Chen Ma

Traveling repairman problem for optical network recovery to restore virtual networks after a disaster [invited]

Virtual networks mapped over a physical network can suffer disconnection and/or outage due to disasters. After a disaster occurs, the network operator should determine a repair schedule and then send repairmen to repair failures following the schedule. The schedule can change the overall effect of a disaster by changing the restoration order of failed components. In this study, we introduce the traveling repairman problem to help the network operator make the schedule after a disaster. We measure the overall effect of a disaster from the damage it caused, and we define the damage as the numbers of disconnected virtual networks, failed virtual links, and failed physical links. Our objective is to find an optimal schedule for a repairman to restore the optical network with minimum damage. We first state the problem; then a mixed integer linear program (MILP) and three heuristic algorithms, namely dynamic programming (DP), the greedy algorithm (GR), and simulated annealing (SA), are proposed. Finally, simulation results show that the repair schedules using MILP and DP results get the least damage but the highest complexity; GR gets the highest damage with the lowest complexity, while SA has a good balance between damage and complexity.

Bandwidth-adaptability protection with content connectivity against disaster in elastic optical datacenter networks

Due to disasters in communication networks, the risk of large-scale failure is on the rise. Hence, how to recover failed requests caused by disaster with minimum spectrum resources is an important issue for network operators. In the past years, elastic optical networks provide a new way to reduce the spectrum consumption in optical networks. Based on the technology, bandwidth-adaptability protection with content connectivity (BCP) is proposed in this study. We first introduce the concept of BCP, which includes path calculation and spectrum allocation. For path calculation, working path and backup path employ links in different shared risk link groups to avoid disaster failure in optical networks. For spectrum allocation, modulation format of backup path is adjusted according to the requirement of point-to-content requests to reduce the spectrum consumption. Then, an integer linear program and two heuristic algorithms (BCP_KSP, BCP_MSP) are proposed for static and dynamic traffic scenarios, respectively. Simulation results show that, compared to traditional method without bandwidth adaptability, BCP has better performance in terms of spectrum resource utilization and blocking probability.

Energy efficiency and blocking reduction for tidal traffic via stateful grooming in IP-over-optical networks

The growing popularity of high-speed mobile communications, cloud computing, and the Internet of Things (IoT) has reinforced the tidal traffic phenomenon, which induces spatio-temporal disequilibrium in the network traffic load. The main reason for tidal traffic is the large-scale population migration between business areas during the day and residential areas during the night. Traffic grooming provides an effective solution to aggregate multiple fine-grained IP traffic flows into the optical transport layer by flexibly provisioning lightpaths over the physical topology. In this paper, we introduce a comprehensive study on energy efficiency and network performance enhancement in the presence of tidal traffic. We propose and leverage the concept of stateful grooming to apply differentiated provisioning policies based on the state of network nodes. We formulate and solve the node-state-decision optimization problem, which can decide the specific state of network nodes when a certain traffic profile is given, considering the trade-off between energy efficiency and blocking performance with a multi-objective integer linear program (MOILP). Then, we propose an online traffic-aware intelligent differentiated allocation of lightpaths (TIDAL) algorithm, based on stateful grooming and the MOILP, to accommodate the dynamic tidal traffic. Our illustrative numerical results show that the proposed method can achieve a significant performance improvement in an energy-efficient way.

Scheme for optical network recovery schedule to restore virtual networks after a disaster

Virtual networks mapped over a physical network can suffer from network disconnection due to disasters. We propose an integer linear programming model to restore physical links with maximizing connectivity of virtual networks.

Survivable virtual optical network embedding with probabilistic network-element failures in elastic optical networks

To measure the survivability of virtual optical network embedding, a novel metric named virtual optical network failure probability (VON-FP) is presented in elastic optical networks. We then develop a failure-probability-aware virtual optical network embedding (FPA-VONE) algorithm considering different line rates to decrease VON-FP of each VON. Simulation results show that FPA-VONE provides lower average VON-FP than the baseline algorithm, as well as frequency slots (FS) usage.

Multiple traveling repairmen problem with virtual networks for post-disaster resilience

In network virtualization, when a disaster hits a physical network infrastructure, it is likely to break multiple virtual network connections. So, after a disaster occurs, the network operator has to schedule multiple teams of repairmen to fix the failed components, by considering that these elements may be geographically dispersed. An effective schedule is very important as different schedules may result in very different amounts of time needed to restore a failure. In this study, we introduce the multiple traveling repairmen problem (MTRP) for post-disaster resilience, i.e., to reduce the impact of a disaster. Re-provisioning of failed virtual links is also considered. We first formally state the problem, where our objective is to find an optimal schedule for multiple teams of repairmen to restore the failed components in physical network, maximizing the traffic in restored virtual network and with minimum damage cost. Then, we propose a greedy (GR) and a simulated annealing (SA) algorithm, and we measure the damage caused by a disaster in terms of disconnected virtual networks (DVN), failed virtual links (FVL), and failed physical links (FPL). Numerical result shows that both proposed algorithms can make good schedules for multiple repairmen teams, and SA leads to significantly lower damage in terms of DVN, FVL, and FPL than GR.

Node protection method with content-connectivity against disaster in disaster recovery center networks

With the growth of cloud computing and other high-bitrate disaster recovery center (DRC) support service, DRC networks play an important role in the future networks. But the nature or man-made disaster is the main threaten of survivability. In this paper, we focus on the protection of DRC node based on contentconnectivity against disaster in disaster recovery center networks. An integer linear programming (ILP) model is proposed for that. Simulation results shows that, the proposed method has better performance to deal with node failure with less backup spectrum resources.

Service-Aware Protection with Bandwidth Squeezing against Disaster in Elastic Optical Datacenter Networks

We propose a novel service-aware protection (SAP) with bandwidth squeezing against disaster in elastic optical datacenter networks. The simulation results show that proposed scheme has a better performance in blocking rate and spectrum resource utilization.

Differentiated quality-of-protection provisioning with probabilistic-shared risk link group in survivable flexi-grid optical networks

Abstract. A multilink failures model, i.e., probabilistic-shared risk link group (PSRLG), is adopted to investigate the problem of differentiated quality-of-protection (QoP) provisioning for flexi-grid optical networks. As a metric, service failure probability (SFP) is introduced to exactly examine the feasibility of differentiated QoP schemes, which denotes the failure probability of a connection during transmission. According to different reliability requirements, connection requests are divided into three classes, i.e., class high, class middle, and class low. Then two differentiated QoP provisioning schemes are proposed based on the class division, i.e., intraclass-shared resource scheme (ICSR scheme) and cross-class-shared resource scheme (CCSR scheme). The former allows a connection to share backup resources only with those connections in the same class, whereas the latter enables the connections in different classes to share backup resources. Simulation results show that our proposed schemes could well provide differentiated reliability with PSRLG constraint and achieve a good balance between reliability and resource efficiency. Moreover, the CCSR scheme achieves lower blocking probability, lower resource redundancy, and higher spectrum utilization without sacrificing reliability compared to the ICSR scheme.

p-Cycle Protection Approach with Maximum Spectrum Sharing in Elastic Optical Networks

In this paper, a p-Cycle protection approach with maximum spectrum sharing is proposed to reduce spectrum consumption. Simulation results show the proposed approach achieves lower blocking probability and resource redundancy than that without spectrum sharing.