Xiaosong Yu

Energy-efficient traffic grooming in sliceable-transponder-equipped IP-over-elastic optical networks [invited]

The sliceable optical transponder, which can transmit/receive multiple optical flows, was recently proposed to improve a transponders flexibility. The upper-layer traffic can be offloaded onto an optical layer with “just-enough transponder” resources. Traffic grooming evolves as the optical transponder shifts from fixed to sliceable. “Optical-layer grooming” enabled by a sliceable optical transponder can reduce the number of power-consumption components (e.g., IP ports and optical transponders). In this paper, energy-efficient traffic grooming in IP-over-elastic optical networks with a sliceable optical transponder is studied. Three bandwidth-variable transponders (BVTs) based on their sliceability, namely, non-sliceable BVTs, fully sliceable BVTs, and partially sliceable BVTs, are investigated. For each transponder, we develop energy-minimized traffic grooming integer linear programming (ILP) models and corresponding heuristic algorithms. Comprehensive comparisons are performed among the three types of transponders, and two interesting observations emerge. First, we find that significant power savings can be achieved by using a sliceable optical transponder. Second, we find that power savings do not keep improving linearly while transponder sliceability is increasing, and traditional electrical-layer grooming is still required to work together with optical-layer grooming to reduce power consumption.

Dynamic Traffic Grooming in Sliceable Bandwidth-Variable Transponder-Enabled Elastic Optical Networks

Traffic grooming has evolved to present some new features in sliceable bandwidth-variable transponder enabled elastic optical networks (SBVT-EON). One of the new features is “optical traffic grooming,” in which multiple optical flows from/to different sources/destinations can be groomed onto a sliceable transponder. When establishing a new connection request in SBVT-EON, a key problem is how to coordinate electrical and optical traffic grooming. In this study, we propose a three-layered auxiliary graph (AG) model to address mixed-electrical-optical grooming under dynamic traffic scenario. By adjusting the edge weights of AG, we can achieve various traffic-grooming policies for different purposes. Also, we propose two spectrum reservation schemes that can efficiently utilize the capacity of a transponder. We compare different traffic-grooming policies under two spectrum reservation schemes, and a tradeoff is shown to exist among the policies. We also evaluate their performances for different network topologies with different resource provisions.

Experimental demonstration of OpenFlow-based control plane for elastic lightpath provisioning in Flexi-Grid optical networks

Due to the prominent performance on networking virtualization and programmability, OpenFlow is widely regarded as a promising control plane technology in packet-switched IP networks as well as wavelength-switched optical networks. For the purpose of applying software programmable feature to future optical networks, we propose an OpenFlow-based control plane in Flexi-Grid optical networks. Experimental results demonstrate its feasibility of dynamic lightpath establishment and adjustment via extended OpenFlow protocol. Wireshark captures of the signaling procedure are printed out. Additionally, the overall latency including signaling and hardware for lightpath setup and adjustment is also reported.

Prospects and research issues in multi-dimensional all optical networks

Research into all optical network (AON) technology has been ongoing over the past decade, and new features are constantly being developed. The advantages of AON include large-bandwidth provisioning, lowlatency transmission and low energy consumption. The basic concept underlying AON is transmission of data signals entirely through the optical domain from source to destination nodes, with no optical-electrical-optical (O-E-O) conversion at intermediate nodes. The technologies used to implement AON have undergone a series of evolutions, which encompass time division multiplexing (TDM), frequency division multiplexing (FDM), and space division multiplexing (SDM). Multi-dimensional AON (MD-AON), which leads the trend of AON’s future architecture, provides a vibrant state for emerging applications such as cloud computing and Internet of Things (IoT). In this article, we review the evolution of AON architectures based on the different all optical switching and multiplexing technologies (i.e., TDM, FDM, and SDM), which is one of the main areas of focus in this article. The other main area is detailed discussion of implementations such as data plane and control plane technologies as well as resource optimization technologies for realizing AON. We also introduce several AON testbeds with their compositions and functions, and some potential application scenarios that can be implemented based on these testbeds摘要创新点全光网技术是光通信领域的技术前沿与研究热点, 受到了学术界和工业界的广泛关注, 其优势在于能够提供大带宽、 低时延、 安全、 节能的服务保证。 全光网的基本定义是信号从源节点到目的节点的传输和交换过程全部在光域进行, 中间节点不进行 “光-电-光” 处理。 针对这一特征, 本文从 “时、 频、 空” 三个维度回顾了全光网技术的发展, 分析了每种技术的特点与优势, 提出了多维全光交换网络的体系结构, 并从数据平面、 控制平面和应用平分别描述了多维全光网的关键使能技术。 同时也对当前国内外先进的全光网络创新平台进行了介绍与分析, 展望了针对数据中心互联, 网络虚拟化, 资源按需提供等方面的全光网创新应用。

Migration from fixed grid to flexible grid in optical networks

Optical WDM backbone networks based on fixed spectrum grid have limitations such as low spectrum utilization and rigidity in provisioning for heterogeneous rates. Flexible-grid technologies can alleviate these limitations for on-demand provisioning. These technologies represent promising candidates for future optical networks supporting beyond-100-Gb/s signals. However, a one-time green-field deployment of flexible-grid technologies may not be practical, as the already-made investment in existing fixed-grid WDM networks needs to be preserved, and interruptions to ongoing services need to be minimized. Therefore, we envision that fixed-and flexible-grid technologies will coexist, which will bring the challenge of interoperating fixed-and flexible-grid equipment. It is also important to design the optimum migration strategy to maximize cost effectiveness and minimize service interruption. In this article, we discuss the key aspects of network architectures supporting coexistence of fixed and flexible grid technologies, and outline the challenges of network operations. We also propose and evaluate different migration strategies from fixed grid to flexible grid under different network scenarios.

Global Resources Integrated Resilience for Software Defined Data Center Interconnection Based on IP Over Elastic Optical Network

We propose a novel global resources integrated resilience (GRIR) algorithm for a software defined data center interconnection architecture based on IP over elastic optical network (EON). The proposed algorithm provides resilience using the multiple stratums resources and enhances the data center service resilience responsiveness to the dynamic end-to-end recovery demands in case of the converged optical node failure. Our simulation results indicate that GRIR achieves significant improvements in terms of path blocking probability, resilience latency and resource occupation rate, compared with other resilience algorithms.

Static routing and spectrum assignment in co-existing fixed/flex grid optical networks

We consider the static routing and spectrum assignment (RSA) in co-existing fixed/flex grid optical networks. Integer Linear Programming (ILP) formulations are presented to minimize the utilized spectrum, and several heuristic algorithms are proposed and simulated.

Novel control plane framework and protocol extensions for Spectrum-Efficient Optical Transport Networks

Abstract Spectrum-Efficient Optical Transport Networks (SE-OTN), the most important character of which is high spectrum efficiency due to flexible grid, have attracted much attention recently. However, it cannot be employed for practical use since most of the related protocols are immature. This paper mainly focuses on the framework and protocol extensions for the control plane of SE-OTN. A novel control plane framework is designed combining the advantages of Generalized Multi-Protocol Label Switching (GMPLS) and Path Computation Element (PCE), and several routing and spectrum assignment (RSA) models are built. Furthermore, motivation and extension solutions for Open Shortest Path First-Traffic Engineering (OSPF-TE), Resource ReSerVation Protocol-Traffic Engineering (RSVP-TE), and PCE Protocol (PCEP) are proposed based on this framework. An experimental testbed of large-scale spectrum-efficient optical networks with the capability of supporting 1000 GMPLS-based control nodes has been built to validate the performance of the protocols and algorithms, and some numeric results and analysis are given finally. Numeric results show that our proposed Centralized Routing and Centralized Spectrum Assignment (CR+CSA) model has better performance than Centralized Routing and Distributed Spectrum Assignment (CR+DSA) and Distributed Routing and Distributed Spectrum Assignment (DR+DSA), and spectrum defragmentation algorithm based on spectrum compactness can get good performance in the CR+CSA model.

When and how should the optical network be upgraded to flex grid

This paper addresses the problem of gradual migration from fixed grid to flex grid. We discuss how to perform spectrum assignment in a mixed fixed/flex network, and we propose and compare three upgrade strategies under two traffic models in four different scenarios.

Auxiliary graph model for dynamic traffic grooming in elastic optical networks with sliceable optical transponder

An auxiliary graph model with corresponding spectrum reservation schemes was proposed for dynamic traffic grooming in sliceable transponder equipped elastic optical networks. Various traffic grooming policies can be achieved by adjusting the edge weights in the auxiliary graph.