Skip to main content

Bernard Cousin

Université de Rennes, IRISA, Faculty Member

Followers

64

Following

6

Co-authors

22

Public Views

Bernard A. Cousin is Professor of the University of Rennes. He is member of IRISA - Institut de Recherche en Informatique et Systèmes Aléatoires. He was member of IRT Bcom. Both are research consortium. His scientific research interests cover Computer Communications (Networking), Computer Security and Reliability, Network Routing, their protocols or algorithms.

less

Interests

Uploads

Papers by Bernard Cousin

Etude de la resynchronisation d'un protocole de communication

HAL (Le Centre pour la Communication Scientifique Directe), May 1, 1987

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Multicast Routing and Wavelength Assignment in WDM Mesh Networks with Sparse Splitting

HAL (Le Centre pour la Communication Scientifique Directe), Dec 7, 2009

In this paper routing and wavelength assignment for supporting multicast traffic is investigated ... more In this paper routing and wavelength assignment for supporting multicast traffic is investigated in WDM mesh networks under sparse splitting constrain. This problem is generally solved in two phases respectively with the purpose of minimizing the number of wavelengths required. Alternative routing is first proposed to route each session by pre-computing a set of candidate light-forests. Then wavelength assignment is formulated as a coloring problem by constructing a conflict graph. Potential heuristic algorithms are proposed.

Optical power control to efficiently handle flex-grid spectrum gain over existing fixed-grid network infrastructures

The exponential traffic growth in optical networks has triggered the evolution from Fixed-Grid to... more The exponential traffic growth in optical networks has triggered the evolution from Fixed-Grid to Flex-Grid technology. This evolution allows better spectral efficiency and spectrum usage over current networks in order to facilitate dynamic and huge traffic demands. The integration of Flex-Grid technology increases the number of optical channels established over optical links, leading, however, to an increase in amplification power and possibly saturating optical amplifiers. In this work, we propose a power adaptation process that takes advantage of link optical signal to noise ratio (OSNR) margins to allow network operators to support this power increase while maintaining the use of legacy amplifiers. Results show that controlling channel optical power benefits from the Flex-Grid in terms of spectrum and capacity gain using in-place amplifier infrastructure.

Optical Power Control in GMPLS Control Plane

Journal of Optical Communications and Networking, Jul 21, 2016

The exponential traffic growth in optical networks has triggered the evolution from Fixed-Grid to... more The exponential traffic growth in optical networks has triggered the evolution from Fixed-Grid to Flex-Grid technology. This evolution allows better spectral efficiency and spectrum usage over current optical networks in order to facilitate huge dynamic traffic demands. The promise of Flex-Grid technology in terms of increasing the number of optical channels established over optical links may however not be sustainable because of the associated increase in optical amplification power. In this work, we detail a power control process that takes advantage of link optical power and channel optical signal to noise ratio (OSNR) margins to allow network operators to support this optical power increase while maintaining the use of legacy optical amplifiers. New GMPLS protocol extensions are proposed to integrate the optical power control process in the control plane. The performance of the process is evaluated in terms of the blocking ratio and network throughput over Fixed-Grid and Flex-Grid networks. Results show that controlling optical power benefits from the Flex-Grid technology in terms of spectrum and capacity gain and reduces optical connection blocking.

Optical Power Control in Translucent Flexible Optical Networks With GMPLS Control Plane

Journal of Optical Communications and Networking, Aug 9, 2018

The continuously increasing traffic of Internet services (cloud services, video streaming, social... more The continuously increasing traffic of Internet services (cloud services, video streaming, social networks and recently Internet of things services) is leading to a huge traffic growth in the core optical networks. This traffic evolution is pushing network operators to exploit efficiently their infrastructures in order to postpone, as much as possible, the expensive deployment of new infrastructures. In this respect, the migration from fixed to flex-grid optical networks was triggered in order to efficiently use optical network capacity taking benefits from the improved spectral efficiency of flexible transponders. In our previous work [1], we demonstrated that migrating towards flexible networks while keeping in use existing optical amplifiers will cause power saturation problem over highly loaded links due to the increase in the number of optical channels. To overcome this problem, we proposed in [1] a power adaptation process that consists on converting transmission performance margins into optical power attenuation over optical links. However, the realized work considered only transparent optical network controlled by GMPLS protocol suite. In this paper, we consider the case of translucent optical network where optical regeneration is required and thus the power adaptation process is adapted to such kind of network. New routing algorithm and protocol extensions are proposed to take into account power and regeneration information in the GMPLS control plane of translucent networks.

Avoidance of multicast incapable branching nodes for multicast routing in WDM networks

Although many multicast routing algorithms have been proposed in order to reduce the total cost i... more Although many multicast routing algorithms have been proposed in order to reduce the total cost in WDM optical networks, the link stress and delay are two parameters which are not always taken into consideration. This paper proposes a novel wavelength routing algorithm, which tries to avoid the multicast incapable branching nodes (MIB, branching nodes without splitting capability) to diminish the link stress for the shortest path based multicast tree and maintains good parts of the shortest path tree to reduce the end-to-end delay. Firstly a DijkstraPro algorithm with priority assignment and node adoption is introduced to produce a shortest path tree with up to 38% fewer MIB nodes, and then critical articulation and deepest branch heuristics are used to process the MIB nodes. Finally distance based reconnection algorithm is proposed to create the multicast tree or forest.

Application-aware protection in DWDM optical networks

Fast recovery time and reduced resource utilization are the two main criteria for determining the... more Fast recovery time and reduced resource utilization are the two main criteria for determining the quality of survivability mechanism. Now it is well-known that link-based protection and path-based protection provide respectively a short recovery time and reduced use of resources. To benefit from the both of these saliencies, we propose in this paper to use these mechanisms simultaneously. Indeed, demands mandating shorter recovery time will be protected using link-based protection. Meanwhile other demands will be protected using pathbased protection. Simulation results show that the proposed solution achieves a good trade-off between resource utilization and recovery time.

Optimized Design of Survivable MPLS over Optical Transport Networks. Optical Switching and Networking

arXiv (Cornell University), Oct 21, 2007

In this paper we study different options for the survivability implementation in MPLS over Optica... more In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the traffic granularity on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with actual technology pricing and were obtained for networks targeted to a nationwide coverage.

Hierarchical Structure and Placement of MC Node in Optical WDM Network

Lecture notes in networks and systems, 2023

Multicast Routing and Wavelength Assignment in WDM Mesh Networks with Sparse Splitting

HAL (Le Centre pour la Communication Scientifique Directe), Dec 7, 2009

In this paper routing and wavelength assignment for supporting multicast traffic is investigated ... more In this paper routing and wavelength assignment for supporting multicast traffic is investigated in WDM mesh networks under sparse splitting constrain. This problem is generally solved in two phases respectively with the purpose of minimizing the number of wavelengths required. Alternative routing is first proposed to route each session by pre-computing a set of candidate light-forests. Then wavelength assignment is formulated as a coloring problem by constructing a conflict graph. Potential heuristic algorithms are proposed.

Contracts and Grants with Industry - ASSET : Architectural Solutiuons for Services Enhancing digital television, 1 02 C0349

Tree Reconfiguration without Lightpath Interruption in Wavelength Division Multiplexing Optical Networks with Limited Resources

HAL (Le Centre pour la Communication Scientifique Directe), Apr 1, 2014

Today, operators use reconfiguration to improve the performance of connection oriented networks. ... more Today, operators use reconfiguration to improve the performance of connection oriented networks. In our previous work, we studied tree reconfiguration without data flow interruption in WDM optical networks. In our previous approach, the available resources of the network (wavelengths) are not considered as limited. In this work, we study tree reconfiguration in a network which has a limited number of wavelengths per link. This paper proposes an algorithm called TRwRC (tree reconfiguration with resources constraint). TRwRC reconfigures a tree without data flow interruption in a network with a limited number of wavelengths.

Dissemination - Standardisation activities

Performance evaluation of TcpHas: TCP for HTTP adaptive streaming

Multimedia Systems, Mar 31, 2018

HTTP Adaptive Streaming (HAS) is a widely used video streaming technology that suffers from a deg... more HTTP Adaptive Streaming (HAS) is a widely used video streaming technology that suffers from a degradation of user's Quality of Experience (QoE) and network's Quality of Service (QoS) when many HAS players are sharing the same bottleneck link and competing for bandwidth. The two major factors of this degradation are: the large OFF period of HAS, which causes false bandwidth estimations, and the TCP congestion control, which is not suitable for HAS given that it does not consider the different video encoding bitrates of HAS. This paper proposes a HAS-based TCP congestion control, TcpHas, that minimizes the impact of the two aforementioned issues. It does this by using traffic shaping on the server. Simulations indicate that TcpHas improves both QoE, mainly by reducing instability and convergence speed, and QoS, mainly by reducing queuing delay and packet drop rate.

Dissemination - Standardization activities

Sub-tree Pair Selection for Reconfiguration of a Light-tree Pair

HAL (Le Centre pour la Communication Scientifique Directe), Nov 21, 2019

Reconfiguration of unicast or multicast connections in an optical network is a critical task. Ind... more Reconfiguration of unicast or multicast connections in an optical network is a critical task. Indeed, if it is not carried out correctly, it can lead to optical flow (also called flow) interruptions that can cause damage to the network operator. It is therefore common to perform the reconfiguration in several steps. In this study, we focused on multicast connection reconfiguration because multicast connection become more attractive and efficient technique to transmit flow of multicast applications. A Multicast connection in an optical network can be represented by a point-tomultipoint all-optical path called light-tree. In short, we explain how to select a pair of sub-trees (current sub-tree, new sub-tree) to be reconfigured at a given step of the reconfiguration process.

Performance Evaluation of Integrated Access and Backhaul in 5G Networks

2021 IEEE Conference on Standards for Communications and Networking (CSCN), 2021

Integrated Access and Backhaul (IAB) allows to ease the deployment of gNodeBs (gNBs) in a 5G netw... more Integrated Access and Backhaul (IAB) allows to ease the deployment of gNodeBs (gNBs) in a 5G network by connecting them using cellular connectivity. The radio frequencies to achieve such a result can be the same as the ones used to connect User Equipment (UE) (in-band) or specific ones can be reserved (out-of-band). Both sub 6 GHz and millimeter wave (mmWave) frequencies can be used. IAB is relatively new and several contributions have been studying the lower layers (i.e. physical and link) in order to improve performance in scheduling and resource allocation. However, performance results are also very dependent on how the routing is implemented at the network layer which is an aspect that is not much studied in the state of the art. In this paper, we evaluate the performance of several IAB topologies against a topology without IAB-nodes. Results confirm the conclusions of the state of the art by showing that adding IABnodes significantly improve performance in terms of delay (more than 90 ms shorter delay) and Packet Delivery Ratio (PDR) (by up to 15%), and also allows to extend the coverage area. These results reveal the high potential of IAB that could be improved even more using efficient routing.

User Selection in 5G Heterogeneous Networks Based on Millimeter-Wave and Beamforming

2018 IEEE 20th International Conference on High Performance Computing and Communications; IEEE 16th International Conference on Smart City; IEEE 4th International Conference on Data Science and Systems (HPCC/SmartCity/DSS), 2018

Heterogeneous Networks (HetNETs) are considered as an effective solution to improve the coverage ... more Heterogeneous Networks (HetNETs) are considered as an effective solution to improve the coverage and system throughput for future cellular networks. The extremely growing mobile market, together with the arising demand for high data rates, motivate us to open a new spectrum related to millimeter waves (mmwaves) while using beamforming that can serve simultaneously a group of users. In this paper, we formulate an optimization problem for HetNETs multiuser selection in a multi-input-multi-output and orthogonal frequency-division multiple access (MIMO-OFDMA) system, aiming to maximize the total system throughput. We solve the problem by applying a modified version of well-known metaheuristic algorithms. The optimal solution is obtained using an exhaustive search algorithm that provides an ideal solution which is complex to be computed. Greedy zero-forcing dirty-paper gZF-DP and zeroforcing selection ZFS algorithms were selected from literature for the sub-optimal solution. In parallel, a water-filling algorithm has been optimized after adding new power constraint and it has been used for power distribution. Hence, we analyze the throughput performance of our systems using throughput metric. The results show that ZFS outperforms gZF-DP algorithm as it achieves higher total throughput, While gZF-DP outperforms ZFS algorithm in the execution time.

Equal Cost Multiple Path Energy-Aware Routing in Carrier-Ethernet Networks with Bundled Links

2017 IEEE/ACS 14th International Conference on Computer Systems and Applications (AICCSA), 2017

The reduction of operational expenditure has become a major concern for telecommunication operato... more The reduction of operational expenditure has become a major concern for telecommunication operators and Internet service providers. In this paper, we propose an energy aware routing (EAR) in Carrier Ethernet networks operating with Shortest Path Bridging (SPB) protocol with equal cost multi-path (ECMP). Since traffic load has no influence on power consumption of Carrier Ethernet network elements, the conventional solution to reduce power consumption is to find the maximal set of network elements that can be turned off/on so that the network performance is not deteriorated. To tackle this optimization problem, we propose an exact method based on Mixed Integer Linear Programming (MILP) formulation, called SPB energy-aware routing (SPB-EAR). Since SPB-EAR is proved to be NP-hard, we present two heuristics algorithm suitable for large-sized networks, called Green SPB (G-SPB) and Fast Greedy SPB (FG-SPB). In this work, we consider that a connection between two nodes is represented by bundled link consisting of multiple cables. Experimentations on four realistic network topologies show that G-SPB and FG-SPB can save almost as much power consumption as SPB-EAR.

Efficient Placement of Splitters in Optical WDM Network

In this paper, we investigate the splitter placement problem in an optical WDM network. The goal ... more In this paper, we investigate the splitter placement problem in an optical WDM network. The goal is to select a given number of MC nodes in the network such that the overall link cost of a multicast session is minimized. We present an exact formulation in integer linear programming ( ILP ) to find a set of trees that connects a source to a set of destination nodes. Then, four algorithms based on network topology metrics are proposed to select a given number of MC nodes in the network such that the overall link cost of a multicast session is minimized. The efficiency of the proposed algorithms is verified by simulation results.