Dedicated Path Protection Research Articles

Dedicated Path Protection with Flexible Switching Selection in Passive Optical 5G Xhaul Access Networks

This work addresses the optimized planning of survivable optical 5G Xhaul access networks employing passive Wavelength Division Multiplexing (WDM) technologies. Specifically, it focuses on the reliability of optical transmission paths connecting remote radio sites to a central hub ensured by using a novel, cost-effective, flexible, and dedicated path protection (DPP-F) scheme, protecting against single-link failures. The proposed DPP-F network protection approach allows for switching of individual wavelengths or the complete multiplexed WDM signal, flexibly applying the best switching option according to given traffic demands. Concurrently, it enables traffic aggregation on the transmission paths from the end and intermediate nodes to minimize the overall network deployment cost. The problem of selecting primary (working) and backup (protection) paths, together with the selection of the best switching and traffic aggregation options, is modeled and solved as a mixed-integer linear programming (MILP) optimization problem. To evaluate the cost savings achieved with DPP-F, we compare it with two reference DPP schemes based on switching the entire multiplexed WDM signal (DPP-M) and individual wavelengths (DPP-W). Numerical experiments conducted across a wide range of network scenarios reveal, among other things, that DPP-F’s performance is at least as good as that of the reference methods, bringing significant cost savings (from several to tens of percent) in most of the analyzed network scenarios.

Reliable Provisioning With Degraded Service Using Multipath Routing From Multiple Data Centers in Optical Metro Networks

With the adoption of edge computing, several data centers are available within the footprint of an optical metro network, and contents are replicated in multiple locations. Such a wide content replication offers a unique opportunity to provide better services to users, especially for content-based services, e.g., video delivery. Thus, a service-provisioning scheme can embrace this opportunity to optimize network resource utilization, improve reliability, and achieve lower latency. In this study, we propose a reliable service-provisioning scheme that selects the optimal subset of data centers hosting the desired content and inversely multiplexes a content request over multiple link-disjoint paths. We formulate an integer linear program and develop heuristics for the problem, and use them to solve various complex and realistic network instances. Numerical data show that, compared to conventional service-provisioning schemes such as multipath routing from a single data center or dedicated-path protection, our proposed scheme efficiently utilizes network resources, improves reliability, and reduces latency; hence, it is suitable for the above-mentioned services.

Dedicated Path Protection With Wavelength Aggregation in 5G Packet-Optical Xhaul Access Networks

Packet-optical xHaul transport networks are a promising solution for assuring low-cost connectivity between a large number of antennas, located at remote sites, and a central site (hub), in which traffic is gathered and baseband processing is performed, in dense 5G radio access networks (RANs). The demand for fiber connections in such networks can be reduced by means of optical add-drop multiplexers (OADMs), which allow to aggregate traffic from a number of remote sites onto a single optical transmission path. An important issue here is the protection of transmission paths since the failure of a single link may result in the loss of connectivity of a number of antennas. In this work, we focus on the problem of planning a survivable 5G packet-optical xHaul access network, in which the remote sites are connected with the hub by means of disjoint primary-backup paths. The network scenario is based on a passive wavelength division multiplexing (WDM) system in which the maximum transmission distance depends on the number of OADMs installed on the transmission path. In the solution proposed, network survivability is achieved using a dedicated path protection with wavelength aggregation (DPPWA) mechanism. The network planning problem is modeled and solved as an integer linear programming (ILP) problem. Numerical results indicate, among others, that cost savings of between 20%–40% can be achieved in lower traffic load scenarios due to the traffic aggregation by means of OADMs, and that the savings increase with the cost of dark fiber lease.

Protection by diversity in elastic optical networks subject to single link failure

Among the multipath protection schemes found in the literature, the Partitioning Dedicated Path Protection — PDPP proposes to divide the total transmission rate required by the connection in equal parts, and then proceed the transmission of each part using multiple disjoint paths. Nevertheless, it is also possible to partition the transmission rate unequally among paths, enabling benefits to network performance. This article proposes a mixed-integer linear programming (MILP) formulation to find an optimized unequally partitioning of connections’ transmission rate among multiple disjoint paths, in order to provide dedicated protection and reduction in maximum number of slots on network and average bandwidth squeezing. The solution is analysed over a number of realistic networks, showing that the proposed formulation significantly reduces the spectral usage compared to traditional protection mechanisms and reduces the amount of squeezing required compared to the former PDPP approach.

The Trade-Offs between Optimality and Feasibility in Online Routing with Dedicated Path Protection in Elastic Optical Networks.

The article discusses an online problem of routing and spectrum allocation with dedicated path protection in elastic optical networks. We propose three novel algorithms to solve this problem. The first of them is the minimum-cost–maximum-flow heuristic algorithm, which calculates the solution assuming that the spectrum units on the working and dedicated backup path are the same. Such an assumption, on the one hand, increases the bandwidth blocking probability; however, on the other hand, it enables a simple, cheap and fast way to connect customers to the network during the implementation phase of elastic optical networks. The next two algorithms, which determine the exact solutions, are based on the branch and bound method. The first calculates the working and dedicated backup paths with the minimum total occupied bandwidth, called the total cost, while the second calculates the paths with the minimum total length. These algorithms enable the performance evaluation of the proposed heuristic algorithm and provide the answer as to what should be optimized, the total cost or the total length of paths, in order to minimize the bandwidth blocking probability. Extensive simulation research has shown that the proposed heuristic algorithm can be used in elastic optical networks, but with a small network load. Moreover, it is shown that the optimization of the total cost of paths provides a slightly lower blocking probability than the optimization of the total length of paths.

Protection against failure of machine-learning-based QoT prediction

Machine learning (ML)-based methods are being widely explored to predict the quality of transmission (QoT) of a lightpath. They are expected to reduce the signal-to-noise ratio margin reserved for the lightpath, thus improving the spectrum efficiency of an optical network. However, many studies on this prediction are often based on synthetic datasets or datasets obtained from laboratories. As such, these datasets may not accurately represent the entire state space of a practical optical network, which is exposed in harsh environments. There are risks of failure when using these ML-based QoT prediction models. Thus, it is necessary to develop a mechanism that can guarantee the reliability of lightpath service even if the prediction model fails. For this scenario, we propose to employ the conventional network protection techniques that are usually implemented to protect against network node/link failures to also protect against the failure of QoT prediction. Based on the two representative protection techniques, i.e., 1 + 1 dedicated path protection and shared backup path protection (SBPP), the performance of the proposed protection mechanism is evaluated by reserving different margins for the working and protection lightpaths. For 1 + 1 path protection, we find that the proposed mechanism can achieve a zero design margin (D-margin) for a working lightpath, thereby significantly improving network spectrum efficiency, while not sacrificing the availability of lightpath services. For SBPP, we find that an optimal D-margin should be identified to balance the spectrum efficiency and service availability; the proposed mechanism can save up to 0.5-dB D-margin for a working lightpath, while guaranteeing service availability.

Investigation of modulation format conversion for optical channel deaggregation in elastic optical network

Our research investigates an optical channel deaggregation technique based on modulation format conversion that may be used in elastic optical networks (EONs) to achieve high spectral efficiency, flexibility, and high data rate. The modulation format conversion technique from 8-ary phase shift keying (8-PSK) to two simultaneous quadrature phase shift keying (QPSK) at 50 Gb / s has been simulated and investigated. 8-PSK and the converted QPSK signals are investigated and compared in terms of bit error rate (BER) and quality factor (Q-factor), and it is demonstrated that they substantially reduce the complexity of transmission and reception process, at high data rates in EON. Additionally, this approach is further exploited to tailor a protection scheme for network survivability. Channel deaggregation, which divides the channel into working and protection paths, is used to implement a dedicated path protection scheme in EON. To evaluate the effect of various network conditions such as traffic load, modulation format, and BER on EON survivability, network simulations are performed on the ARPANET network.

Efficient dynamic routing in Spectrally-Spatially Flexible Optical Networks based on traffic categorization and supervised learning methods

In this paper, we focus on the efficient dynamic routing in Spectrally-Spatially Flexible Optical Networks (ss-fon) realized using Single-Mode Fiber Bundles (smfbs). We study two scenarios – unprotected network (np) and network protected by dedicated path protection (dpp) against a single link failure. For these configurations, we propose a dedicated optimization approach (Enhanced Adaptive Spectral-Spatial Allocation – e-assa), which makes use of the traffic categorization and application of different allocation strategies for different traffic categories. To select beneficial categorization rules, we employ supervised learning paradigm. We show that the selection of a beneficial regression algorithm to support network optimization cannot be performed based only on standard metrics like r2 but some additional measures/experiments are necessary. Then, we carry out extensive numerical experiments in order to tune the approach and to evaluate its efficiency based on the comparison with reference methods. The results prove high efficiency of the proposed optimization framework, which provides low blocking probability and significantly shorter processing time compared to the best of reference methods.

Proactive connection recovery strategy with recovery time constraint for survivable elastic optical networks

This paper presents a halfway signaling exchange shared path protection (HSE-SPP) on the backup route for a fast connection recovery strategy. In the proposed HSE-SPP, a pre-assigned intermediate node on the backup route is chosen for signaling exchange. When connection fails, source and destination nodes simultaneously generate backup connection setup messages to the pre-assigned intermediate node on the reserved backup route. At the intermediate node, signaling process occurs, and acknowledgment is generated for data transmission to the respective end nodes. Consequently, connection recovery time by applying HSE-SPP becomes very low. Simulations are performed for network parameters and results are verified with existing strategies. The average recovery time (RT), bandwidth blocking probability (BBP), bandwidth provisioning ratio (BPR), and resource overbuild (RO) ratio of HSE-SPP for ARPANET is 13.54ms, 0.18, 3.02, 0.55, and for dedicated path protection (DPP) are 13.20ms, 0.56, 6.30, 3.75 and for shared path protection (SPP) 22.19ms, 0.22, 3.23, 0.70 respectively. Similarly, average RT, BBP, BPR and RO of HSE-SPP for COST239 are 8.33ms, 0.04, 1.64,0.26, and for DPP 4.23, 0.47, 3.50, 2.04, and for SPP 11.81, 0.08, 1.66, 0.27 respectively. Hence, results of the proposed strategy are better in terms of RT, BBP, BPR, and RO ratio.

Towards an Efficient and Exact Algorithm for Dynamic Dedicated Path Protection.

We present a novel algorithm for dynamic routing with dedicated path protection which, as the presented simulation results suggest, can be efficient and exact. We present the algorithm in the setting of optical networks, but it should be applicable to other networks, where services have to be protected, and where the network resources are finite and discrete, e.g., wireless radio or networks capable of advance resource reservation. To the best of our knowledge, we are the first to propose an algorithm for this long-standing fundamental problem, which can be efficient and exact, as suggested by simulation results. The algorithm can be efficient because it can solve large problems, and it can be exact because its results are optimal, as demonstrated and corroborated by simulations. We offer a worst-case analysis to argue that the search space is polynomially upper bounded. Network operations, management, and control require efficient and exact algorithms, especially now, when greater emphasis is placed on network performance, reliability, softwarization, agility, and return on investment. The proposed algorithm uses our generic Dijkstra algorithm on a search graph generated “on-the-fly” based on the input graph. We corroborated the optimality of the results of the proposed algorithm with brute-force enumeration for networks up to 15 nodes large. We present the extensive simulation results of dedicated-path protection with signal modulation constraints for elastic optical networks of 25, 50, and 100 nodes, and with 160, 320, and 640 spectrum units. We also compare the bandwidth blocking probability with the commonly-used edge-exclusion algorithm. We had 48,600 simulation runs with about 41 million searches.

A Hybrid Dedicated Path Protection Strategy in EONs

A Hybrid Dedicated Path Protection Strategy in EONs

A parallel cross-connection recovery scheme for dual link failure in elastic optical networks

Abstract In this paper, we proposed a fast recovery strategy for a dual link failure (DLF) in elastic optical network (EON). The EON is a promising solution to meet the next generation higher bandwidth demand. The survivability of high speed network is very crucial. As the network size increases the probability of the DLF and node failure also increases. Here, we proposed a parallel cross connection backup recovery strategy for DLF in the network. The average bandwidth blocking probability (BBP), bandwidth provisioning ratio (BPR), and recovery time (RT) for our proposed Intermediate node cross-connect backup for shared path protection (INCB-SPP) for ARPANET are 0.38, 2.71, 4.68 ms, and for DPP 0.70, 6.02, 8.71 ms and for SPP 0.40, 2.87, and 16.33 ms respectively. The average BBP, BPR, and RT of INCB-SPP for COST239 are 0.01, 1.71, 3.79 ms and for DPP are 0.39, 3.50, 8.20 ms and SPP are 0.04, 1.75, and 12.47 ms respectively. Hence, the proposed strategy shows lower BBP, fast connection recovery, and BPR when compared with the existing shared path protection (SPP) and dedicated path protection (DPP) approaches. Simulation is performed on ARPANET and COST239 topology networks.

Multiple leaf-ringing based protection algorithm with spectrum defragmentation for multicast traffic in elastic optical network

Elastic optical networks (EONs) have realized high-speed data transmission with attractively efficiency and flexibility in resource utilization. In order to guarantee the reliability and increase the efficiency of the multicast transmission in EONs, we propose a multiple leaf-ringing based protection algorithm with spectrum defragmentation (MLRP-SD) in this article. The proposed algorithm firstly sorts the destination nodes of a multicast service into multiple groups. Then, it constructs one leaf ring for all the destination nodes in one group and two dedicated trunk paths (including one protection trunk path) from the source to each constructed ring. Since a leaf ring can provide protection for the destination nodes in its corresponding group, the reliability of multicast traffic can be improved. And the use of leaf rings can reduce the spectrum consumed in service protection compared to the traditional dedicated path protection (DPP) algorithms. In order to further improve the efficiency, the proposed MLRP-SD algorithm triggers spectrum defragmentation to re-optimize resource utilization in the network when sufficient available spectrum resources cannot be found along the sought protection trunk paths. The simulation results show that the proposed MLRP-SD algorithm can guarantee the reliability of multicast traffic with low service blocking probability.

WITHDRAWN: Resource efficient recovery scheme for double link failures in elastic optical networks

Abstract In order to avoid, double link failure in the optical network, we proposed a rapid connection recovery scheme for the survivable double link in elastic optical network (EON). The elastic optical network provides very high and flexible bandwidth as per the user’s requirement. Larger network have more number of failure probability. To control such failure, our proposed strategy provides a alternate backup light path by using minimum resources. Our proposed recovery scheme (PRS) provide better results in terms of recovery time, bandwidth blocking probability (BBP), and bandwidth provisioning ratio, when compared with the existing shared path protection (SPP) and dedicated path protection (DPP) schemes. ARPANET and COST239 topologies are considered for simulation.

QoS-aware protection in elastic optical networks with distance-adaptive and reconfigurable modulation formats

• Proposal on QoS-aware protection combined with reconfigurable modulation formats. • A novel network design formulation for QoS-aware protection. • Protection based on traffic differentiation brings significant spectral saving. Elastic optical networks have recently emerged as one of the most promising technologies for creating next-generation optical core networks thanks to the adaptive spectrum allocation mechanism. In order to achieve higher spectrum efficiency and exploit elastic optical networking technology, in this paper, we introduce a novel perspective on re-designing dedicated path protection for elastic optical networks. First, inspired by the observation that, in distance-diverse network topologies, the transmission margin between the working and protection route could be wide enough and therefore, the most feasibly spectrum-efficient modulation format could be assigned according to the specific condition of each route rather than applying a single modulation format that is able to cope with the worse condition of the route as currently adopted in traditional designs. Such more granular in transmission adaption is powered by the fast reconfiguration of state-of-the-art elastic transponders and this paves new opportunities in leveraging the spectrum efficiency. Second, the characteristics of traffic traveling in fiber links could be furthermore exploited to tailor the protection services to the actual requirement instead of enforcing the same level of protection for the entire traffic. Specifically, premium traffic today accounts for only 25 % and the remained traffic is best-effort and in taking advantage of this insight, dedicated path protection could be re-designed to ensure just-enough bandwidth provision for premium traffic in case of failures while possibly accepting best-effort traffic discard. In exploiting both the reconfiguration capability and traffic differentiation, a new quality-of-service aware protection framework for the design of elastic optical networks with the capability of distance-adaptive and reconfigurable modulation format assignment is provided. We introduce the node architecture supporting our proposal and provide an optimal design formulation in the form of integer linear programming model to maximize the spectral utilization efficiency. We have also applied extensively experimental simulations to evaluate the performance of our proposed solution in comparison with that of appropriate conventional approaches on a realistic network topology, i.e. COST239. The obtained numerical results prove that our developed solution significantly outperforms the conventional ones, in terms of spectrum efficiency, and it has been revealed that permitting reconfiguration of transmission parameters in switching from working routes to protection ones could result up to 20 % spectral saving in most favorable conditions. Furthermore, incorporating the protection service differentiation could substantially boost spectrum efficiency. For the present ratio of premium traffic– roughly 25 % , our proposal reveals that a spectral saving of up to more than 80 % could be attained and on the whole, the developed solution tends to be more profitable with the medium and high-load traffic conditions.

Survivable time-aware traffic grooming in spatial division multiplexing elastic optical networks with minimized crosstalk

The space division multiplexing (SDM) technology with multi-core fiber (MCF) is a solution to increase the capacity of optical links. MCF undergoes involuntary challenges due to the interference of transmitted signals on congested multiple cores, named inter-core crosstalk (XT). On the other hand, to protect the huge traffic of users, applying survivability and traffic grooming at the same time is necessary. We study dynamic survivable time-aware grooming, routing, spectrum and core allocation considering XT in SDM-enabled elastic optical networks (SDM-EONs) with MCF and propose survivable grooming time-aware XT-unaware/aware (TXTUSG/TXTASG) algorithms. Using these algorithms, full survivability and optimum utilization of network resources are provisioned by the dedicated path protection and grooming strategies. In addition, the quality of receiving signals is assured by overcoming XT. Furthermore, an attempt is made to reduce fragmentation by involving time dimension. Our simulation results affirm that blocking rate always decreases in suggested algorithms owing to fragmentation reduction, spectrum utilization increase, and bandwidth variable transponders performance enhancement.

A Resource Efficient Recovery Strategy for a Failure in Elastic Optical Networks

In the last few years, internet traffic increases continuously due to the more use of live streaming and social sites. To accommodate such high traffic demand the more bandwidth is required. The elastic optical network (EON) is a promising solution for the capacity expansion that can meet the future bandwidth requirement. The EON can provide a higher bit rate. In this paper we purposed a recovery strategy for failure in EON. Our purposed strategy shows the more acceptance rate for randomly generated source (s)-destination (d) requests. Here we considered two topologies viz. COST239 and NSFNET. Then evaluate their performance for Recovery Time, bandwidth blocking probability (BBP) and network capacity utilization (NCU), in which our purposed scheme provides lesser BBP and lower NCU for both topologies and low recovery time than shared path protection (SPP and dedicated path protection (DPP).

On the spectrum-efficiency of QoS-aware protection in elastic optical networks

Elastic optical networks technologies feature several benefits including higher spectral efficiency, system capacity and therefore have been widely viewed as the promising paradigm for next-generation optical transport networks. Dedicated path protection for elastic optical networks has been of ever-increasing importance in the era of information society thanks to its near-immediate recovery speed and remarkably simple operations in guaranteeing the connectivity of information flows. Inspired by the observation that the today premium network traffic traveling in fiber links accounts for roughly 25% of total traffic and the best-effort traffic constitutes the remaining, we propose a new design for elastic optical networks with dedicated path protection tailoring to the actual traffic profile rather than enforcing the same protection service for both traffic types as with conventional approaches. Our proposal exploits the flexible baud-rate transponders shared between the working and protection mode, featuring lower baud-rate operation for protection mode to provide just enough bandwidth for premium traffic. To maximize the impact of protection service differentiation, we present a novel integer linear programming taking into account the proposed quality-of-service-aware protection aiming at minimizing the spectrum usage. Numerical results on a realistic topology, COST239, are provided to assess the efficiency of our proposal compared to the traditional approach and it has been highlighted that having quality-of-service-aware protection being adapted to the actual traffic characteristic presents significant spectrum savings. With the current estimate of premium traffic of 25%, our study suggests that more than 30% spectral saving could be achieved and generally the low-load condition is more profitable than the medium and high-load ones.

A Priority-Based Multiobjective Design for Routing, Spectrum, and Network Coding Assignment Problem in Network-Coding-Enabled Elastic Optical Networks

In elastic optical networks, the use of network coding (NC) represents a new dimension to further optimize spectrum efficiency, and indeed, combining NC and dedicated path protection has paved the way for achieving greater capacity efficiency, while retaining the merit of near-instantaneous recovery. In order to harness the NC benefits, a more complicated problem called routing, spectrum, and network coding assignment (RSNCA) has to be solved, and in this article, we propose a priority-based multiobjective design for the RSNCA problem aiming at maximizing the network throughput in the constrained bandwidth capacity and simultaneously minimizing the spectrum link usage for accepted demands. The multiobjective design is based on the weighting method, and we present a rigorous analysis on the impact of weight coefficients to the priority of constituent objectives. The efficacy of our design proposal is benchmarked with reference ones based on the traditional single-objective model and for both coding and noncoding approaches on various realistic topologies. It is highlighted that the application of NC brings about considerable throughput enhancement, and furthermore, the multiobjective RSNCA design is highly more efficient than the single-objective RSNCA, as up to more than 50% saving on spectrum link usage could be attained.

Spectrum Expansion/Contraction and Survivable Routing and Spectrum Assignment problems on EONs with time-varying traffic

For serving time-varying traffic on an Elastic Optical Networks (EONs), the spectrum allocated previously for the connection request should be expanded or contracted to meet the traffic requirement. For the survivable connection, both the primary and the backup lightpaths of the connection request should be expanded/contracted at the same time. In this paper, the Survivable Routing and Spectrum Allocation (SRSA) problem and the Spectrum Expansion Contraction (SEC) problem for SRSA on EONs with time-varying traffic are studied. In this article, two protecting schemes, Dedicated Path Protection (DPP) and Shared Backup Path Protection (SBPP) are considered. For each protecting scheme, two dynamic survivable routing algorithms and the respective SEC operations are developed to solve it. In the proposed algorithms, both the weighted hop distance and spectrum fragmentation are considered jointly. These algorithms are examined through simulations to find the best parameter for each algorithm. The results show that the blocked ratio (BR) of requests can be reduced by about 3%, if the spectrum fragmentation is considered. And, using SEC operation in time-varying traffic can reduce the BR of request about 1% and speed up the computation compared to the normal release and add operation.