphs. The objective of Col‐BM is to minimize the maximum number of differently colored edges in a perfect b‐matching that are incident to the same node. We show that Col‐BM is ‐hard on bipartite graphs by a reduction from (3,B2)‐Sat, and conclude that there exists no

  • The mixed capacitated general routing problem with time‐dependent demands
    Networks (IF 2.602) Pub Date : 2020-09-09
    Chahid Ahabchane; André Langevin; Martin Trépanier

    The mixed capacitated general routing problem (MCGRP) is defined over a mixed graph, for which some nodes, arcs, and edges must be serviced. The problem consists of determining a set of routes of minimum cost that satisfy the demand. Some problems like salt spreading have a time‐dependent demand which was ignored in the previous studies. This variation of demand is due to the weather or traffic conditions

  • Applications and efficient algorithms for integer programming problems on monotone constraints
    Networks (IF 2.602) Pub Date : 2020-09-09
    Dorit S. Hochbaum

    We present here classes of integer programming problems that are solvable efficiently and with combinatorial flow algorithms. The problems are characterized by constraints that have either at most two variables per inequality that appear with opposite sign coefficients, or have in addition a third variable that appears only in one constraint. Such integer programs, referred to here as monotone IP2

  • Large‐scale zone‐based evacuation planning—Part I: Models and algorithms
    Networks (IF 2.602) Pub Date : 2020-09-07
    Mohd. Hafiz Hasan; Pascal Van Hentenryck

    In zone‐based evacuation planning, the region to evacuate is divided into zones, and each zone must be assigned a path to safety and departure times along the path. Zone‐based evacuations are highly desirable in practice because they allow emergency services to communicate evacuation orders and to control the evacuation more precisely. Zone‐based evacuations may also be combined with contraflows (to

  • Future directions in drone routing research
    Networks (IF 2.602) Pub Date : 2020-09-07
    Stefan Poikonen; James F. Campbell

    Optimization of routing problems using drones (unmanned aerial vehicles or UAVs) has become an important area of academic research. The purpose of this article is to look to the future and help stimulate drone routing research in directions we hope will prove interesting and fruitful. We discuss opportunities for better modeling of (1) drone capabilities for both existing drones and those likely to

  • Large‐scale zone‐based evacuation planning, Part II: Macroscopic and microscopic evaluations
    Networks (IF 2.602) Pub Date : 2020-09-07
    Mohd. Hafiz Hasan; Pascal Van Hentenryck

    A companion paper introduces models and algorithms for large‐scale zone‐based evacuation planning in which each evacuation zone is assigned a path to safety and a departure time. It also shows how to combine zone‐based evacuations with contraflows and impose additional path‐convergence and nonpreemptive constraints. This paper evaluates these algorithms on a real, large‐scale case study, both from

  • A branch‐and‐dive heuristic for single vehicle snow removal
    Networks (IF 2.602) Pub Date : 2020-09-07
    Roghayeh Hajizadeh; Kaj Holmberg

    This paper deals with planning of a tour for a vehicle to clear a certain set of streets in a city of snow. Our previous results on the problem contain a heuristic based on reformulation to an asymmetric traveling salesman problem (ATSP) which yields feasible solutions and upper bounds, and a relaxation of a MIP model for obtaining lower bounds. The goal now is to try to improve the solutions and bounds

  • The parking warden tour problem
    Networks (IF 2.602) Pub Date : 2020-09-03
    Maurizio Bruglieri

    In this work we introduce the parking warden tour problem (PWTP), a new arc routing problem arising in irregular parking detection to model the maximization of the fines collected by a team of parking wardens. The peculiarity of the PWTP is that the arc revenue depends on the time elapsed from the previous inspection of a warden, since the revenue on a road link slumps to zero if a warden has just

  • Most reliable two‐terminal graphs with node failures
    Networks (IF 2.602) Pub Date : 2020-07-26
    Isaac Brown; Christina Graves; Brendan Miller; Tyler Russell

    A two‐terminal graph is an undirected graph with two specified target vertices. If each nontarget vertex of a two‐terminal graph fails independently with the same fixed probability (and edges and target vertices are perfectly reliable), the two‐terminal node reliability is the probability that the target vertices are in the same connected component in the induced subgraph of all operational nodes.

  • On undirected two‐commodity integral flow, disjoint paths and strict terminal connection problems
    Networks (IF 2.602) Pub Date : 2020-08-30
    Alexsander A. de Melo; Celina M. H. de Figueiredo; Uéverton dos Santos Souza

    Even, Itai, and Shamir (1976) proved simple two‐commodity integral flow is NP‐complete both in the directed and undirected cases. In particular, the directed case was shown to be NP‐complete even if one demand is unitary, which was improved by Fortune, Hopcroft and Wyllie (1980) who proved the problem is still NP‐complete if both demands are unitary. The undirected case, on the other hand, was proved

  • Plowing with precedence in polynomial time
    Networks (IF 2.602) Pub Date : 2020-08-28
    Rodrigo A. Castro Campos; Cynthia A. Rodríguez Villalobos; Francisco Javier Zaragoza Martínez

    The plowing with precedence problem is a variant of the windy postman problem, where a plow is required to clean streets after a heavy snowfall with traversing costs depending on the direction of traversal as well as whether a street has been previously plowed or not. We prove that this problem can be solved in polynomial time under natural cost structures. We also propose heuristics for this problem

  • Tangle bases: Revisited
    Networks (IF 2.602) Pub Date : 2020-08-21
    Illya V. Hicks; Boris Brimkov

    The concept of branch decomposition was first introduced by Robertson and Seymour in their proof of the Graph Minors Theorem, and can be seen as a measure of the global connectivity of a graph. Since then, branch decomposition and branchwidth have been used for computationally solving combinatorial optimization problems modeled on graphs and matroids. General branchwidth is the extension of branchwidth

  • The firebreak problem
    Networks (IF 2.602) Pub Date : 2020-08-21
    Kathleen D. Barnetson; Andrea C. Burgess; Jessica Enright; Jared Howell; David A. Pike; Brady Ryan

    Suppose we have a network that is represented by a graph G. Potentially a fire (or other type of contagion) might erupt at some vertex of G. We are able to respond to this outbreak by establishing a firebreak at k other vertices of G, so that the fire cannot pass through these fortified vertices. The question that now arises is which k vertices will result in the greatest number of vertices being saved

  • Network reliability: Heading out on the highway
    Networks (IF 2.602) Pub Date : 2020-08-14
    Jason I. Brown; Charles J. Colbourn; Danielle Cox; Christina Graves; Lucas Mol

    A variety of probabilistic notions of network reliability of graphs and digraphs have been proposed and studied since the early 1950s. Although grounded in the engineering and logistics of network design and analysis, the research also spans pure and applied mathematics, with connections to areas as diverse as combinatorics and graph theory, combinatorial enumeration, optimization, probability theory

  • Fixed interval scheduling with third‐party machines
    Networks (IF 2.602) Pub Date : 2020-08-08
    Ilia Fridman; Mikhail Y. Kovalyov; Erwin Pesch; Andrew Ryzhikov

    We study a problem of scheduling n jobs on machines of two types: in‐house machines and third‐party machines. Scheduling on in‐house machines incurs no additional costs, while using third‐party machines implies costs depending on their number and the time of usage. Each job has a fixed time interval for being processed which can be divided and allocated among several machines, as long as there is only

  • An exact bidirectional pulse algorithm for the constrained shortest path
    Networks (IF 2.602) Pub Date : 2020-06-21
    Nicolás Cabrera; Andrés L. Medaglia; Leonardo Lozano; Daniel Duque

    A constrained shortest path is a minimum‐cost sequence of arcs on a directed network that satisfies knapsack‐type constraints on the resource consumption over the arcs. We propose an exact method based on a recursive depth‐first search procedure known as the pulse algorithm (PA). One of the key contributions of the proposal lies in a bidirectional search strategy leveraged on parallelism. In addition

  • Integrating production scheduling and transportation procurement through combinatorial auctions
    Networks (IF 2.602) Pub Date : 2020-07-14
    Chefi Triki; Sujan Piya; Liang‐Liang Fu

    This study uses the winner determination problem (WDP) to integrate auction transportation procurement with decisions related to production scheduling. The basic problem arises when a manufacturer has to clear a combinatorial auction to decide whether to cover transportation needs by using the in‐house fleet or to procure transportation through auction. Thus, the manufacturer should include an additional

  • A branch‐and‐cut approach and alternative formulations for the traveling salesman problem with drone
    Networks (IF 2.602) Pub Date : 2020-06-22
    Daniel Schermer; Mahdi Moeini; Oliver Wendt

    In this paper, we are interested in studying the traveling salesman problem with drone (TSP‐D). Given a set of customers and a truck that is equipped with a single drone, the TSP‐D asks that all customers are served exactly once and minimal delivery time is achieved. We provide two compact mixed integer linear programming formulations that can be used to address instances with up to 10 customer within

  • Routing electric vehicles with a single recharge per route
    Networks (IF 2.602) Pub Date : 2020-06-25
    Maximilian Löffler; Guy Desaulniers; Stefan Irnich; Michael Schneider

    Driven by environmental considerations, regulations on vehicle emissions, and the offer of major subsidies, electric commercial vehicles (ECVs) are receiving ever stronger attention in logistics companies. Route planning for ECV fleets requires consideration of the special characteristics of ECVs, like limited driving range and the potential need to recharge en route at dedicated recharging stations

  • Avoiding unnecessary demerging and remerging of multi‐commodity integer flows
    Networks (IF 2.602) Pub Date : 2020-07-21
    Zhiyuan Lin; Raymond S. K. Kwan

    Resource flows may merge and demerge at a network node. Sometimes several demerged flows may be immediately merged again, but in different combinations compared to before they were demerged. However, the demerging is unnecessary in the first place if the total resources at each of the network nodes involved remains unchanged. We describe this situation as “unnecessary demerging and remerging (UDR)”

  • Delivery systems with crowd‐sourced drivers: A pickup and delivery problem with transfers
    Networks (IF 2.602) Pub Date : 2020-07-10
    Afonso Sampaio; Martin Savelsbergh; Lucas P. Veelenturf; Tom Van Woensel

    Rapid urban growth, the increasing importance of e‐commerce and high consumer service expectations have given rise to new and innovative models for freight delivery within urban environments. Crowdsourced solutions—where drivers are not employed by a carrier but occasionally offer their services through on‐line platforms and are contracted as required by carriers—are receiving growing attention from

  • Adaptive large variable neighborhood search for a multiperiod vehicle and technician routing problem
    Networks (IF 2.602) Pub Date : 2020-06-22
    Benjamin Graf

    The VeRoLog Solver Challenge 2018–2019 of the EURO working group vehicle routing and logistics (VeRoLog) considers a multiperiod vehicle and technician routing and scheduling problem. This paper proposes a combination of large neighborhood and local search heuristics and a decomposition approach to efficiently generate competitive solutions under restricted computational resources. The interplay of

  • Columnwise neighborhood search: A novel set partitioning matheuristic and its application to the VeRoLog Solver Challenge 2019
    Networks (IF 2.602) Pub Date : 2020-06-20
    Caroline J. Jagtenberg; Oliver J. Maclaren; Andrew J. Mason; Andrea Raith; Kevin Shen; Michael Sundvick

    This article reports on an approach for the VeRoLog Solver Challenge 2019: the fourth solver challenge facilitated by VeRoLog, the EURO Working Group on Vehicle Routing and Logistics Optimization. The authors were awarded third place in this challenge. The routing challenge involved solving two interlinked vehicle routing problems for equipment: one for distribution (using trucks) and one for installation

  • Exact and hyper‐heuristic solutions for the distribution‐installation problem from the VeRoLog 2019 challenge
    Networks (IF 2.602) Pub Date : 2020-06-29
    Ahmed Kheiri; Leena Ahmed; Burak Boyacı; Joaquim Gromicho; Christine Mumford; Ender Özcan; Ali Selim Dirikoç

    This work tackles a rich vehicle routing problem (VRP) problem integrating a capacitated vehicle routing problem with time windows (CVRPTW), and a service technician routing and scheduling problem (STRSP) for delivering various equipment based on customers' requests, and the subsequent installation by a number of technicians. The main objective is to reduce the overall costs of hired resources, and

  • Optimizing the investments in mobile networks and subscriber migrations for a telecommunication operator
    Networks (IF 2.602) Pub Date : 2020-07-25
    Adrien Cambier; Matthieu Chardy; Rosa Figueiredo; Adam Ouorou; Michael Poss

    We consider the context of a telecommunication company that is at the same time an infrastructure operator and a service provider. When planning its network expansion, the company can leverage over its knowledge of the subscriber dynamic to better optimize the network dimensioning, therefore avoiding unnecessary costs. In this work, the network expansion represents the deployment and/or reinforcement

  • A novel pseudo‐polynomial approach for shortest paths problems
    Networks (IF 2.602) Pub Date : 2020-07-14
    Milos Danilovic; Dragan Vasiljevic; Biljana Cvetic

    This article presents a novel shortest‐paths algorithm for connected networks with non‐negative edge weights. The worst case running time of the Single Source Shortest Path version of the algorithm is O (max(m , )) where m is the number of edges of the input network, and , the normalized eccentricity of the source vertex. The pseudo‐polynomial nature of the time dependence is overcome with simple speed‐up

  • Arc routing problems: A review of the past, present, and future
    Networks (IF 2.602) Pub Date : 2020-06-29
    Ángel Corberán; Richard Eglese; Geir Hasle; Isaac Plana; José María Sanchis

    Arc routing problems (ARPs) are defined and introduced. Following a brief history of developments in this area of research, different types of ARPs are described that are currently relevant for study. In addition, particular features of ARPs that are important from a theoretical or practical point of view are discussed. A section on applications describes some of the changes that have occurred from

  • Improved methods to compare distance metrics in networks using uniform random spanning trees (DIMECOST)
    Networks (IF 2.602) Pub Date : 2020-06-10
    Sara Bourbour; Dinesh P. Mehta; William C. Navidi

    We consider the network analytics problem of comparing two distance metrics on the same set of n entities. The classical solution to this problem is the Mantel test, which uses permutation testing to accept or reject the null hypothesis that there is “no relationship between the two metrics.” Its computational complexity is n2 times the number of permutations (based on a user supplied parameter). This

  • The stochastic critical node problem over trees
    Networks (IF 2.602) Pub Date : 2020-05-29
    Pierre Hosteins; Rosario Scatamacchia

    We tackle a stochastic version of the critical node problem (CNP) where the goal is to minimize the pairwise connectivity of a graph by attacking a subset of its nodes. In the stochastic setting considered, the outcome of attacks on nodes is uncertain. In our work, we focus on trees and demonstrate that over trees the stochastic CNP actually generalizes to the stochastic critical element detection

  • An integer program for positive semidefinite zero forcing in graphs
    Networks (IF 2.602) Pub Date : 2020-05-09
    Logan A. Smith; Derek J. Mikesell; Illya V. Hicks

    Positive semidefinite (PSD) zero forcing is a dynamic graph process in which an initial subset of vertices are colored and may cause additional vertices to become colored through a set of color changing rules. Subsets which cause all other vertices to become colored are called PSD zero forcing sets; the PSD zero forcing number of a graph is the minimum cardinality attained by its PSD zero forcing sets

  • Empirical study on sufficient numbers of minimum cuts in strongly connected directed random graphs
    Networks (IF 2.602) Pub Date : 2020-05-05
    Eric Chang; C. K. Cheng; Anushka Gupta; Po‐Ya Hsu; Amanda Moffitt; Alissa Ren; Irene Tsaur; Samuel Wang

    We focus on the all‐pairs minimum cut (APMC) problem, a graph partitioning problem whose solution requires finding the minimum cut for every pair of nodes in a given graph. While it is solved for undirected graphs, a solution for APMC in directed graphs still requires an O (n 2) brute force approach. We show that the empirical number of distinct minimum cuts in randomly generated strongly connected

  • On the road to better routes: Five decades of published research on the vehicle routing problem
    Networks (IF 2.602) Pub Date : 2020-04-24
    Xingyin Wang; Edward Wasil

    For nearly 50 years, Networks has been at the forefront of routing research and practice with more than 140 articles in print with tens of thousands of citations. These articles span the development of solution procedures to reporting practical applications. We identify key areas of contribution including exact algorithms, heuristics, arc routing, and periodic routing, and provide detailed annotations

  • Spanning tree modulus for secure broadcast games
    Networks (IF 2.602) Pub Date : 2020-04-21
    Nathan Albin; Kapila Kottegoda; Pietro Poggi‐Corradini

    The theory of p‐modulus provides a general framework for quantifying the richness of a family of objects on a graph. When applied to the family of spanning trees, p‐modulus has an interesting probabilistic interpretation. In particular, the 2‐modulus problem in this case has been shown to be equivalent to the problem of finding a probability distribution on spanning trees that utilizes the edges of

  • The K‐partitioning problem: Formulations and branch‐and‐cut
    Networks (IF 2.602) Pub Date : 2020-04-21
    Zacharie Ales; Arnaud Knippel

    The K‐partitioning problem consists in partitioning the nodes of a complete graph G = (V, E) with weights on the edges in exactly K clusters such that the sum of the weights of the edges inside the clusters is minimized. For this problem, we propose two node‐cluster formulations adapted from the literature on similar problems as well as two edge‐representative formulations. We introduced the first

  • A branch‐and‐cut approach for the least cost influence problem on social networks
    Networks (IF 2.602) Pub Date : 2020-04-10
    Dilek Günneç; S. Raghavan; Rui Zhang

    This paper studies a problem in the online targeted marketing setting called the least cost influence problem (LCIP) that is known to be NP‐hard. The goal is to find the minimum total amount of inducements (individuals to target and associated tailored incentives) required to influence a given population. We develop a branch‐and‐cut approach to solve this LCIP on arbitrary graphs. We build upon Günneç

  • Rational roots of all‐terminal reliability
    Networks (IF 2.602) Pub Date : 2020-04-09
    Jason I. Brown; Corey D. C. DeGagné

    Given a connected graph G whose vertices are perfectly reliable and whose edges each fail independently with probability q  ∈ [0, 1], the (all‐terminal ) reliability of G is the probability that the resulting subgraph of operational edges contains a spanning tree (this probability is always a polynomial in q ). The location of the roots of reliability polynomials has been well studied, with particular

  • Resilience of communication networks to random failures and disasters: An optimization perspective
    Networks (IF 2.602) Pub Date : 2020-03-27
    Jacek Rak; Poul E. Heegaard; Bjarne E. Helvik

    Communication networks are subject to many challenges leading to single or multiple failures of its elements. Example failure scenarios include unintentional failures due to scheduled maintenance activities or massive failures caused by disaster‐induced events. Therefore, it is crucial to enhance the networks with redundancy and resilience mechanisms able to maintain the availability of network services

  • Routing and scheduling of network flows with deadlines and discrete capacity allocation
    Networks (IF 2.602) Pub Date : 2020-03-24
    Ghafour Ahani; Pawel Wiatr; Di Yuan

    Joint scheduling and routing of data flows with deadline constraints in communication networks has been attracting research interest. This type of problem distinguishes from conventional multicommodity flows due to the presence of the time dimension. In this paper, we address a flow routing and scheduling problem with delivery deadline, where the assignment of link capacity occurs in discrete units

  • Linear edge costs and labeling algorithms: The case of the time‐dependent vehicle routing problem with time windows
    Networks (IF 2.602) Pub Date : 2020-03-19
    Gonzalo Lera‐Romero; Juan J. Miranda Bront; Francisco J. Soulignac

    In this paper we implement a branch‐price and cut algorithm for a time dependent vehicle routing problem with time windows in which the goal is to minimize the total route duration. The travel time between two customers is given by a piecewise linear function on the departure time and, thus, it need not remain fixed along the planning horizon. We discuss different alternatives for the implementation

  • The Earth is nearly flat: Precise and approximate algorithms for detecting vulnerable regions of networks in the plane and on the sphere
    Networks (IF 2.602) Pub Date : 2020-03-06
    Balázs Vass; László Németh; János Tapolcai

    Several recent works shed light on the vulnerability of networks against regional failures, which are failures of multiple pieces of equipment in a geographical region as a result of a natural disaster. To enhance the preparedness of a given network to natural disasters, regional failures and associated Shared Risk Link Groups (SRLGs) should be first identified. For simplicity, most of the previous

  • Robust network function virtualization
    Networks (IF 2.602) Pub Date : 2020-03-04
    Tachun Lin; Zhili Zhou

    Network function virtualization (NFV) enables on‐demand network function (NF) deployment providing agile and dynamic network services. Through an evaluation metric that quantifies the minimal reliability among all NFs for all demands, service providers and operators may better facilitate flexible NF service recovery and migration, thus offering higher service reliability. In this paper, we present

  • Dual‐failure restorability analysis of span‐restorable meta‐mesh networks
    Networks (IF 2.602) Pub Date : 2020-02-26
    Andres Castillo; Tetsuhei Nakashima‐Paniagua; John Doucette

    The span‐restorable meta‐mesh model was previously designed as a cutting‐edge technique that enhanced the spare capacity efficiency in low average nodal degree networks. In this technique, lightpaths that fully traverse chains of degree‐2 nodes are provided with a logical express bypass span allowing a distinction between the internal and external working flow capacity that transit the chain. In the

  • Design/upgrade of a transparent optical network topology resilient to the simultaneous failure of its critical nodes
    Networks (IF 2.602) Pub Date : 2020-02-12
    Fábio Barbosa; Amaro de Sousa; Agostinho Agra

    This paper addresses two related problems in the context of transparent optical networks. In the network design problem, the aim is to identify a set of fiber links to connect a given set of nodes. In the network upgrade problem, the aim is to identify a set of new fiber links to add to a given network topology. For a given fiber length budget, the aim in both problems is to maximize the network resilience

  • The policy graph decomposition of multistage stochastic programming problems
    Networks (IF 2.602) Pub Date : 2020-02-12
    Oscar Dowson

    We propose the policy graph as a structured way of formulating a general class of multistage stochastic programming problems in a way that leads to a natural decomposition. We also propose an extension to the stochastic dual dynamic programming algorithm to solve a subset of problems formulated as a policy graph. This subset includes discrete‐time, convex, infinite‐horizon, multistage stochastic programming

  • A robust optimization model for affine/quadratic flow thinning: A traffic protection mechanism for networks with variable link capacity
    Networks (IF 2.602) Pub Date : 2020-02-11
    Ilya Kalesnikau; Michał Pióro; Michael Poss; Dritan Nace; Artur Tomaszewski

    Flow thinning (FT) is a traffic protection mechanism for communication networks with variable link capacities, for example wireless networks. With FT, end‐to‐end traffic demands use dedicated logical tunnels, for example MPLS tunnels, whose nominal capacity is subject to thinning in order to follow fluctuations in link capacities availability. Moreover, instantaneous traffic of each demand is throttled

  • Shared Risk Link Group disjointness and geodiverse routing: A trade‐off between benefit and practical effort
    Networks (IF 2.602) Pub Date : 2020-02-07
    Rita Girão‐Silva; Boro Nedic; Matthias Gunkel; Teresa Gomes

    The resilience to disasters is a very relevant problem in telecommunication networks. This work addresses the problem of 1 + 1 optical lightpath protection considering maximally shared risk link group (SRLG)‐disjoint geodiverse paths, applied in the context of an optical network. The resilience to geographically correlated disasters is accomplished by guaranteeing geodiversity of the paths. This work

  • Content placement in 5G‐enabled edge/core data center networks resilient to link cut attacks
    Networks (IF 2.602) Pub Date : 2020-02-04
    Carlos Natalino; Amaro de Sousa; Lena Wosinska; Marija Furdek

    High throughput, resilience, and low latency requirements drive the development of 5G‐enabled content delivery networks (CDNs) which combine core data centers (cDCs) with edge data centers (eDCs) that cache the most popular content closer to the end users for traffic load and latency reduction. Deployed over the existing optical network infrastructure, CDNs are vulnerable to link cut attacks aimed

  • Networks in economics and finance in Networks and beyond: A half century retrospective
    Networks (IF 2.602) Pub Date : 2019-11-15
    Anna Nagurney

    This paper presents a panoramic view of research on economic and financial networks in the journal Networks, since its inception half a century ago. This paper focuses on both the breadth and depth of the journal articles, and within the context of earlier contributions, as well as more recent related ones in other scientific publications. From network optimization to game theory and a plethora of

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