智能光网络的多域生存性技术研究

自动交换光网络是传送网的发展趋势,而快速高效的生存性是其重要特点.介绍了光网络生存性,重点分析了多域网络和域间路由问题,并且提出了具体的实现多域网络的生存性方法.     

光网络中基于路径计算单元的路由机制研究

针对大规模多层多域光网络群故障发生时的网络受损情况,提出基于路径计算单元(PCE)架构的跨域路由算法进行快速恢复,并基于OMNet平台对多层多域路由方案进行了性能仿真分析。结果表明,基于PCE架构的路由策略在群故障发生时能够大大减少网络中的路径计算请求泛洪信息,降低路由计算收敛时间,可以提高全网剩余资源的资源利用率,为业务的快速恢复提供了路由基础。     

A novel multi-link fault-tolerant algorithm for survivability in multi-domain optical networks

With the large-scale deployment of optical network equipments, the problems of separated domains management and the multi-domain-based survivability have become the primary challenge in new generation intelligent optical networks. Aimed at resisting multi-link failures in multi-domain optical networks (MDON), a heuristic multi-link fault-tolerant (MLFT) algorithm for survivability in MDON is proposed in this article, which applied Hamiltonian cycle protection and segment-shared protection to establish a novel survivability strategy for either intra-domain??s or inter-domain??s multiple links, respectively. Furthermore, a new virtual-link mapping scheme and link-cost formulas are presented to encourage the appropriate routing selection and load balancing, which can also contributed to better resource utilization ratio and blocking ratio. Simulation results show that MLFT realizes the multi-link fault-tolerant survivability at a lower cost with better performances in redundancy ratio, blocking ratio, and computation complexity.     

A novel domain-by-domain survivable mechanism in multi-domain wavelength-division-multiplexing optical networks

In multi-domain wavelength-division-multiplexing (WDM) optical networks, the inter-domain routing is a challenge since each single-domain cannot view the full network topology. At the same time, survivability is also an important issue in optical networks since the failures of fiber links or network nodes may lead to a lot of traffic being blocked. In this paper, we study the survivability in multi-domain WDM optical networks, and propose a new survivable mechanism called load balanced domain-by-domain routing (LBDDR). In LBDDR, in order to obtain the efficient inter-domain survivable routes, we present the domain-by-domain routing (DDR) method which can find the intra-domain sub-working path and sub-backup path in each single-domain to form the inter-domain working path and backup path for each demand. In order to reduce the blocking probability, we present the load balanced routing method which can encourage the traffic to be uniformly distributed on the links with more free wavelengths. Simulation results show that, compared with conventional mechanism, LBDDR can obtain better performances.     

基于NS2多域ASON仿真平台设计与实现

对一个基于单域ASON仿真平台扩展实现了多域ASON仿真平台.通过对网络节点Id进行分域,实现了ASON中的多域分层网络结构,引入了一种基于全网抽象的路由信息汇聚策略.在ASON网络的分层路由中的每个路由域中加入备份Speaker节点,使网络具有更好的生存性.仿真测试表明当网络规模较大时,多域ASON网络在拓扑收敛速度、连接建立时间等方面的性能均优于单域.     

Evaluation of post-fault restoration strategies in multi-domain networks

Although multi-domain survivability is a major concern for operators, few studies have considered the design of post-fault restoration schemes. This paper proposes two such strategies, based upon hierarchical routing and signaling crankback, to handle single and multi-link failure events in multi-domain IP/MPLS networks (also extendible to optical DWDM networks). Specifically, the hierarchical routing strategy relies upon abstracted domain information to compute inter-domain loose routes, whereas the crankback scheme applies signaling re-tries to restore paths in a domain-by-domain manner. The performance of these proposed solutions is then analyzed and compared via simulation.     

多域光网络联合路由保护算法

研究了多域光网络中的路由保护问题。为了避免多域光网络通路保护二步算法可能导致的多域陷阱问题,提出了一种基于Suurballe算法扩展的多域联合路由保护算法。仿真表明,相比传统的多域通路保护二步算法,该算法资源利用率高,阻塞率低,平均每连接跨域数小。     

Rate control-based framework and algorithm for optimal provisioning

Ideally, networks should be designed to accommodate a variety of different traffic types, while at the same time maximizing its efficiency and utility. Network utility maximization (NUM) serves as an effective approach for solving the problem of network resource allocation (NRA) in network analysis and design. In existing literature, the NUM model has been used to achieve optimal network resource allocation such that the network utility is maximized. This is important, since network resources are at premium with the exponential increase in Internet traffic. However, most research work considering network resource allocation does not take into consideration key issues, such as routing and delay. A good routing policy is the key to efficient network utility, and without considering the delay requirements of the different traffic, the network will fail to meet the user’s quality of service (QoS) constraints. In this paper, we propose a new NUM framework that achieves improved network utility while taking into routing and delay requirements of the traffic. Then, we propose a decomposition technique-based algorithm, D-NUM, for solving this model efficiently. We compare our approach with existing approaches via simulations and show that our approach performs well.     

Multi-Layer Differentiated Integrated Survivability for Optical Internet

In this paper, we study the problem of multi-layer integrated survivability (MLIS) for efficiently provisioning reliable traffic connections of arbitrary bandwidth granularities in the integrated optical Internet. We decompose the MLIS problem into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCD), and dynamic survivable routing (DSR). First, a review of network survivability in multi-layer IP/WDM networks is provided. Then, multi-layer survivability strategies are proposed and it is observed how these strategies could be applied to the integrated optical Internet architecture. We also present an enhanced integrated shared pool (ISP) method for solving the static MLIS problem (i.e., the SCD sub-problem) and the priority-based integer programming formulations are also given. Moreover, we design a novel scheme called the differentiated integrated survivability algorithm (DISA) to solve the dynamic MLIS problem (i.e., the DSR sub-problem), which employs flexible survivable routing strategies according to the priority of the traffic resilience request. Performance simulation results of DISA show that our adaptive survival schemes perform much better in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio compared with other solutions in the optical Internet.     

多域光网络生存性的关键技术研究

多域光网络的生存性作为衡量网络性能优劣的关键指标,与实际网络应用的关系最为密切,是当前迫切需要解决的关键问题;聚焦高速化、多业务化驱动的多域光网络环境下的生存性技术.基于光网络的多业务、分布式控制的特性,分析了多域光网络生存性机制的研究现状及面临的挑战;给出了一种针对多域光网络生存性问题的分类方法;结合多域光网络对生存性的需求,对相关关键技术进行了归类和研究,并指明了进一步研究的方向和重点.     

A novel Topology Aggregation approach for shared protection in multi-domain networks

Routing for shared protection in multi-domain networks is more difficult than that in single-domain networks because of the scalability requirements. We propose a novel approach for shared protection routing in multi-domain networks where the key feature is a special Topology Aggregation. In this Topology Aggregation, only some potential intra-domain paths (intra-paths for short) are selected for carrying working and backup traffic between domain border nodes. The abstraction of each intra-path to a virtual edge makes the original multi-domain network to become an aggregated network. On the aggregated network, a single-domain routing algorithm for shared protection can be applied for obtaining the complete routing solutions. The experiments show that the proposed approach is scalable. Moreover it is close to the optimal solution in single-domain networks and outperforms the previously proposed scalable solutions in multi-domain networks.     

Surviving double-link failures for near optimal heuristic routing in protected optical networks

The survivability for double-link failures in WDM optical network has been studied in recent years. In previous algorithm, to survive the double-link failures each connection request will be assigned to one primary path and two link-disjoint backup paths. However, the previous algorithm is the so-called simple algorithm which may lead to low resources utilization and high blocking probability. In this paper, we propose a new heuristic algorithm called routing with optimal solution (ROS) to protect the double-link failures. Differing from the previous algorithm, ROS can obtain near optimal solution by recomputing the primary path and two backup paths based on the rerouting policy for each connection request. Simulation results show that ROS can significantly outperform the previous algorithm.     

Survivability in multi-domain optical networks using p-cycles

Survivability is becoming an important issue in optical networks due to the huge bandwidth offered by optical technology. Many works have studied network survivability. The majority of these works are destined for single-domain networks. In this work, we address the survivability of multi-domain optical networks. This paper provides a classification of the existing protection solutions proposed for multi-domain networks and analyses their advantages and limitations. We propose a new solution for multi-domain optical networks based on p-cycles (pre-configured cycles). For scalability and security reasons, we also propose a topology aggregation model adapted to p-cycle computations. This aggregation model allows our proposed solution to find a trade-off between two competing goals: efficient use of backup resources and short running time. Simulation results show that the proposed solution is a good trade-off between resource utilization and running time compared to existing solutions.     

A novel method to evaluate clustering algorithms for hierarchical optical networks

The routing issues in multi-layer and multi-domain optical networks have drawn much attention in current research. With the introduction of the path computation element, routes can be calculated more efficiently in multi-domain optical networks. However, the optimal degree of routing approach in multi-layer and multi-domain optical networks is also determined by the clustering algorithms deployed for construction of hierarchical networks. Therefore, it is important to investigate the way to evaluate the impact of the clustering algorithm on the routing approach (e.g., blocking probability) in optical networks with dynamic traffic, which has not been studied sufficiently. In this paper, a novel method to describe and evaluate the clustered structures generated by different clustering algorithms for hierarchical optical networks is proposed. This method deploys a novel evaluation metric that represents blocking probability of clustered optical networks, so it can be used as guidelines for designing clustered structures. Besides theoretical analysis, simulations are carried out on different network topologies and clustered types to validate the effectiveness of the method presented.     

自动交换光网络中恢复路径提供机制的研究

为了获得高效的网络生存性能,基于自动交换光网络(ASON)的框架,该文提出了一种新型的可恢复路径选择算法-联合可变权重可恢复路径(JVWR)选择算法,并进行了数值仿真分析,仿真结果表明,此恢复路径选择算法具有明显的业务量均衡能力,并降低了动态连接请求的阻塞概率,同时具有良好的带宽利用率和恢复资源共享效率。该文还对mesh网络业务路径和恢复路径的建立机制进行了讨论,在ASON功能框架之内,基于通用多协议标记交换提出了并行mesh共享恢复路径建立机制,从而较系统地对分布式恢复路径动态建立机制进行了研究。     

Selective survivability with disjoint nodes and disjoint lightpaths for layer 1 VPN

This paper deals with the problem of survivable routing and wavelength assignment in layer 1 virtual private networks (VPNs). The main idea is routing the selected lightpaths by the layer 1 VPN customer, in a link-disjoint manner. The customer may freely identify some sites or some connections, and have their related lightpaths routed through link-disjoint paths through the provider’s network. This selective survivability idea creates a new perspective for survivable routing, by giving the customer the flexibility of selecting important elements (nodes or connections) in its network. This study is different from previous studies which aim to solve the survivable routing problem for the whole VPN topology. The proposed scheme is two-fold: disjoint node based, and disjoint lightpath based. In disjoint node scheme, all lightpaths incident to a node are routed mutually through link-disjoint paths. In disjoint lightpath scheme, a lightpath is routed in a link-disjoint manner from all other ligthpaths of the VPN. We present a simple heuristic algorithm for selective survivability routing. We study the performance of this algorithm in terms of resources allocated by the selective survivability routing scheme compared to shortest path routing with no survivability. The numerical examples show that the amount of used resources by the selective survivability scheme is only slightly more than the amount used in shortest path routing, and this increase is linear. The extra resources used by the new scheme are justified by better survivability of the VPN topology in case of physical link failures, and the simplicity of the implementation.     

Distributed dynamic grooming routing and wavelength assignment in WDM optical mesh networks

The bandwidth of a wavelength channel in WDM optical networks is very high compared to the user’s requirements for various applications. Therefore, there is a scope for better utilization of channel bandwidth by traffic grooming, in which several user’s channels are multiplexed for transmission over a single channel. Several research works have been reported on traffic grooming routing and wavelength assignment (GRWA) for static and dynamic traffic pattern under centralized environment. Distributed dynamic grooming routing and wavelength assignment (DDGRWA) is a new and quite unexplored area in WDM optical mesh networks. This article introduces the concept of distributed traffic grooming in WDM mesh networks which also includes virtual topology construction, reconfiguration, routing and wavelength assignment in the distributed environment assuming incoming traffic to be dynamic in nature. We have also presented simulation results of our algorithm on dynamically generated traffic under various network topologies.     

Multicast service protection algorithm based on elastic optical network

With the rapid growth of the network traffic,the elastic optical network (EON) has been proposed as a promising solution due to its high spectrum efficiency and flexible bandwidth provision.Meanwhile,multicast routing and spectrum allocation,and the survivability of the network become more challenging than that in the conventional optical network.The routing for multicast traffic and its protection algorithm in EON was investigated.An integer linear programming (ILP) formulation with the objective to minimize total spectrum consumption was presented.In addition,a heuristic algorithm called multicast sub-tree protection algorithm (MSPA) to achieve sufficient protection and satisfy resources savings was designed.The simulation results demonstrate that comparing with the traditional multicast routing and protection algorithm,MSPA performs well in improving the blocking probability and the spectrum utilization of the network.     

Towards Robust Multi-Layer Traffic Engineering: Optimization of Congestion Control and Routing

In the Internet today, traffic engineering is performed assuming that the offered traffic is inelastic. In reality, end hosts adapt their sending rates to network congestion, and network operators adapt the routing to the measured traffic. This raises the question of whether the joint system of congestion control (transport layer) and routing (network layer) is stable and optimal. Using the established optimization models for TCP and traffic engineering as a basis, we find the joint system can be stabilized and often maximizes aggregate user utility. We prove that both stability and optimality of the joint system can be guaranteed for sufficiently elastic traffic simply by tuning the cost function used for traffic engineering. Then, we present a new algorithm that adapts on a smaller timescale to changes in traffic distribution and is more robust to large traffic bursts. Uniting the network and transport layers in a multi-layer approach, this algorithm, distributed adaptive traffic engineering (DATE), jointly optimizes the goals of end users and network operators and reacts quickly to avoid bottlenecks. Simulations demonstrate that DATE converges quickly     

基于Grover搜索算法的MANET网络路由协议

In Mobile Ad-hoc Networks (MA-NETs), routing protocols directly affect various indices of network Quality of Service (QoS), so they play an important role in network performance. To address the drawbacks associated with traditional routing protocols in MANETs, such as poor anti-fading perfor-mance and slow convergence rate, for basic Dynamic Source Routing (DSR), we propose a new routing model based on Grover’s sear-ching algorithm. With this new routing model, each node maintains a node vector function, and all the nodes can obtain a node probability vector using Grover’s algorithm, and then select an optimal routing according to node probability. Simulation results show that compared with DSR, this new routing protocol can effectively extend the network lifetime, as well as reduce the network delay and the number of routing hops. It can also significantly improve the anti-jamming capa-bility of the network.