Traffic-aware elastic optical networks to leverage energy savings

Machine learning (ML) is an effective solution to deal with some networking issues in large scale optical transport networks. Alarm (caused by failure, disaster, etc.) prediction is a typical and important use-case, where ML algorithm can work to predict events in advance. By accurate prediction, network administrators can be guided to undertake preventive measures ahead of time, thus avoiding the adverse effect. For training and testing of such event prediction models, it’s first and foremost to build a high-quality data set from real networks. However, the data collected from large-scale optical transport networks are inferior in quality and demand prompt pre-processing, for they are sometimes invalid, incomplete, inconsistent, and even inaccurate. After data pre-processing, there is only a small amount of available data left to build an ML data set, which extremely limits the performance of the alarm prediction model. This paper proposes a machine-learning-based alarm prediction method using self-optimizing data augmentation based on generative adversarial networks (GANs) for optical transport networks. Experimental results on a commercial backbone synchronous digital hierarchy (SDH) network with 274 nodes and 487 links demonstrate that the proposed method can achieve high accuracy for alarm prediction.

This book presents an in-depth deliberation on optical networks in four parts, capturing the past, present, and ensuing developments in the field. Part I has two chapters presenting an overview of optical networks and the enabling technologies. Part II has three chapters dealing with the single-wavelength optical networks: optical LANs/MANs, optical access networks using passive optical network architecture, SONET/SDH, optical transport network and resilient packet ring. Part III consists of four chapters on WDM-based optical networks, including WDM-based local/metropolitan networks (LANs/MANs) using single and multihop architectures over passive-star couplers, WDM/TWDM access networks as an extension of PONs with WDM transmission, WDM metro ring networks covering circuit-switched (using point-to-point WDM and wavelength-routed transmission) plus packet-switched architectures and WDM long-haul backbone networks presenting the offline and online design methodologies using wavelength-routed transmission. Part IV deals with some selected topics in six chapters. The first deals with transmission impairments and power-consumption issues in optical networks, while the next three chapters deal with the survivable optical networks, network control and management techniques, including GMPLS, ASON, and SDN/SDON, and datacenter networks using electrical, optical, and hybrid switching techniques. The final two chapters present elastic optical networks using flexible grid for better utilization of the optical-fiber spectrum and optical packet and burst-switched networks. The three appendices present the basics of the linear programming techniques, noise processes encountered in the optical communication systems, and the fundamentals of queuing theory and its applications in telecommunication networks. (238 words)

This paper studies the overall energy consumption of a pan-European optical transport network for three different time periods: today and in five and ten years from now. In each time period the pan-European network was dimensioned using traffic predictions based on realistic data generated by the optical networking roadmap developed in the framework of the European project Building the Future Optical Network in Europe—BONE. A wavelength routed wavelength division multiplexed optical network based on either transparent or opaque node architectures was examined considering exclusively either 10 Gbit/s or 40 Gbit/s per channel data rates. The results manifest that transparent optical networking technologies are expected to provide significant energy savings of the order of 35% to 55%. It was also shown that the migration towards higher data rates, i.e., from 10 Gbit/s to 40 Gbit/s, is assisting in improving the overall energy efficiency of the network.

Optical networks—the electro-optic reality

With optical technology evolution, it becomes possible to perform all optical traffic grooming (AOTG) with a very fine granularity. In the context of flexible optical networking, AOTG paves the way to new possibilities in future transport networks. Finding the best trade-off between electrical and optical aggregation in intrinsically multi-layer transport networks is a complex challenge for operators. This paper compares CAPEX results and resource fill-in performances of electrical and optical aggregation solutions, through a real multilayer transport network case study.

Bandwidth utilization and management advancements of Multi-Granular Optical Transport Networks (MG-OTN) have been shown to couple with power savings through lowered port counts. In this paper, we propose energy-efficient design of MG-OTNs by adopting multiple power levels at the MG nodes. Our proposed scheme combines the advantages of a previously proposed energy-efficient design method and introducing dual power state behavior to the MG nodes. According to the proposed scheme, a node can be either in the on state where it can add, drop and forward traffic at any granularity, or in the sleep state where it can only add and drop traffic, and accordingly, it saves the switching power consumption due to pass-through traffic. Through extensive simulations, we evaluate the proposed dual power state-based MG-OTN design in terms of energy-efficiency. Numerical results confirm that for all tested traffic patterns, putting a certain number of nodes in the sleep mode can guarantee significant power savings. Furthermore, we provide information on optimal selection of the nodes that have to be put in the sleep mode. Moreover, we study the topology dependence of the proposed scheme and show that high network connectivity leads to high power savings.

Optical WDM networks can be employed as the transport medium technology for cloud computing services since they have high capacity and low delay, and they satisfy the service requirements by the help of the control plane. Recent research has shown that cloud services can be efficiently provisioned based on anycast or manycast paradigms. In this paper, we focus on the energy savings in the optical transport network which forms a communication infrastructure for the cloud services based on the manycast paradigm. We propose an optimization model to maximize the energy savings by putting the wavelength routing modules of the optical nodes in the power saving mode. Based on the optimization model, we propose an evolutionary algorithm, namely the Evolutionary Algorithm for Green Light-tree Establishment (EAGLE) which can provide lower runtime for large topologies and find a suboptimal solution. We evaluate the performance of our optimization model by running EAGLE under a topology lying on four different time zones, i.e., NSFNET. Simulation results verify that selecting a feasible number of nodes to put their wavelength routing modules in the power saving mode leads to significant energy savings in transportation of the cloud services over WDM networks. Furthermore, the proposed scheme does not introduce a resource consumption penalty when compared to the wavelength minimizing approach.

The volume of traffic carried on the Optical Transport Network (OTN) is continuously growing, not only due to the increase of new services, new applications, and the number of both connected users and smart devices, but also owing to the rapidly growing Data Center Interconnect (DCI) market. As a result, telecom operators need to upgrade their transport networks to cope with these new traffic requirements. This tremendous increase in bandwidth demand will also introduce energy bottlenecks in OTNs. The telecommunication networks' significant Greenhouse Gas Emissions (GGE) is another challenge that must be addressed in OTN design and planning policies. Thus, energy-efficient OTN architectures are currently attracting the attention of telecom operators. The candidate OTN architectures are: (1) the conventional Dense Wavelength Division Multiplexing (DWDM) fixed grid with high Single Line Rates (SLRs); (2) the conventional DWDM fixed grid adopting Mixed Line Rates (MLRs); and (3) the Elastic Optical Network (EON) or flexigrid-based architecture which is enabled by the Optical Orthogonal Frequency Division Multiplexing (O-OFDM) technique. This paper evaluates the power consumption of the abovementioned OTN architectures under different traffic loads and patterns, as well as different network physical topologies. In order to perform the evaluation, new heuristic algorithms are specifically developed for the green design and planning of data center optical interconnects.

Content caching is an effective technique that reduces network power consumption by reducing the path between users and requested video content. This paper examines the benefit of caching in an IP over WDM core network with respect to current and future networks. It compares the power savings due to caching in current implementations of optical networks to potential power savings when future optical network features are realized. Future optical core networks are considered with three major power efficiency improvements over current networks. First, network devices are equipped with sleep-mode capabilities where inactive parts of storage devices are put in low-power mode. Second, optical bypass is employed where intermediate IP routers are not engaged in traffic routing. Third, the power consumption of router ports is significantly reduced, consequently reducing the power consumption of transport. The results show that content caching is effective in reducing power consumption under both current and future optical networks, making caching a successful option for video delivery in the future Internet.

The right distribution concept and the right service concept play an important role in strategic decisions about a specific production concept and the location of production sites, especially for physical goods. This paper shows which design possibilities are suitable for distribution networks and service networks for particular markets and product characteristics, depending on the design of the production network. Secondly, the design possibilities for retail networks for decentralized distribution are deduced. Thirdly, the design possibilities for appropriate transport networks are considered. The result is a new sort of framework with which the appropriate concepts can be determined using a combination of generic characteristic values and the portfolio approach. The determination is integrative: a combination of designs of the production, distribution, service and transport networks both suit the product and the targeted customer segment, and fit well together.

Optimal transport network design for both traffic safety and risk equity considerations

Elastic optical network (EON) is a promising candidate for the next generation optical transport network because of its high spectrum efficiency and flexible spectrum allocation. However, to migrate from today’s dense wavelength division multiplexing (DWDM) network to EON, optical nodes such as reconfigurable optical add/drop multiplexers (ROADMs) should be replaced with the ones with expensive flexi-grid wavelength selective switches (WSSs). Thus, whether and how today’s optical network will be evolved to EON is still under debate. Meanwhile, with the technical maturity of optical super-channels that transmit bit rates at the level of 1 Tb/s, super-channels are expected to dominate the future optical transport network because of their attractiveness of high spectrum efficiency and superior cost effectiveness. In this paper, we propose a new quasi-coarse wavelength division multiplexing (Quasi-CWDM) optical network architecture that is compatible to today’s WDM network in spectrum operation, while still maintaining the flexibility of adaptation between the bit rate and the transparent reach of an optical super-channel, but not requiring expensive flexi-grid WSSs. Specifically, the Quasi-CWDM optical network employs large fixed frequency grids, whose spacing falls between the traditional CWDM and DWDM, e.g., 200 GHz or 400 GHz. To maintain the flexibility between the bit rate and the transparent reach of an optical super-channel, different modulation formats are chosen according to channel physical distances. To minimize network hardware cost and maximize carried user traffic demand, we develop a mixed integer linear programming (MILP) model and a heuristic algorithm that can efficiently groom upper-layer IP traffic onto the optical layer by optical super-channels. We compare the design based on the Quasi-CWDM network to those based on the DWDM network and the advanced EON. It is found that the proposed Quasi-CWDM network has a much lower hardware cost than the other two types of networks, while achieving spectrum efficiency close to EON.

Based on the virtualization technique in optical networks, virtual transport network services (VTNS) has been introduced as a new kind of service in transport networks. With VTNS, transport providers are able to provide their customers entire virtual topologies instead of traditional end-to-end connections. This letter analyzes the new characteristics (i.e., multiple operators, diversified services) aiming at the survivability problem in virtualized optical transport networks, and proposes three novel protection schemes for VTNS against the new features. For the first time, VTNS with the proposed protection schemes are demonstrated on the flexi-grid optical networks testbed with commercial optical transport equipments. Additionally, the performances of the proposed protection schemes have been evaluated via simulations.

Due to widespread applications and rapid development of cloud computing and Internet services, hyperscale data centers have experienced an unprecedented demand for networking. Data center networks are required not only to handle fast-growing traffic, which doubles almost every one to two years, but also to provide high flexibility and availability to support rapidly changing businesses as well. Therefore, hyperscale data center networks have become one of the main drivers for optical interconnect technologies in recent years. In this article, technologies for scaling optical interconnects for inter-data center interconnects (DCIs) are presented. We first describe hyperscale data center network architectures and requirements, as well as the differences between carrier’s optical transport networks and DCI optical networks, with the main focus on metro-DCI and campus-DCI networks. The scale and fast growth rates of DCI networks require innovations not only in data plane technologies but also in control and management planes as well. In data planes, high-capacity flexible coherent technology, pluggable wavelength-division-multiplexing (WDM) optical transponders, including 100G direct-detection four-level pulse-amplitude modulation (PAM4) and coherent 400ZR/800ZR, and flex-grid and disaggregated reconfigurable optical add-drop multiplexer (ROADM) optical networks are described. Control and management planes are an integral part of optical transport networks and crucial for effectively operating DCI networks. We show that standard protocols, data models, and modular design of a software platform are essential to building a scalable open and disaggregated optical network, which is fundamental to enabling high automation and intelligence in an optical network. An example control and management platform is discussed in detail. With current fiber capacity approaching the nonlinear Shannon limit, challenges to further scale DCI networks and some potential technologies to support ever-increasing traffic growth are discussed at the end.

Accommodating of future demand uncertainty is an important issue in IP networks to continue at acceptable level of service during high traffic load periods. This aspect should also be considered during optical backbones design for high-speed client networks. This paper presents an intelligent fuzzy adaptive approach for spare bandwidth management in Dense Wavelength Division Multiplexing (DWDM) optical transport network based on link state variables. First forecasted part of demand matrix is routed in the network using shortest path algorithm. Then, the available wavelengths are allocated to future demand uncertainties. The fuzzy controller decides according to bandwidth availability and demand uncertainty memberships. The simulation results achieved from the Pan European test bench network demonstrate the efficiency of proposed approach to accommodate future demand uncertainty in uncertain environments.