Multicast backup reprovisioning problem for Hamiltonian cycle-based protection on WDM networks

As networks grow in size and complexity, the chance and the impact of failures increase dramatically. The pre-allocated backup resources cannot provide 100% protection guarantee when continuous failures occur in a network. In this paper, the multicast backup re-provisioning problem (MBRP) for Hamiltonian cycle (HC)-based protection on WDM networks for the link-failure case is studied. We focus on how to recover the protecting capabilities of Hamiltonian cycle against the subsequent link-failures on WDM networks for multicast transmissions, after recovering the multicast trees affected by the previous link-failure. Since this problem is a hard problem, an algorithm, which consists of several heuristics and a genetic algorithm (GA), is proposed to solve it. The simulation results of the proposed method are also given. Experimental results indicate that the proposed algorithm can solve this problem efficiently.     

Virtual infrastructure mapping in software-defined elastic optical networks

Software-defined networking (SDN) enables efficient and scalable network virtualization, which allows infrastructure resources such as computing and networking resources to be abstracted and outsourced as a service. The SDN technologies can be extended to the optical transport networks to achieve an intelligent and flexible resource management, thus achieving high-capacity, low-cost, and long-reach optical transport networks. In this paper, we introduce an architecture for software-defined elastic optical networks and study the virtual infrastructure (VI) mapping problem with the objective of minimizing the blocking probability. We propose a set of efficient heuristic algorithms, among which the Network followed by Compute Load Balancing (NCLB) algorithm is a novel attempt to solve the VI mapping problem by provisioning the networking resource first followed by allocating the computing resource. Furthermore, we propose a modified version of NCLB, called Network Depth-based NCLB (ND-NCLB), which confines the VI mapping assignment in a small-range sub-network to further optimize the physical network resource consumption. Through comprehensive simulations in various scenarios, we demonstrate that the proposed ND-NCLB algorithm achieves the best performance in terms of blocking probability compared to the other algorithms in this work.     

Upgrade-aware virtual infrastructure mapping in software-defined elastic optical networks

An emerging use case in software-defined networking is to provide efficient mapping of multiple virtual infrastructures (VIs) simultaneously over the same physical substrate (PS) which can increase the resource utilization of the PS, thus improving its provider’s revenue. In this paper, for the first time, we investigate a practical and yet theoretically challenging issue related to dynamic VI mapping in software-defined elastic optical networks while considering the presence of possible upgrade of the VIs and the optical layer constraints, which has not been addressed in any of the existing studies. More specifically, we investigate the following aspects: (1) Which revenue models are appropriate? (2) How to map a new VI request or to upgrade an existing VI to maximize the PS providers revenue? In particular, we study two different revenue models in terms of the incremental pricing policy and the binding pricing policy and propose a number of efficient heuristics to solve the upgrade-aware VI mapping (U-VIM) problem. We also perform comprehensive performance evaluation in different scenario, and the results show that plan-ahead is a desirable strategy when conducting VI mapping in the presence of VI upgrade.     

Improving survivability for multi-link failures with reprovisioning in WDM mesh networks

This article proposes a new heuristic algorithm, called Shared Multi-sub-backup-paths Reprovisioning (SMR), to improve the survivability for multi-link failures in WDM mesh networks. In SMR, each connection will be initially assigned one primary path, one backup path, and multiple sub-backup paths. When failures occur, based on the corresponding policy SMR will reprovision the primary or backup resources for these connections affected by the failures. Compared to previous algorithms, the survivable performance of SMR can be significantly improved. The short version of this article was presented at the International Workshop on Broadband Convergence Networks (BCN) 2007.     

Experimental demonstration of remote unified control for OpenFlow-based software-defined optical access networks

Passive optical network (PON) has attracted much attention by the emergence of high-bitrate video-centric applications over the Internet in the access side. In the current commercial PON, the configuration of optical line termination equipment is needed to modify through network management system manually and periodically in the local areas. The traffic flow of different users lacks dynamic control and intelligent schedule. In this paper, we propose and implement a novel software-defined optical access network (SDOAN) architecture for remote unified control based on OpenFlow-enabled PON. Based on the proposed architecture, a service-aware flow scheduling strategy is introduced to flexibly and efficiently allocate the network bandwidth resources and detect the status of network flows in real time. The SDOAN can enhance the resource utilization and QoS guarantee of each user effectively through unified control manner, and reduce the operating expense by remote interaction and operation. We have designed and verified experimentally SDOAN on our test bed with OpenFlow-enabled OLTs. The overall feasibility and efficiency of the proposed architecture are also experimentally demonstrated and compared with interleaved polling with adaptive cycle time strategy in terms of resource occupation rate and average delay.     

软件定义卫星光网络蚁群优化波长路由技术

针对卫星光网络中网络拓扑动态时变和业务类型多样化的问题,研究了在软件定义网络架构下保障服务质量的路由技术,提出了一种基于多业务的卫星光网络蚁群优化波长路由算法。通过改进蚁群算法的启发函数,将波长空闲率、时延、时延抖动、丢包率作为蚂蚁选路的重要依据,为业务选择了满足多种服务质量的最优路径;采用分组波长分配方法对不同等级的业务进行了区分服务,为不同业务分配了不同的波长集。仿真结果表明:与CL-ACRWA算法和Dijkstra算法相比,降低了卫星光网络的平均时延、平均时延抖动、平均丢包率,提高了波长利用率,同时也降低了高优先级业务的网络拥塞概率。     

Design protection for WDM optical networks

With wavelength division multiplexing (WDM) networks the failure of a single link or component may cause the simultaneous failure of several optical channels, potentially making impossible restoration by rerouting directly in higher layers directly using the optical network (SDH, ATM, internal protocol (IP)). To address this, we introduce the concept of design protection, which aims at making such failure propagations impossible. We present the disjoint alternate path (DAP) algorithm which places optical channels in order to maximize design protection. We show the result on various network examples     

SDON中基于贝叶斯模型的流量预测机制

SDON(软件定义光网络)是光网络发展的最新趋势。为了进一步提高 SDON 的智能化和对业务的动态支持,利用短期的业务流量特性预测较为长期的流量显得日益重要。文章提出了一种基于贝叶斯模型的流量预测机制,该机制充分利用贝叶斯模型对 SDON的业务流量进行长期预测。仿真结果验证了该机制的准确性和有效性。     

Time-sensitive software-defined networking (Ts-SDN) control architecture for flexi-grid optical networks with data center application

Data center interconnected by flexi-grid optical networks is a promising scenario to meet the high burstiness and high bandwidth requirement of data center application, because flexi-grid optical networks can allocate spectral resources for applications in a dynamic, tunable and efficient control manner. Meanwhile, as centralized control architecture, the software-defined networking (SDN) enabled by OpenFlow protocol can provide maximum flexibility for the networks and make a unified control over various resources for the joint optimization of data center and network resources. Time factor is firstly introduced into SDN-based control architecture for flexi-grid optical networks supporting data center application. A traffic model considering time factor is proposed, and a requirement parameter, i.e., bandwidth-period product is adopted for the service requirement measurement. Then, time-sensitive software-defined networking (Ts-SDN)-based control architecture is designed with OpenFlow protocol extension. A novel deadline-driven PCE algorithm is proposed for the deadline-driven service under Ts-SDN-based control architecture, which can complete data center selection, path computation and bandwidth resource allocation. Finally, simulation results shows that our proposed Ts-SDN control architecture and deadline-driven PCE algorithm can improve the application and network performance to a large extent in blocking probability.     

一种改进的多域光网络保护机制

生存性是保证业务服务质量的关键,多域光网络生存性问题中,由于存在多域间拓扑和路由信息不可见等约束,导致生存性实现较为困难.提出了将多域光网络进行逻辑聚合的思路,在此基础上分别针对域内和域间提出了非等值负载保护和M∶1保护机制.域内的非等值负载保护机制可以根据节点数以及业务量动态地分配保护路径,从而有效地提高资源利用率.     

Failure protection methods for optical meshed-ring communications networks

We study the survivability of a meshed-ring communication network that employs cross-connect switches. For WDM networks, the cross-connect switches are implemented as wavelength routers. Nodes can also provide cross-connection at the ATM VP (virtual path) level. By meshing the ring, the nodal degree of connectivity is increased as compared to a ring topology, and thus more alternative (protection) paths are available. For routing purposes, wavelength subnetworks are embedded in the topology. Nodes communicate with each other across one of the subnetworks to which both belong. We consider two types of subnetwork topologies to simplify the routing in a normal (nonfailure) situation. For each type of subnetwork, different protection methods are proposed to protect against a single link and/or nodal failure. The throughput performance of such meshed-ring networks under failure conditions is clearly superior to that achieved by (SONET) ring networks. We show that certain protection methods even result in lower values of the protection capacity as well as the protection capacity ratio (i.e., the overall capacity used under a failure divided by the total capacity) as compared to ring networks. We also present methods for constructing wavelength subnetworks to achieve single-failure protection using the minimal number of wavelengths.     

Efficient software-defined passive optical network with network coding

The huge increase in broadband service requires much more bandwidth than ever before; however, due to the cost sensitivity, it is not possible to pursue high transmission rate blindly in the access network, which requires us to consider how to improve network efficiency. In this paper, a software-defined passive optical network architecture with network coding (NC) is proposed to reduce downstream bandwidth consumption and thus increases the throughput and network efficiency. To flexibly implement the coding operation on local peer traffic, the NC pair management scheme is provided and keeps the compatibility with the current multi-point control protocol (MPCP) in a single optical line terminal (OLT). Considering the trends in OLT pooling and the requirement of smooth network upgrade, software-defined networking (SDN) techniques are applied in the NC-based passive optical networks. Through re-arranging the affiliations between the OLTs and optical network units (ONUs), the local traffic between peer ONUs will be led from non-NC-supported OLTs to NC-supported OLTs, and then the downstream efficiency will be still quite high even in a hybrid OLT pool. The experiments and evaluation results show that, the software-defined passive optical networks with NC reduce nearly 50 % occupied downstream bandwidth, when there is local traffic between peer ONUs, even in a hybrid OLT pool.     

Dynamical protection design with P-cycle parallel heuristic algorithm for optical networks

研究并总结了现有的各种自相似流量分析和预测的方法,同时采集局域网的动态流量数据,在此基础上生成自相似业务流.结合当今计算机界正在蓬勃发展中的并行计算,设计相关P圈配置并行算法,并将其应用到光网络的动态仿真中.     

Application-aware protection in DWDM optical networks

Fast recovery time and reduced resource utilization are the two main criteria for determining the quality of survivability mechanism. Now, it is well known that link-based protection and path-based protection provide, respectively, a short recovery time and reduced use of resources. To benefit from the both of these saliencies, we propose in this paper to use these mechanisms simultaneously. Indeed, demands mandating shorter recovery time will be protected using link-based protection. Meanwhile, other demands (e.g., no-critical) will be protected using path-based protection. Simulation results show that the proposed solution achieves a good trade-off between resource utilization and recovery time.     

Segment shared protection in WDM networks with partial wavelength conversion

In this paper, we propose a novel approach of survivable routing for segment shared protection (SSP) in mesh wavelength division multiplexing networks with partial wavelength conversion capability, with which spare capacity is allocated dynamically for a given working lightpath. The survivable routing process is formulated into a shortest path searching problem on the transferred graph of cycles (TGC) and wavelength graph of paths (WGP).     

支持流量疏导弹性光网络的共享保护策略

针对支持流量疏导的EON(弹性光网络),提出了一种改进的共享保护策略。改进策略针对不同粒度级别(如光隧道级和低速子载波级)的路径进行分级的共享保护,以保证对网络中隧道级路径进行隧道级保护。仿真结果表明,文章所提保护算法比传统的共享保护算法在阻塞率及资源利用率方面都有明显改善,其中业务阻塞率最大降低了0.47;在保护带G为16个频隙的情况下,资源利用率可节约10.95%。     

A study of the backup reprovisioning problem for FIPP p-cycles on WDM networks

As networks grow in size and complexity, both the probability and the impact of failures increase. The pre-allocated backup bandwidth cannot provide 100% protection guarantee when multiple failures occur in a network. In this article, we focus on how to recover the protecting capabilities of FIPP (Failure-independent path-protecting) p-cycles against the subsequent links failure on WDM networks, after recovering the working paths affected by the failure of link. Two recovering policies are designed to recover the protecting capabilities of the FIPP p-cycles if possible, unless there is no sufficient network resource. They are Cycle Recovery Policy and Path Recovery Policy. In addition, a Cycle Adjust algorithm is proposed and used to recover the affected cycles. The simulation results of the proposed methods are also given.     

The backup reprovisioning problem of NEPCs on survivable WDM networks

Protection techniques for optical networks mainly rely on pre-allocated backup bandwidth, which may not be able to provide full protection guarantee when multiple failures occur in a network. After recovering from the previous failure, if failure occurs again, unprotected or vulnerable lightpaths cannot be recovered. In this paper, the minimal backup reprovisioning (MBR) problem is studied, in which, the node-encircling protecting cycles (NEPCs) scheme is considered for single node-failure on WDM networks. The NEPC Recovery Algorithm is proposed to recover the protecting capabilities of the NEPC. Simulation results show that the performance of the proposed method is better than that of the traditional one.     

Cognitive algorithm using fuzzy reasoning for software-defined optical network

We propose a cognitive algorithm based on Fuzzy C-Means (FCM) technique for the learning and decision-making functionalities of software-defined optical networks (SDONs). SDON is a new optical network paradigm where the control plane is decoupled from the data plane, thus providing a degree of software programmability to the network. Our proposal is to add the FCM algorithm to the SDON control plane in order to achieve a better network performance, when compared with a non-cognitive control plane. In this context, we illustrate the use of the FCM algorithm for determining, in real time and autonomously, the modulation format of high-speed flexible rate transponders in accordance with the quality of transmission of optical channels. The performance of this FCM algorithm is evaluated via computational simulations for a long-haul network and compared to the case-based reasoning (CBR) algorithm, which is commonly used in optical cognitive networks. We demonstrate that FCM outperforms CBR in both fastness and error avoidance, achieving 100 % of successful classifications, being two orders of magnitude faster. Additionally, we propose a definition of cognitive optical networking and an architecture for the SDON control plane including the FCM engine.     

负载感知的低开销网络保护机制研究

为提高资源利用率和降低网络阻塞率,提出一种应用于光网络中带有负载感知(LA)的低开销保护机制,充分考虑了网络共享风险链路组(SRLG)的约束条件,建立整数线性规划(ILD)模型对共享通道保护策略与LA技术进行联合优化。仿真表明,与传统机制相比,所提出的机制能够有效地降低网络阻塞以及保护开销,使网络中的流量更加均衡。