Digital Communications and Networks xxx (2017) 1–2 Contents lists available at ScienceDirect Digital Communications and Networks journal homepage: www.elsevier.com/locate/dcan Editorial: Special issue on “Resilient networks: Modeling, design, and applications” The design of resilient networks is of utmost importance today, owing to the wide range of safety-critical applications. Resilient networks try to guarantee an acceptable level of Quality of Service (QoS), even in cases of challenges and faults in the system. The causes of obstruction in normal system operation range from simple misconfiguration, hardware failures, and software failures to intended attacks and natural disasters. To enable the resilience of a network, it is important to identify the causes of faults and challenges, and to take necessary measures to protect the services from being affected. Considering the massive increase in the number of applications running on the Internet, and the significant societal and economic consequences of their outages, this special issue offers an overview of the state-of-the-art technology and the research advances on issues, challenges, and potential solutions for modeling and designing resilient networks. We are excited to have received 24 submissions in total for this special issue from the authors of the 4th International Conference on Advanced Computing, Networking, and Informatics (ICACNI 2016) as well as extended works from independent authors responding to our open call. After a strict peer review and revision process, only seven articles were selected to be featured in this special issue. The selected papers cover various aspects of resilient networks, namely, QoS routing protocols ([1,2]), network security ([3]), fault recovery ([4,5]), and effective service selection ([6,7]). The first two articles highlight the development of QoS routing protocols for efficient communication. In the first article, titled “QoS aware routing and wavelength allocation in optical burst switching networks using differential evolution optimization” [1], the authors present a QoSaware routing and wavelength allocation (RWA) technique for burst switching in optical burst-switching networks. The authors model the problem as a bi-objective integer linear programming (ILP) problem. The goals are to minimize both the number of wavelengths used and the number of hops traversed by the optical signal, from source to a given destination. The authors propose a novel approach to solve the minimization problem using differential evolution, which outperforms the shortest-path routing algorithm. The second article in this category, titled “Trade-off between accuracy, cost and QoS using Beacon on Demand strategy and Kalman filtering over VANET” [2], presents an improved Greedy Perimeter Stateless Routing (GPSR) protocol for VANET, in which the vehicles can estimate the positions of their neighbors using a Kalman filter algorithm. This protocol reduces the frequency of beacon exchanges compared with that of the broadcasting periodic beaconing used in GPSR. The proposed protocol is supplemented with a “Beacon on Demand” process, through which a node can explicitly discover its neighborhood whenever required. The packet delivery ratio, routing cost, normalized routing load, end-to-end delay, and throughput are found to be better in the improved routing protocol than they are in GPSR, AODV, DSR, and ZRP. The third article, titled “An improved and secure multi-server authentication scheme based on biometrics and smartcard” [3], focuses on secure multi-server authentication using a master server. Instead of authenticating with each desired server independently, which requires multiple access credentials, the authors suggest using a master server for authentication. To augment the authentication scheme, the authors consider reading users' biometric information from a smartcard while authenticating. The security analysis and simulation results ratify the efficiency of the proposed scheme. The next set of two papers examine the efficient recovery of services after system failure. The fourth article, titled “PRECESION: Progressive recovery and restoration planning of interdependent services in enterprise data centers” [4], studies the order of recovering interdependent services, and the impact on downtime of a data center failure. In the case of a major disruption in a data center, the multi-stage recovery mechanism focuses on the fast and efficient restoration of services so to achieve a lower downtime. The progressive return of applications and services supports partial business continuity. Using efficient metaheuristics, the authors show that the proper order of recovering interdependent services has a favourable impact on effective downtime. In the fifth article, titled “Increasing public safety broadband network resiliency through traffic control” [5], the authors suggest a traffic control mechanism that exploits variable modulation and coding to enhance the recovery of the Public Safety Broadband Network after a failure. Subsequent to tower outages, the coverage for high-priority users responding to an emergency incident is increased by preempting the service to other low-priority users. The final two articles discuss the impact of proper service selection on the efficiency of the system. In the sixth article, titled “Effects of threshold based relay selection algorithms on the performance of an IEEE 802.16j Mobile Multi-hop Relay (MMR) WiMAX network” [6], the authors investigate the effects of relay selection algorithms on performance metrics such as the symbol error rate (SER) and the channel capacity in an IEEE 802.16j mobile multi-hop relay WiMAX network. The simulation study confirms that the performance of the proposed relay selection algorithms, namely, threshold-based max-min and threshold-based harmonic mean of SNR, is better than that of the existing max-min and harmonic mean of SNR-based algorithms. The seventh and last article of the special issue, titled “Transmission in mobile cloudlet systems with intermittent connectivity in emergency areas” [7], concentrates on the dynamic cloudlet selection policy, based on the Borda Scores Method https://doi.org/10.1016/j.dcan.2017.10.003 Available online xxxx 2352-8648/© 2017 Chongqing University of Posts and Telecommunications. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: A. Elci, et al., Editorial: Special issue on “Resilient networks: Modeling, design, and applications”, Digital Communications and Networks (2017), https://doi.org/10.1016/j.dcan.2017.10.003 A. Elci et al. Digital Communications and Networks xxx (2017) 1–2 Dr. Sambit Bakshi is currently with the Center for Computer Vision and Pattern Recognition of the National Institute of Technology Rourkela, India. He also serves as assistant professor in the Department of Computer Science & Engineering of the institute. He earned his PhD degree in Computer Science & Engineering in 2015. His research interests include social security, surveillance systems, and human computer interaction. He serves as associate editor of IEEE Access (2016 -), Plos One (2017 -), Innovations in Systems and Software Engineering - A NASA Journal (2016 -), and the International Journal of Biometrics (2013 -). He is a technical committee member of the IEEE Computer Society Technical Committee on Pattern Analysis and Machine Intelligence. He received the prestigious Innovative Student Projects Award 2011 from the Indian National Academy of Engineering (INAE) for his masters thesis. He has more than 50 publications in journals, reports, conferences. (BSM), to offload applications from mobile devices in mobile cloudlet systems. The selected cloudlet may execute the offloaded applications locally, or may further offload them to the cloud selected using existing the Cloud Probing Service (CPS) and Cloud Ranking Service (CRS). To conclude, we thank all reviewers and Editors-in-Chief Prof. Chonggang Wang, Prof. Huosheng Hu, and Prof. Jinzhao Lin who have ensured the high quality of the articles through their insights and constant efforts. We hope you will find these articles scientifically appealing. References [1] R. Barpanda, A. Turuk, B. Sahoo, QoS aware routing and wavelength allocation in optical burst switching networks using differential evolution optimization, Digit. Commun. Netw. (2017), http://dx.doi.org/10.1016/j.dcan.2017.09.002. [2] Z. Squalli, I. Zaimi, M. Drissi, M. Oumsis, S. Ouatik, Trade-off between accuracy, cost and QoS using Beacon on Demand strategy and Kalman filtering over VANET, Digit. Commun. Netw. (2017), http://dx.doi.org/10.1016/j.dcan.2017.09.001. [3] A. Kumar, H. Om, An improved and secure multi-server authentication scheme based on biometrics and smartcard, Digit. Commun. Netw. (2017), http://dx.doi.org/ 10.1016/j.dcan.2017.09.004. [4] I. El-Shekeil, A. Pal, K. Kant, PRECESION: Progressive recovery and restoration planning of interdependent services in enterprise data centers, Digit. Commun. Netw. (2017), http://dx.doi.org/10.1016/j.dcan.2017.08.001. [5] R. Rouil, W. Garey, C. Gentile, N. Golmie, P. Schwinghammer, Increasing public safety broadband network resiliency through traffic control, Digit. Commun. Netw. (2017), http://dx.doi.org/10.1016/j.dcan.2017.09.005. [6] C. Swain, S. Das, Effects of threshold based relay selection algorithms on the performance of an IEEE 802.16j mobile multi-hop relay (MMR) WiMAX network, Digit. Commun. Netw. (2017), http://dx.doi.org/10.1016/j.dcan.2017.09.003. [7] C. Panigrahi, J. Sarkar, B. Pati, Transmission in mobile cloudlet systems with intermittent connectivity in emergency areas, Digit. Commun. Netw. (2017), http:// dx.doi.org/10.1016/j.dcan.2017.09.006. Dr. Manmath Narayan Sahoo received his PhD. degree in Computer Science in 2014 from the National Institute of Technology Rourkela, India. He is an assistant professor in the Department of Computer Science and Engineering, National Institute of Technology Rourkela, India. He has served as a reviewer, guest editor, general chair, and program chair in many reputed journals and conferences. His research interests include Mobile Ad hoc Networks, Fault Tolerance, Sensor Networks, and Cloud Computing. Atilla Elci*, Sambit Bakshi, Manmath N. Sahoo Department of Computer Science and Engineering, National Institute of Technology Rourkela, Odisha, 769 008, India Prof. Atilla Elci is currently with Aksaray University, Cappadocia, Turkey, where he serves as the Chairman of the Electrical-Electronics Engineering Department. His areas of interest include Artificial Intelligence, Semantic Web, Security, and Robotics. He is an associate editor of Expert Systems: The Journal of Knowledge Engineering and editorial board member of several other journals. He has served as Program Chair of 36th IEEE Signature Conference on Computers, Software, and Applications (COMPSAC 2012). He has authored numerous articles in reputed journals and conferences. * 2 Corresponding author. Department of Electrical and Electronics Engineering, Aksaray University, Aksaray, Turkey. E-mail addresses: atilla.elci@gmail.com (A. Elci), sambitbaksi@gmail.com, bakshisambit@nitrkl.ac.in (S. Bakshi), sahoom@nitrkl.ac.in (M.N. Sahoo).