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The evolution of data-intensive services and applications continues to drive the need for higher data rates in wireless communication systems, consequently depleting the radio frequency (RF) spectrum. Due to the unlicensed and enormous bandwidth available in the visible light (VL) spectrum, the emergence of visible light communication (VLC) has been considered a potential solution to alleviate the constraints associated with RF spectrum scarcity. However, the line-of-sight requirement and the inability of VL to penetrate opaque obstacles remain a daunting challenge in realizing a wider coverage area. The incorporation of cooperative communication in VLC systems serves as one of the primary solutions to address this challenge. Though various investigations are currently being conducted in this domain, a holistic report of various advances, solution approaches, and design challenges has not been captured in the open literature. Therefore, in this paper, our main goal is to present a review of the state-of-the-art research on cooperative VLC systems. Firstly, we provide a background discussion to establish the relationship between various components of cooperative VLC systems from a theoretical and analytical perspective. Secondly, we categorize various contributions in this direction under media access control (MAC), hybrid VLC-RF, power line communication-VLC (PLC-VLC), and VLC with energy harvesting. Based on the established categories, we identify various system design and evaluation methods, optimization problems, solution approaches adopted to tackle the problems, and their limitations. Thirdly, we identify various insights obtained from the presented papers that could serve as guidelines for practical system design. Finally, various design challenges and open areas for future research are identified. [ABSTRACT FROM AUTHOR]

The availability and reliability of optical backbone links are very important to ensure the efficient operation of the Internet. To address the issue of data loss due to optical link failures, there is a need for an optimal recovery strategy so that the traffic can be rerouted on a backup path to the destination. This paper builds on top of our prior research efforts (Yavary Mehr et al., 2022; Zhou et al., 2017) which introduced the concept of Resource Delayed Release (RDR) by adding a new state called "idle state" which begins when the channel has completed carrying its services so that the next request can be carried immediately instead of waiting for a new channel to be established. While RDR improves the network performance by reducing the service provisioning time and blocking probability, it does not handle link failures which are quite common in optical networks. Therefore, enhancing RDR with protection strategies will make the network more reliable and thus we investigate this topic in this work. In this paper, we evaluate four different protection methods for single link failure recovery in WDM networks (Path Protection (PP), Partial Path Protection (PPP), Segment Protection (SegP) and Link Protection (LP)) with two different routing approaches namely Shortest Path (SPath) and Greedy (G) algorithm under uniform and non-uniform traffic generated using real traffic traces collected from a local Internet Service Provider (ISP). Special attention while evaluating these protection strategies was paid to the optimization of the amount of remaining bandwidth. The performance evaluation of the network under uniform and non-uniform traffic was done over the NSFNet and COST239 topologies by employing the metrics of link and network utilization, Blocking Probability (BP), Bandwidth Blocking Probability (BBP), Recovery Time (RT) and Service Provisioning Time (SPT). Our results show that the PPP method performs the best in terms of reducing BP, BBP, and SPT compared with PP, LP, and SegP in all three topologies while utilizing RDR. [ABSTRACT FROM AUTHOR]

Three main kinds of underwater wireless communication, which employ acoustic waves, radio frequency and optical waves, have attracted intensive research interests in recently years. Among them, the underwater optical wireless communication (UOWC) is characterized by high propagation speed and large transmission bandwidth. But, the optical waves in underwater environment are significantly affected by absorption and scattering effects, which limit their transmission range. In order to enhance the performance of UOWC, designing a transmission and energy efficiency routing algorithm has become a non-ignorable issue in UOWC. In this paper, a transmission distance adaptive dual-hop (TDAD) routing algorithm is proposed for underwater optical wireless networks (UOWNs) to improve their efficiency in packet-delivery and energy-consumption. Unlike the existing routing algorithms designed for UOWNs, which pre-set the transmission range of network nodes, the proposed TDAD algorithm adaptively selects the transmission range for each node according to the diversity of heterogeneous service requests and employs location and energy information in its dual-hop based routing procedure. Simulation results indicate that the proposed TDAD algorithm remarkably improves packet delivery rate with more balanced energy consumption when compared to the deviation angle-based single-hop (DAS) algorithm and the distributed sector-based (DS) routing algorithm. [ABSTRACT FROM AUTHOR]

The software-defined optical network (SDON) is a revolutionary approach in the field of optical networks. The separation of the control plane and data plane in software-defined networking (SDN) provides enhanced security and simplified network administration. Nevertheless, performance and control plane scalability are significant issues in SDN. SDN performance can be evaluated using parameters such as burst loss, delay, channel occupancy, packet loss, throughput, and average response time. The number of messages exchanged between the data plane and the control plane is used as a metric to determine controller scalability. As the network load increases, the controller experiences a higher flow of messages. It causes delay and burst loss in transmitting the burst. Occasionally, bursts exceed the capacity of the fixed-sized burstifier and are discarded because it takes a long time to identify a suitable route for the burst. Hence, it is essential to minimize the volume of messages exchanged between the control plane and the data plane to improve performance and controller scalability. In this paper, we propose a scalable SDN optical network architecture that minimizes the number of messages exchanged between the data plane and the control plane. We proposed mechanisms like channel reservation, transmission cycles, and guard time between cycles to enhance both the speed and the quality of burst transmission. Prior to transmission, resources or channels are allocated to bursts to minimize the possibility of burst collision and loss. The data plane comprises an optical burst switching (OBS) network, and the flow table entries are periodically updated to minimize inter-plane communication. We perform simulations to evaluate and compare the performance of the proposed architecture with the existing state-of-the-art architecture reported in the literature. The proposed architecture performs better than the existing state-of-the-art in terms of metrics including burst loss, delay, channel occupancy, packet loss, throughput, average response time, and reduction in the number of messages exchanged between the data plane and the control plane. Experimental results indicate a 41% reduction in mean burst loss probability and a 40.5% reduction in mean burst sending delay compared to existing architectures. Additionally, 42.1% fewer messages are exchanged between the control plane and the data plane compared to the number of exchanged messages in existing architectures. [ABSTRACT FROM AUTHOR]

This paper considers the optimization of wide-sense non-blocking wavelength-space-wavelength switching fabrics for elastic optical networks. Recently, wide-sense non-blocking conditions for two types of switching fabrics, named WSW1 and WSW2, have been derived and proved. In this paper, we optimize these two architectures in terms of numbers of required switching elements. Switching fabric architectures of different capacities are investigated using the full search, i.e., for each architecture and capacity, all possible configurations are checked. The results clearly present the controversy between architectures on numbers of tunable wavelength converters and their conversion range, number of input fibers and number of required bandwidth-variable wavelength selective switches. The information provided by this research can help us understand the effect of different implementation parameters, and draw more general conclusions about the parameters of optimal switching fabrics. [ABSTRACT FROM AUTHOR]

The paper considers the optimization of strict-sense nonblocking three-stage wavelength-space-wavelength switching fabrics for elastic optical switching nodes. Strict-sense nonblocking conditions for such switching fabrics have recently been presented. A brief analysis of the number of switches required to construct such fabrics was also presented in that paper. In this paper, we present a detailed estimation of the number of elements in these switching fabrics of different capacities. To find the switching fabric with the lowest number of switching elements, all possible configurations have been checked. Such an exhaustive search was possible, since the final parameters of the switching fabric of a given capacity were found within less than a minute. The results obtained for networks of several capacities allow us to draw more general conclusions about the parameters of optimal switching fabrics. [ABSTRACT FROM AUTHOR]

The paper shows the possibility to reduce energy consumption in banyan-type switching fabrics working under different control algorithms. This can be done by adopting the structure of switching fabric to the intensity of traffic offered, providing lossless operation of the switching fabric at the same time. An analytical model determining the number of planes which is required for lossless servicing the offered traffic is also presented. Results obtained from the model are compared with simulation result showing high accuracy of the proposed model. The paper demonstrates also that, when using the proposed model, the amount of saved electrical energy, consumed by a switching fabric composed of switching elements based on Mach-Zhander interferometers, starts from a few watts (for switching fabric with 64 inputs) up to 1 kW (for switching fabric with 1024 inputs). [ABSTRACT FROM AUTHOR]

Abstract FSO (Free Space Optics) is a well established wireless optical transmission technology considered as an alternative to radio communications, for example in metropolitan wireless mesh networks. An FSO link is established by means of a laser beam connecting the transmitter and the receiver placed in the line of sight. A major disadvantage of FSO links (with respect to fiber links) is their sensitivity to weather conditions such as fog, rain and snow, causing substantial loss of the transmission power over the optical channel due mostly to absorption and scattering. Thus, although the FSO technology allows for fast and low-cost deployment of broadband networks, its operation will be affected by this sensitivity, manifested by substantial losses in links' transmission capacity with respect to the nominal capacity. Therefore, a proper approach to FSO network dimensioning should take such losses into account so that the level of carried traffic is satisfactory under all observed weather conditions. In the paper we describe such an approach. We introduce a relevant dimensioning problem and present a robust optimization algorithm for such enhanced dimensioning. A substantial part of the paper is devoted to present a numerical study of two FSO network instances that illustrates the promising effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract Space division multiplexed-elastic optical networking (SDM-EON) is considered as the promising solution to overcome the capacity crunch of optical transport networks. The resource allocation problem of SDM-EON includes the route, modulation level, space, and spectrum assignment (RMLSSA). In this paper, we first investigate the effect of fiber types, switching solutions, and networking approaches on the resource allocation problem of SDM-EON, and try to consider comprehensive all-inclusive constraints. Then, a new generic formulation of switching adaptable (SA)-RMLSSA is proposed as an integer linear programing (ILP) for static traffic, based on these comprehensive constraints. In addition, the heuristic switching adaptable resource allocation (SARA) algorithm is introduced. Finally, the paper evaluates the effectiveness of SARA, with two sorting policies of connection demands, to find the near-optimal solution of different networking approaches. This evaluation is performed for parallel spectral superchannel (PS-Ch), limited spatial-spectral superchannel (LS2-Ch), group limited spatial-spectral superchannel (GLS2-Ch), and free spatial-spectral superchannel (FS2-Ch) switchings (with both ribbon and ring configurations of multi-core fibers (MCF), and having or not having spatial guardband) with operational assumptions in regard to the quality of transmission (related to the used fiber type) and traffic profile. The effect of each networking approach, having modulation adaptivity tailored for each fiber type, enabling spatial guardbands for MCFs, and cores configurations are investigated by maximum utilized frequency slot index (MUFSI) and demand utilization ratio (DUR) as metrics of static traffic. Moreover, the use of SARA for dynamic traffic is investigated for real network experiment. [ABSTRACT FROM AUTHOR]

Abstract Connection provisioning in Wavelength Division Multiplexing (WDM) networks needs to account for a number of crucial parameters. On the one hand, operators need to ensure the connection availability requirements defined in Service Level Agreements (SLAs). This is addressed by selecting an appropriate amount of backup resources and recovery strategies for the connections over which services are provisioned. Services requiring less strict availability requirements can be routed over unprotected lightpaths. Services with more strict availability requirements are provisioned over protected lightpaths in order to cope with possible failures in the network. Another important aspect to consider during the provisioning process is energy efficiency. Green strategies leverage on setting network devices in Sleep Mode (SM) or Active Mode (AM) depending on whether or not they are needed to accommodate traffic. However, frequent power state changes introduce thermal fatigue which in turn has a negative effect on the device lifetime. Finally, in multi-period traffic scenarios, it is also important to minimize the number of reconfigurations of lightpaths already established in the network in order to avoid possible traffic disruptions at higher layers. The work presented in this paper tackles the connection provisioning paradigm in an optical backbone network with a multi-period traffic scenario. More specifically the paper looks into the interplay among (i) energy efficiency, (ii) thermal fatigue, and (iii) lightpath reconfiguration aspects. To this end, the Energy and Fatigue Aware Heuristic with Unnecessary Reconfiguration Avoidance (EFAH-URA) is introduced, showing that it is possible to balance the three aspects mentioned above in an efficient way. When compared to the pure energy-aware strategies, EFAH-URA significantly improves the average connection availability for both unprotected and protected connections. On the other hand, it is done at the expense of reduced energy saving. [ABSTRACT FROM AUTHOR]

Abstract Metropolitan area networks are currently challenged by a sharp increase of peak traffic demands, and would thus benefit from flexible network mechanisms able to ensure excellent Quality of Service (QoS) while limiting costs. In this paper, we evaluate the gain in Capital and Operational Expenditures (CAPEX and OPEX) brought by Time-domain Wavelength Interleaved Network (TWIN) thanks to a dynamic control plane implemented in a Software Defined Network (SDN) framework. The SDN compliant TWIN control plane attributes resources and activates the transmitters (Tx), receivers (Rx) and transceivers (TRx) according to traffic variations. The present paper first recaps how to dimension TWIN in terms of Tx, Rx or TRx to support a given traffic matrix. It is then shown that 20% resource over-provisioning allows to meet the metro level QoS requirements set by the Metro Ethernet Forum (MEF). Then, taking into account this over-provisioning value, a comparative study, assessing the OPEX and CAPEX savings for different configuration periods' duration (varying between 5 min and 6 h) is carried out. The obtained results show that the dynamic network re-configuration approach can bring some CAPEX savings and highly significant OPEX savings in a realistic metropolitan network scenario, even for rather large configuration periods (e.g. 1 h). Finally, using a control plane based on this configuration period, the CAPEX and OPEX for TWIN are compared with those for the current Optical Circuit Switching (OCS) transport technologies (both opaque and transparent). It is shown that TWIN CAPEX/OPEX savings are important even if the TWIN's Tx/Rx/TRx unit expenditure cost is many times more expensive than that of OCS. [ABSTRACT FROM AUTHOR]

C-RAN is an architecture for future 5G cellular networks, which has the potential of combining emerging technologies from both the wireless and the Information Technology (IT) industries by incorporating cloud computing into Radio Access Networks (RANs). This paper presents a comprehensive review of the transport options for constructing mobile fronthaul, capable of supporting applications and services beyond LTE advanced. The architecture of C-RAN is first studied which comprises mobile backhaul, mobile fronthaul and the User Equipment (UE). Then, it describes the different fronthaul transport options that are capable to the drastic increase of wireless bandwidth as well as the massive deployment of small cells. It also numerically evaluated the End to End (E2E) latency, the maximum possible separation distance between Remote Radio Head (RRH) and Base Band Unit (BBU), and Packet Delay Variation (PDV) of the mobile fronthaul solutions with emphasis on Ethernet network. Moreover, the paper explains Ethernet frame format for transporting Radio over Ethernet (RoE) traffic. Finally, the paper presents a summary of emerging research directions, opportunities and challenges in optical networking in mobile fronthual networks. [ABSTRACT FROM AUTHOR]

This paper proposes a routing and wavelength assignment (RWA) scheme that considers full optical carrier replication to minimize the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. Unlike the conventional wavelength division multiplexing networks where each node contains multiple laser diodes, the WRMD networks use a light source, called the multi-carrier light source, to ease the difficulty of controlling many light source devices. The optical carrier replication at any node of optical carrier or any end node of lightpath, called full optical carrier replication, improves the performance of the conventional schemes, which do not consider full optical carrier replication. This paper first formulates the RWA problem considering full optical carrier replication as an integer linear programming problem that minimizes the number of required wavelengths to satisfy the given lightpath setup requests. A heuristic RWA scheme is then proposed to solve the RWA problem in practical times. Simulation results show that our proposed heuristic RWA scheme for the WRMD network achieves a near-optimum number of wavelengths. In addition, it is able to reduce the number of required wavelengths for lightpath establishment, compared to the conventional scheme. [ABSTRACT FROM AUTHOR]

Artificial intelligence (AI) is an extensive scientific discipline which enables computer systems to solve problems by emulating complex biological processes such as learning, reasoning and self-correction. This paper presents a comprehensive review of the application of AI techniques for improving performance of optical communication systems and networks. The use of AI-based techniques is first studied in applications related to optical transmission, ranging from the characterization and operation of network components to performance monitoring, mitigation of nonlinearities, and quality of transmission estimation. Then, applications related to optical network control and management are also reviewed, including topics like optical network planning and operation in both transport and access networks. Finally, the paper also presents a summary of opportunities and challenges in optical networking where AI is expected to play a key role in the near future. [ABSTRACT FROM AUTHOR]

Optical Packet Switched (OPS) technology is under study as a promising solution for addressing the rapid growth of network-intensive applications having different Quality of Service (QoS) requirements. By employing Optical Circuit Switched (OCS) networks, an optimized Packet Loss Ratio (PLR), delay and Packet Delay Variation (PDV) performance can be obtained. It is, however, very demanding to offer a QoS comparable to OCS network through the OPS network in order to support a significant and growing number of applications. Thus, moving from OCS to OPS network, QoS is a critical issue. Hence, this paper analyzes the QoS requirements of network-intensive applications and services. Moreover, the paper derived an expression for performance metrics of a single OPS switch and ring OPS network. It is found that the International Telecommunication Union - Telecommunication (ITU-T) classification is extended with the new requirements of applications and services. For example, the upper bound delay, PDV and PLR of video streaming requires (100 ms, 400 ms), 50 ms and 1 E − 05 respectively. In this work, these values are improved as delay within 10 ms, PDV in micro seconds and PLR of 1 E − 07 at full load. It is also shown that a Fixed Delay Line (FDL) has to be considered when low PLR is required and when PDV and delay are not critical issues. [ABSTRACT FROM AUTHOR]

Based on multi-standard OLT management structure, this paper realizes supporting GPON and EPON simultaneously in metro-access optical network. To adjust VPON structure dynamically, virtual access mechanism is established. To support two different standards, compatible multi-standard management structure for VPONs is proposed. It can also manage dynamic connection between ONU and OLT. To transmit GPON and EPON frames in the same wavelength, this paper proposes shared bandwidth algorithm to allocate bandwidth to GPON and EPON sub-networks fairly. This algorithm can prevent bandwidth monopoly from high load sub-network, when load of one sub-network is much higher than that of the other. To further balance QoS demands for ONUs, different class services will acquire bandwidth by priority. Finally, the simulation results demonstrate a good performance of the mechanism and algorithm. [ABSTRACT FROM AUTHOR]

In the paper we introduce an optimization framework for traffic restoration in optical wireless networks. As such networks experience multiple partial link failures, we introduce a generic extension of restoration strategies developed for wired networks (that assume total link failures) which enables handling partial link failures as well. The particular traffic restoration strategy studied in the paper combines a known rerouting method for total link failures (Restricted Restoration – RR) and a recently developed restoration method for partial failures (Flow Thinning – FT). The paper presents a generic optimization model for link dimensioning for arbitrary sets of failure states, and its specific version that assumes the above described RR/FT strategy. For the RR/FT case, an exact solution method based on path generation is described, together with numerical results illustrating its efficiency. Next, the paper describes how the generic optimization model can be used for the FSO networks. The specific features of the failures observed in such networks (FSO is highly sensitive to atmospheric conditions) imply the necessity of treating the dimensioning problem in its chance constrained programming version which is NP -hard by its very nature. For that we have developed an iterative heuristic scheme that makes use of the exact solution method developed for the generic case. Numerical results illustrating the so-obtained robust solutions of the dimensioning problem are also reported. [ABSTRACT FROM AUTHOR]

10-Gigabit passive optical network (XG-PON) has emerged as an effective architecture to meet today's growing demand for bandwidth in the family of next-generation passive optical networks (NG-PON). It supports various quality of services such as voice, video live streaming, network browsing, etc., where these services demand bandwidth, which is limited. To overcome this limitation, bandwidth management schemes are employed by central authorities such as optical line terminals (OLT). Several dynamic bandwidth allocation (DBA) schemes exist for XG-PON in the literature, but these lack in detailed information about XG-PON and a comparison of various DBA schemes in one place. Therefore, this paper presents a detailed architecture of XG-PON and comprehensively reviews the existing dynamic bandwidth allocation schemes for the XG-PON system. This paper further identifies and implements majorly adopted bandwidth allocation schemes such as GIANT, X-GIANT, IACG, and EBU using a pre-existing module of XG-PON in the network simulator 3 (NS-3) simulation framework. The results have been obtained in two phases having different traffic scenarios, where, in phase 1, the load of all ONUs has been increased simultaneously, and in phase 2, the load of only one ONU has been increased. The obtained results have been analysed in terms of various network performance metrics. Hence, this paper reviews the available DBA schemes and provides a comprehensive analysis of the identified important DBA schemes. [ABSTRACT FROM AUTHOR]

In this paper we extended the well known conditions for strict-sense nonblocking operation of the three-stage Clos switching network to the case in which k multiplexing levels (called later in this paper as k degrees of freedom) are used on input, output, and interstage links. Up till now only the cases with one multiplexing level were considered in the literature—time-division or wavelength-division. Current research shows that transmission systems with many multiplexing levels will be used in the future to increase available transmission speed in telecommunication networks. There will be also a need for switching connecting paths going through such multiplexed links in large capacity optical cross-connect systems, routers, or data center networks. In this paper we proved the strict-sense nonblocking conditions for the three-stage Clos network with k degrees of freedom. We also analyzed the cost of switching fabrics of selected capacities and with three degrees of freedom in terms of the required number of elements. [ABSTRACT FROM AUTHOR]

In space division multiplexing-elastic optical networks (SDM-EONs), crosstalk and fragmentation are the significant factors determining overall resource utilization. Crosstalk and fragmentation management spectral resource allocation schemes can enhance the overall resource utilization in SDM-EONs. This paper proposes three crosstalk and fragmentation management bi-directional resource allocation schemes for multi-core SDM-EONs to suppress inter-core crosstalk and network fragmentation. A spatial resource partitioning method is presented to mitigate inter-core crosstalk, and this paper adopts a k-shortest path routing method to suppress fragmentation while spectral resource allocation. To the best of our knowledge, there is no such scheme that handles both crosstalk and fragmentation together while allocating spectral resources in a counter-propagating manner for multi-core fiber (MCF) SDM-EONs. The estimated result shows that the proposed scheme outperforms the traditional co-propagation method and enhances existing resource utilization by reducing blocked requests. [ABSTRACT FROM AUTHOR]

For the mixed-line-rate (MLR) wavelength-division multiplexing (WDM) networks, each wavelength of fiber can provide different transmitting rates (in 10/40/100 Gbps) by using different modulation types. Since the MLR-WDM is becoming the key and a cost-efficient technique for the network upgrading, the problem for constructing an efficient virtual topology becomes an important issue. In this paper, the Virtual Topology Design ( VTD ) problem on MLR-WDM network is considered. Given the physical backbone network and traffic demand matrix between nodes of the network, the goal of the VTD problem is to determine which node-pairs to be connected by establishing lightpaths, the actual routes of the lightpaths, the transmitting rates of lightpaths, and the assigned wavelengths of lightpaths such that the total cost of deployed transceivers can be minimized. Since the VTD problem on MLR-WDM network is a hard problem, in the paper, a heuristic algorithm (HA) and a genetic algorithm ( GA ) are proposed to solve it. Experimental results indicate that the proposed GA is robust for this problem. [ABSTRACT FROM AUTHOR]

This paper proposes a routing and wavelength assignment (RWA) scheme that supports multiple light-source nodes to minimize the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks use a light source, called the multi-carrier light source (MCLS), to ease the difficulty of controlling many light source devices. Moreover, they are able to reuse optical carriers for improving the effectiveness of wavelength usage. Since the WRMD network suffers constraints different from those of the conventional wavelength division multiplexing (WDM) network, an RWA scheme for the WRMD network with a single light source was recently developed. To use the resources of large-scale networks efficiently, there may be a need to have more than one MCLS node. In this paper, we first formulate the RWA problem as the integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given lightpath setup requests. A heuristic RWA scheme is then introduced to solve the RWA problem in practical times. Simulation results show that the proposed heuristic RWA scheme for the WRMD network achieves a near-optimum number of wavelengths. In addition, optimizing MCLS node location is shown to reduce the number of required wavelengths for lightpath establishment. [ABSTRACT FROM AUTHOR]

This paper addresses the effect of latency optimization in large scale Data Vortex optical networks. A recently proposed strategy for path synchronization in Data Vortex networks allows for dramatic reduction of the physical delay. In particular, it can be shown that such optimization brings critical improvement to latency in large scale networks. In addition, several network enhancement techniques with additional resource have been proposed to reduce the routing hops and allows for overall better throughput. This paper explores the combination of both south-path-delay-optimization and enhancement techniques and provides a thorough examination of network performance in physical latency and throughput. As a result, a highly loaded network up to 10,000 I/O ports can maintain very small physical latency (<15 packet slots) under such optimization and enhancement. The throughput performance can be independently controlled by its redundant condition, but nearly 100% injection rate can be supported as long as the network redundancy is sufficient. The compromise between cost and performance should be taken into account. The results show that these recent development makes large scale Data Vortex networks much more feasible and can be easily adapted to support high performance computing and communication applications. [ABSTRACT FROM AUTHOR]

This paper proposes a routing and wavelength assignment (RWA) scheme that minimizes the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks have two unique features. First, only one light source, called the multi-carrier light source (MCLS), is required, which eases the difficulty of controlling many light source devices. Second, optical carriers are reused to improve the efficiency of wavelength usage. Since there are differences between the WRMD network and the conventional network, an efficient RWA scheme for the WRMD network is needed for wavelength-resource-efficient lightpath establishment. To realize efficient wavelength usage, we first formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given requests. For large-scale networks, the ILP approach is not practical solution times. A heuristic RWA scheme is introduced in this paper to solve the RWA problem. Simulation results show that the proposed heuristic scheme with two carrier regenerations for the WRMD network approaches the near-optimum number of wavelengths. In addition, the optimum placement of the MCLS node is shown to reduce the number of required wavelengths for lightpath establishment, and achieve the optimum number of wavelengths. [ABSTRACT FROM AUTHOR]

Development of 5G/F5G technology leads to massive applications accessing to backbone networks, which requires the backbone networks to be upgraded. Semi-filterless elastic optical network (semi-FEON) is a suitable technology to cheaply and gradually upgrade backbone networks. In semi-FEON, routing, modulation and spectrum assignment (RMSA) problem is one of the key issues. In this paper, we study the dynamic RMSA problem in semi-FEON and propose an RMSA algorithm. The algorithm includes three innovations: a K-shortest-subnet-paths (KSSP) algorithm is designed to search candidate paths in semi-FEON, a load-balancing-least-resources (LBLR) policy is introduced to re-sort the candidate paths, and a maximum-occupied-neighbors (MON) rule is proposed to assign spectrum resources to connection requests in semi-FEON. Simulation results show that the proposed KSSP-LBLR-MON algorithm outperforms the existing works in term of bandwidth blocking probability. Concretely, the improvement ratio is greater than 59.98% and 66.64% in German-Net and Henan-Net, respectively. [ABSTRACT FROM AUTHOR]

Space-division multiplexed elastic optical networks (SDM-EONs) utilizing multi-core fiber (MCF) have been considered to address the growing traffic demand in transport networks. The quality of transmission (QoT) of MCF-based SDM-EONs is affected by inter-core and intra-core physical layer impairments (PLIs). This paper proposes an inter-core crosstalk-aware and intra-core impairment-aware algorithm for modulation, core, and spectrum assignment (CIA-MCSA) in MCF-based SDM-EONs. The CIA-MCSA considers PLI estimation in a dynamic traffic scenario and allocates new lightpaths using strategies to avoid blocking by insufficient QoT of the new lightpath and of already active lightpaths. Using numerical simulation, the performance of the CIA-MCSA is compared with five algorithms proposed by other authors, considering two distinct network topologies, heterogeneous traffic demands, and different levels of inter-core crosstalk. The results show that, when compared with the most competitive of the other algorithms, (i) CIA-MCSA achieves an average reduction of the request blocking probability by at least 33.87%; (i i) CIA-MCSA achieves an average reduction of the bandwidth blocking probability by at least 20.74%; and (i i i) CIA-MCSA increases the network spectrum utilization by at least 3.04%. [ABSTRACT FROM AUTHOR]

In this paper a novel algorithm with delay guarantees for high priority traffic based on a Proportional (P) controller for Long-Reach Passive Optical Networks (LR-PONs) is proposed. We have recently demonstrated that Proportional--Integral--Derivative (PID) controllers are quite effective when controlling guaranteed bandwidth levels and in this paper this functionality is adapted to jointly deal with Class of Service (CoS) and client differentiation in order to fulfill delay requirements. Therefore, it leads to an efficient control of the mean packet delay which enhances the provided Quality of Service (QoS) inside the LR-PON. Simulation results have exhibited that the bandwidth allocation process made by the P controller achieves this objective faster than other existing proposals. In fact, it stabilizes the priority delays in less than 2 min comparing with 5 or 6 min obtained by other proposals. Furthermore, it has been demonstrated that its performance is more robust than other proposals since it is independent of the initial network conditions, adapting very efficiently the available resources in order to comply with the established delay bounds of the most restrictive services. [ABSTRACT FROM AUTHOR]

Abstract: This paper serves as a tutorial lecture on the use of network coding to provide resource efficient and agile proactive protection. Network coding, which was introduced in Ahlswede et al. (2000) [1], allows intermediate network nodes to form linear combinations of packets received on different input links. The use of network coding results in capacity enhancement. This capacity enhancement is used to provide protection channels which are used to carry combinations of redundant data, and are solved by the receivers in order to recover data lost due to network failures. The paper starts by addressing network coding-based protection of bidirectional unicast connections, and explains the use of p-Cycles to carry linear combinations of the redundant data units. The paper also discusses an earlier protection strategy which is based on diversity coding, in which the linear combinations are formed at special nodes, including sources, and is used to protect unidirectional connections. A generalized network coding-based protection which uses a tree to carry the linear combinations will be presented. Protection of multicast connections using network coding is also explained. [Copyright &y& Elsevier]

Abstract: Long-Reach Passive Optical Network (LR-PON) is known as a promising and economical solution for Next-Generation PON (NG-PON). Survivability is one of the key issues in the planning of LR-PON because massive high-rate traffic flows may be interrupted in case of network component failure. However, the survivability issue for LR-PON is addressed in little works. More importantly, most of the previous works focus on single distribution fiber failure and remain untouched the simultaneous failure of multiple distribution fibers, which is a possible failure scenario in LR-PON. In this paper, we focus on the survivability of LR-PON against single Shared-Risk Link Group (SRLG) failure. A reliability model is proposed to represent the disconnection probability of the ONUs. Based on this reliability model, we propose a novel Backup Fibers Protection (BFP) scheme. In the BFP scheme, we deal with the optimization problem of allocating backup capacity and deploying backup fibers. Under the constraint of reliability requirement, our objective is to fully protect all traffic demand in the network with the minimum deployment cost of backup fibers. Both ILP-based approach and heuristic approach are proposed to solve the optimization problem in the BFP scheme. To the best of our knowledge, this paper is the first work regarding the survivability of LR-PON against single SRLG failure. Through extensive simulation, we investigate the performance of BFP and demonstrate its effectiveness in different scenarios. [Copyright &y& Elsevier]

Abstract: Cloud computing, building on the idea of “computation as a public utility” is made possible by the increased network capabilities in terms of bandwidth and reduced latency. The cloud paradigm today sees adoption in many businesses given its advantages, not only from a customer point of view (e.g., universal access to the same applications across all company branches) but also from the application provider and network operator perspective (e.g., software updates no longer need to be distributed). To be able to offer cloud computing services efficiently, service providers need not just an infrastructure comprising both network and IT resources, but especially a control system that is able to orchestrate such integrated network and IT services. This paper offers a new proposal for such a system: an enhanced network control plane, the NCP+, which is based on a GMPLS control plane with a Hierarchical Path Computation Element (PCE) architecture able to jointly make network routing and IT server provisioning decisions. Indeed, in the assumed cloud paradigm, a user generally does not care what exact server the offered service is using, as long as its service requirements are met: thus the anycast principle applies. The paper discusses (i) the architecture of the NCP+, (ii) two IT-aware aggregation mechanisms to be used in the hierarchical PCE approach and (iii) routing and scheduling algorithms for those aggregation mechanisms. We conclude this work with a thorough simulation analysis of the aggregation and routing/scheduling policies showing that Full Mesh aggregation where the domain topology is represented by a complete graph, although being less scalable in terms of computation time, is able to provision efficiently using the proposed load balancing routing and scheduling policy. However, for a scenario with stringent IT requirements, Star could be used in parallel for scenarios where end-to-end setup times are important. [Copyright &y& Elsevier]

Abstract: Although having high potential for broadband wireless access, wireless mesh networks are known to suffer from throughput and fairness problems, and are thus hard to scale to large size. To this end, hierarchical architectures provide a solution to this scalability problem. In this paper, we address the problem of design and optimization of a tiered wireless access network that exploits free space optical (FSO) communications. The lower tier consists of mesh routers that are clustered based on traffic demands and delay requirements. The cluster heads are equipped with wireless optical transceivers and form the upper tier FSO network. For topology design and optimization, we first present a plane sweeping and clustering (PSC) algorithm aiming to minimize the total number of clusters. PSC sweeps the network area and captures cluster members under delay and traffic load constraints. For the upper tier FSO network, we present an algebraic connectivity-based formulation for topology optimization. We then develop a greedy edge-appending (GEA) algorithm, as well as its distributed version, that iteratively inserts edges to maximize algebraic connectivity. The proposed algorithms are analyzed and evaluated via simulations, and are shown to be highly effective as compared to the performance bounds derived in this paper. [Copyright &y& Elsevier]

In today's wide area networks, especially in Optical Transport Networks (OTN) with Software Defined Networking (SDN) features enabled over Wavelength Division Multiplexing (WDM), Bandwidth on Demand (BoD) is an important service that can be satisfied by dynamic end-to-end service provisioning. Service provisioning time (SPT) and Blocking Probability (BP) are critical performance metrics for the users and carriers. This paper extends the concept of the Resource Delayed Release (RDR) strategy for WDM networks. The basic idea of this strategy is to introduce a delay in releasing the optical channel, when the channel is no longer carrying any services. This delay can help speed up the provisioning time for carrying the next service request, avoiding the time usually taken to establish a new optical channel. The main goals of the RDR method are to reduce SPT and BP while simultaneously satisfying the quality of service (QoS) constraints. In this paper, we investigate the effects of uniform and non-uniform traffic on the performance of RDR strategy. For non-uniform traffic simulation, we use a mesh topology with the 14 most populous cities in USA as of 2018 and model the non-uniform traffic based on population density. Further, we introduce a new metric called the Bandwidth Blocking Probability (BBP) to measure the quality of the service offered by the network. Simulation results show advantages of using the RDR method under a wide variety of traffic scenarios for both uniform and non-uniform traffic distributions compared to the traditional method. RDR reduces SPT by 45–90% for uniform traffic and 41–75% for non-uniform traffic. RDR reduces BP by 35–85% for uniform traffic and 30–75% for non-uniform traffic. Additionally, RDR lowers BBP by 31–73% for uniform traffic and 29–68% for non-uniform traffic. [ABSTRACT FROM AUTHOR]

In the last twenty years, optical networks have witnessed recurrent changes in their management and control architecture. In this paper, we present a historical timeline and a future perspective of the evolution of optical network management and control deployed for Wavelength Switched Optical Networks (WSON), Elastic Optical Networks (EON) and (multilayer) Data Center Networks. Early implementations of WSON envisaged a static and centralized provisioning approach supported by the Management Plane only. Gradually, the requirement of accommodating more network dynamicity in WSON, and later in EON, pushed the adoption of a distributed control, mostly supported by vendor-dependent implementations of the Generalized MultiProtocol Label Switching (GMPLS) protocol suite. The drawbacks of the fully distributed GMPLS-based control, such as resource contention, suboptimal resource usage, and complex computations (e.g., to account for physical layer constraints) showed the necessity to bring back some of the routing/provisioning functions to a centralized Path Computation Element (PCE) capable of accounting for e.g. physical impairments and interworking with GMPLS. The centralized control then gained its momentum and brought a radical change in network control, through the separation of data and control plane introduced by the paradigm of Software Defined Networking (SDN). Such an approach has been gradually extended to optical network control. The paper, eventually, presents the most advanced control techniques, namely the intent-based networking, the observe/decide/act state-based approach providing for autonomic optical network and the (closed-loop) zero-touch service management approach. Advanced traffic conditioning techniques are also detailed, namely the in-band telemetry and the exploitation of Programming Protocol-Independent Packet Processors (P4) language capabilities as well as solutions tailored for data center networks: all of them are still in a research stage and to be integrated within future optical network architectures. [ABSTRACT FROM AUTHOR]

The survivable logical topology mapping (SLTM) problem in IP-over-WDM networks is to map each link in the logical topology (IP layer) onto a lightpath in the physical topology (optical layer) such that a failure of a physical link does not cause the logical topology to become disconnected. This problem is known to be NP-complete. For this SLTM problem, two lines of investigations have been reported in the literature: the mathematical programming approach [1] and the structural approach introduced by Kurant and Thiran in [2] and pursued by Thulasiraman et al. [3,4,5]. In this paper we present an integrated treatment of the theoretical foundation of the survivable topology mapping problem presented in [3,4,5]. We believe that the algorithmic strategy developed in this paper will serve as an important phase in any strategy in the emerging area of resilient slicing of elastic optical networks. We conclude with a comparative evaluation, based on simulations, of the different algorithmic strategies developed in the paper, and also pointing to applications beyond IP-over-WDM optical networks, in particular, survivable design of inter-dependent multi-layer cyber physical systems such as smart power grids. [ABSTRACT FROM AUTHOR]

Elastic optical networks (EONs) are a promising solution for future high-speed optical communication, and multicasting in EONs can efficiently support many emerging services. Different schemes, such as path, tree and subtree schemes, serve multicast services. In this paper, we consider a three-stage wavelength-space-wavelength (WSW) node architecture, which adopts wavelength switches in the first and last stages and space switches in the middle stage, and uses the path scheme to accommodate multicast requests, as proposed in an earlier work for elastic optical networks. We also enhance the WSW architecture to serve multicast requests in a more spectrum-efficient way, namely, using the subtree scheme, by making each switch support multicast capacity, and we term the resulting architecture M-WSW. To the best of our knowledge, this is the first study of the WSW architecture using the subtree scheme to support multicast capacity. We prove the sufficient and necessary conditions, in terms of the number of middle switches, of the M-WSW architecture for being strictly nonblocking (SNB) and wide-sense nonblocking (WSNB) under the two routing algorithms proposed in this paper. Our results show that the number of middle switches required for the architecture to be WSNB under each of the two proposed routing algorithms is much less than the number of middle switches required for SNB, especially when the SNB results meet the boundary condition. [ABSTRACT FROM AUTHOR]

Abstract: This paper considers digital video transport over Optical Burst Switched networks where burst losses cause data loss from one or more adjacent video frames. Analytical approximations for the frame losses and video playback interruptions are derived and validated using simulations. Both parameters require a very limited and static amount of data about the video on the user side and some quality of service metrics about the network to quantify the quality of the received video. The results take into account the strong dependency in the video traffic structure due to the coding mechanisms. The critical effect of video coding parameters is also revealed. The paper also presents a Traffic Engineering procedure to select the best parameters for the edge node and the video codec to meet a given video quality level on the user side. [Copyright &y& Elsevier]

Abstract: Long Reach PONs (LR-PON) were proposed to extend the benefits of Passive Optical Networks (PON) to more users and to a larger area. This paper considers a Dynamic Bandwidth Allocation (DBA) based on a hybrid combination of Time Division Multiplexing (TDM) and Wavelength Division Multiplexing (WDM). The time complexity of the DBA algorithm is typically O(n log n), where n denotes the number of ONUs. Since the maximum number of supported ONUs in an LR-PON can be as high as 2048, the computation time required for computing a schedule will be very high and directly impacts the overall network performance. In this paper, we have presented a grouping strategy to reduce the computation requirements. The number of ONUs is split into mutually exclusive groups with the OLT scheduling each group independently and in parallel. With the static grouping strategy every user is assigned to a group and the assignment of wavelength resources is fixed. However, with non-uniform loads, we observed that static grouping was not found to be suitable as the delay variation was significant across the groups. To address this gap, we introduce the concept of dynamic grouping and define three dynamic grouping heuristics that adapt to the current network load conditions and (re)allocate the ONUs and wavelength resources suitably. The proposed schemes have been compared in terms of delay variation and wavelength utilization. Of the three heuristics, ONU to Least Loaded wavelength group (OLL) and Least Wavelength Resources (LWR) heuristics balance the packet delay across ONUs assigned to different groups and Proportional Wavelength Usage (PWU) heuristic reduces power consumption by allocating fewer wavelength resources. [Copyright &y& Elsevier]

Abstract: This paper focuses on the survivable routing problem in WDM mesh networks where the objective is to minimize the total number of wavelengths used for establishing working and protection paths in the WDM networks. The past studies for survivable routing suffers from the scalability problem when the number of nodes/links or connection requests grows in the network. In this paper, a novel path-based shared protection framework, namely inter group shared protection (I-GSP), is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. Optimization is performed on these PGs such that sharing of protection wavelengths is considered not only inside a PG, but between the PGs. Simulation results show that I-GSP based integer linear programming model, namely, ILP-II solves the networks in a reasonable amount of time for which a regular integer linear programming formulation, namely, ILP-I becomes computationally intractable. For most of the cases the gap between the optimal solution and the ILP-II stays within 6%. The proposed ILP-II model yields a scalable solution for the capacity planning in the survivable optical networks based on the proposed I-GSP protection architecture. [Copyright &y& Elsevier]

Abstract: FAST TCP is important for promoting data-intensive applications since it can cleverly react to both packet loss and delay for detecting network congestion. This paper provides a continuous time model and extensive stability analysis of FAST TCP congestion-control mechanism in bufferless Optical Burst Switched Networks (OBS). The paper first shows that random burst contentions are essential to stabilize the network, but cause throughput degradation in FAST TCP flows when a burst with all the packets from a single round is dropped. Second, it shows that FAST TCP is vulnerable to burst delay and fails to detect network congestion due to the little variation of round-trip time, thus unstable. Finally it shows that introducing extra delays by implementing burst retransmission stabilizes FAST TCP over OBS. The paper proves that FAST TCP is not stable over barebone OBS. However, it is locally, exponentially, and asymptotically stable over OBS with burst retransmission. [Copyright &y& Elsevier]

Abstract: This paper analyzes destination initiated reservation for Generalized Multi-Protocol Label Switching (GMPLS) based wavelength division multiplexing (WDM) networks and determines, via simulation, probabilities of both forward blocking and backward blocking. During light traffic load, any degradation in performance is due to backward blocking, whereas during heavy traffic load forward blocking dominates. In order to minimize performance degradation due to blocking, this paper proposes a token based routing scheme that is capable of searching for the availability of more than one route from source to destination, meeting the desired quality of service (QoS). Extensive simulation results show that the proposed technique significantly improves the blocking performance and setup delay. [Copyright &y& Elsevier]

The most effective way of providing popular user services such as high-definition television, video conferencing and distributed gaming over the Internet is multicasting. Protecting multicast sessions against single link failure or a fiber cut in the WDM optical backbone is thus vital. Protection schemes involve reserving resources for backup paths that remain idle during normal fault-free operation. It is thus important to design protection or survivability schemes that consume as few extra resources as possible. A number of protection schemes for multicast sessions exist in the literature but only few can provide rapid recovery. In this paper we propose a new offline strategy for ensuring survivability of multicast traffic that can aid rapid recovery from a link failure. Our strategy is designed to achieve significant resource saving while providing recovery speed comparable to 1:1 dedicated path protection. We first propose an Integer Linear Program formulation to solve the problem optimally for small networks and then a heuristic for large networks. Performance comparisons show that our heuristic performs better than two well-known heuristics and also produces near optimal results. Time complexity analysis further shows that our heuristic runs in polynomial time. [ABSTRACT FROM AUTHOR]