Dynamic connection provisioning with shared protection in IP/WDM networks

Internet protocol (IP) traffic connections arrive dynamically at wavelength‐division multiplexing (WDM) network edges with low data rates compared with the wavelength capacity, availability, and quality‐of‐service (QoS) constraints. This paper introduces a scheme to be integrated into the control and management plane of IP/WDM networks to satisfy the availability and QoS required for IP traffic connections bundled onto a single wavelength (lightpath) in WDM networks protected by shared‐backup path protection (SBPP). This scheme consists of two main operations: (i) routing multi‐granular connections and traffic grooming policies, and (ii) providing appropriate shared protection on the basis of subscribers’ service‐level agreements in terms of data rate, availability, and blocking probability. Using the Markov chain process, a probabilistic approach is developed to conceive connection blocking probability models, which can quantify the blocking probability and service utilization of M:N and 1:N SBPP schemes. The proposed scheme and developed mathematical models have been evaluated in terms of bandwidth blocking ratio, availability satisfaction rate, network utilization, and connection blocking probability performance metrics. The obtained research results in this paper provide network operators an operational setting parameter, which controls the allocation of working and backup resources to dynamic IP traffic connections on the basis of their priority and data rate while satisfying their requirements in terms of bandwidth and availability. Copyright © 2013 John Wiley & Sons, Ltd.     

On-line integrated routing in dynamic multifiber IP/WDM networks

This paper focuses on dynamic integrated routing in multifiber Internet protocol/wavelength-division multiplexing (IP/WDM) networks, which can be implemented through either one-step routing (OSR) or two-step routing (TSR) approach. Based on an extended layered-graph, two resource assignment strategies, termed channel-level balance (CLB) and link-level balance (LLB), are proposed to balance the traffic in the network at different levels. To further improve the performance, a parameter K is introduced to make a dynamic tradeoff between the logical-layer links and the optical-layer links. Simulation studies are carried out for various topologies. The results show that LLB is better than CLB in most cases, and LLB combined with OSR has the optimal performance. Also, we find that the routing approach and the resource assignment strategy individually play different roles with different values of r/sub l/ that is introduced to indicate the resource richness of the network. As a multifiber network is functionally equivalent to a single-fiber network with limited wavelength conversion, we investigate the effects of wavelength conversion by studying the multifiber IP/WDM networks. The analysis shows that, when the granularity of each connection request is much smaller than the wavelength granularity, wavelength conversion may increase the request blocking probability in the network.     

Power-aware provisioning strategy with shared path protection in optical WDM networks

As the Internet continues to grow, the power consumption of telecommunication networks is rising at a considerable speed, which seriously increases the operational expenditure and greenhouse gas emission. Since optical Wavelength Division Multiplexing (WDM) networks are currently the most promising network infrastructures, power saving issue on these networks has received more attention in recent years. In traditional optical WDM networks, a large amount of power is drained by the redundant idle resources and reserved backup resources although these powered on resources do not carry traffic in most of the time. In order to reduce the network power consumption, turning off the corresponding network components or switching them to a low-power, standby state (or called sleep mode) is a promising greening approach. In this paper, we study the power-aware provisioning strategies and propose a sleep mode based Power-Aware Shared Path Protection (PASPP) heuristic algorithm to achieve the power efficiency of optical WDM networks. By jointly utilizing link-cost and fiber-cost in path routing, resource assignment, and resource release, PASPP makes working paths and backup paths converge on different fibers as much as possible, and switch idle and backup components to sleep mode to realize power saving. Simulation results show that our PASPP can obtain notable power saving and achieve satisfactory tradeoff between power efficiency and blocking probability with respect to Power-Unaware Shared Path Protection (PUSPP).     

Path-based routing provisioning with mixed shared protection in WDM mesh networks

In this paper, the authors focus on studying the problem of survivable routing provisioning to prevent single link failure in wavelength-division-multiplexing (WDM) mesh networks, and propose a novel protection scheme called mixed shared path protection (MSPP). With MSPP, the authors define three types of resources: 1) primary resources that can be used by primary paths; 2) spare resources that can be shared by backup paths; and 3) mixed resources that can be shared by both the primary and the backup paths. In the proposed protection scheme, each connection is assigned a primary path and a link disjoint backup path. Differing from pervious protection schemes, MSPP allows some primary paths and backup paths to share the common mixed resources if the corresponding constraints can be satisfied. In this paper, the authors consider three types of path-based protection schemes, i.e., dedicated path protection (DPP), shared path protection (SPP), and MSPP, and evaluate their performance for both the static and the dynamic provisioning problems. Simulation results show that MSPP outperforms DPP and SPP.     

Performance evaluation of p-cycle based protection methods for provisioning of dynamic multicast sessions in mesh WDM networks

Network survivability is crucial to both unicast and multicast traffic. Up to now, extensive research has been done on unicast traffic protection. Recently, due to the rapid growth of multicast applications, such as video-conferencing, high definition television (HDTV), distance learning, and multi-player on-line gaming, the problem of multicast traffic protection has started to draw more research interests. The preconfigured protection cycle (p-cycle) method proposed by Grover offers fast speed in restoration (because p-cycles are pre-cross-connected) and high efficiency in resource utilization (because p-cycles protect both on-cycle and straddling links). So far p-cycles based protection approaches have been intensively studied for unicast traffic protection, but have been rarely investigated for multicast traffic. We propose to apply p-cycles to dynamic protection provisioning of multicast traffic, and evaluate the blocking performance in comparison to other existing multicast protection schemes. We consider three different p-cycle based multicasting protection methods, namely dynamic p-cycle (DpC) design, p-cycle based protected working capacity envelope (PWCE) design, and hybrid DpC and PWCE design. We show that p-cycle-based multicast protection approaches offer much better blocking performance, as compared with other existing multicast protection schemes. The main reasons for the much better blocking performance are attributed to the facts that (i) the selection of p-cycles is independent of the routing of the multicast light trees, (ii) there are no path/segment disjoint constraints between the selected p-cycles and the multicast light trees to be protected, (iii) the selected p-cycles are the most efficient p-cycles.

IP/WDM网络中的链路保护路由算法研究

基于IP/WDM网络的对等模型,在联合路由的基础上,对SRLG约束的联合共享链路保护机制的路由选择与资源分配算法进行了研究,并提出了一种新的MI-APF-ISLP算法.为了验证该算法的有效性,以自相似和Poisson模型两种业务模型为基础,将连接阻塞概率CBP和带宽吞吐率BTP作为性能指标,在不同参数条件下进行动态仿真,结果表明MI-APF-ISLP算法要优于传统算法.     

WDM光网络中一种新型的动态共享保护算法

波分复用(WDM)光网络中引入了共享风险链路组(SRLG)的概念 ,要求工作通路与保护通路不能处于同一个SRLG之中.文章提出了一种基于SRLG限制的动态共享通道保护算法,即满足K对业务的动态链路权重配置(K-Dynamic Link Weight Configuration, K-DLWC)算法 ,该算法的     

A novel 1:N protection scheme for WDM passive optical networks

This paper presents a 1:N protection scheme based on the cyclic property of an array waveguide grating and a specific connection pattern among the optical network units (ONUs). The proposed scheme requires half the number of wavelengths of existing schemes presented in the literature. Although the current scheme requires more fiber links among the ONUs than previous schemes, the network resource demands are greatly reduced and the protection performance is improved.     

Survivable lightpath provisioning in WDM mesh networks under shared path protection and signal quality constraints

This paper addresses the problem of survivable lightpath provisioning in wavelength-division-multiplexing (WDM) mesh networks, taking into consideration optical-layer protection and some realistic optical signal quality constraints. The investigated networks use sparsely placed optical-electrical-optical (O/E/O) modules for regeneration and wavelength conversion. Given a fixed network topology with a number of sparsely placed O/E/O modules and a set of connection requests, a pair of link-disjoint lightpaths is established for each connection. Due to physical impairments and wavelength continuity, both the working and protection lightpaths need to be regenerated at some intermediate nodes to overcome signal quality degradation and wavelength contention. In the present paper, resource-efficient provisioning solutions are achieved with the objective of maximizing resource sharing. The authors propose a resource-sharing scheme that supports three kinds of resource-sharing scenarios, including a conventional wavelength-link sharing scenario, which shares wavelength links between protection lightpaths, and two new scenarios, which share O/E/O modules between protection lightpaths and between working and protection lightpaths. An integer linear programming (ILP)-based solution approach is used to find optimal solutions. The authors also propose a local optimization heuristic approach and a tabu search heuristic approach to solve this problem for real-world, large mesh networks. Numerical results show that our solution approaches work well under a variety of network settings and achieves a high level of resource-sharing rates (over 60% for O/E/O modules and over 30% for wavelength links), which translate into great savings in network costs.     

A balancing scheme for QoS-aware service provisioning in OPS networks

The service level agreement (SLA) specifies the service availability that a service provider promises to a customer. Through introducing SLA into optical packet switching networks, a balancing scheme for quality of service-aware service provisioning is proposed, which uses packet loss ratio as availability index to obtain a larger number of SLA-satisfied services and achieve a better balance among different level services by means of discarding packets with better packet loss capacity in priority to fully make use of the capacity of services themselves. The theoretical analysis and simulation results show that the proposed scheme outperforms the other two typical service provisioning schemes in terms of the above two aspects.     

Dynamic circuit provisioning in all-optical WDM networks using lightpath switching

In this paper we investigate the problem of provisioning holding-time-aware (HTA) dynamic circuits in all-optical wavelength division multiplexed (WDM) networks. We employ a technique called lightpath switching (LPS) wherein the data transmission may begin on one lightpath and switch to a different lightpath at a later time. Lightpath switches are transparent to the user and are managed by the network. Allowing LPS creates a number of segments that can use independent lightpaths. We first compare the performance of traditional routing and wavelength (RWA) assignment to routing and wavelength assignment with LPS. We show that LPS can significantly reduce blocking compared to traditional RWA. We then address the problem of routing dynamic anycast HTA dynamic circuits. We propose two heuristics to solve the anycast RWA problem: anycast with continuous segment (ACS) and anycast with lightpath switching (ALPS). In ALPS we exercise LPS, and provision a connection request by searching for the best candidate destination node is such a way that the network resources are utilized efficiently. In ACS we do not allow a connection request to switch lightpaths. The lightpaths to each candidate destination node of a request are computed using traditional RWA algorithms. We first compare the performance of ACS to ALPS and observe that ALPS achieves better blocking than ACS. Furthermore, we also compare the performance of these two anycast RWA algorithms to the traditional unicast RWA algorithm. We show that the anycast RWA algorithms presented here significantly outperform the traditional unicast RWA algorithms.     

An online cost-efficient protection scheme for quick recovery in all-optical WDM mesh networks

Since a single fiber carries a huge amount of data in optical WDM networks, a fiber cut even for a brief period is a very serious event. Designing schemes to prevent disruption of user traffic and recovery techniques from failures is thus an important area of research. Since a single fiber cut is the most common type of fault, in this paper we address the problem of protecting all-optical WDM mesh networks from single link failure. Our proposed online protection scheme is an improvement over an existing approach and is not only cost-efficient in terms of network resource consumption but can also provide quick recovery from a link failure. We first provide an ILP formulation for the problem and then propose a heuristic solution iStreams that can provide near-optimal solution in polynomial time. Performance comparisons with some well-known schemes of protection show that our heuristic algorithm can be a better choice for conserving resource while providing quick recovery from a link failure.     

Tbit/s switching scheme for ATM/WDM networks

A new high capacity, reservation-based switch architecture for ATM/WDM networks is presented. The scheme is contention-free and highly flexible yielding a powerful solution for high-speed broadband packet-switched networks. Switching management and control are studied for data rates of up to 10 Gbit/s/port, providing and aggregated throughput of over 1 Tbit/s     

Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.     

IP over WDM网络联合恢复策略的研究

文章对动态自相似业务在多纤IP over WDM 网中的联合恢复问题进行了系统的研究,提出了3种联合恢复策略,算法的实现基于一种扩展的多纤分层图模型.通过大量的动态仿真实验,以业务中断率和恢复效率为性能指标,研究了上述3种恢复策略在不同自相似参数(突发度、均值和方差)中的性能,最后通过分析和比较得出联合通道恢复策略是最优的.     

Shared protection in mesh WDM networks

This article introduces the design principles and state-of-the-art progress in developing survivable routing schemes for shared protection in mesh WDM networks. This article first gives an overview of the diverse routing problem for both types of protection in mesh networks, path-base and segment shared protection; then the cost function and link state for performing diverse routing are defined by which the maximum extent of resource sharing can be explored in the complete routing information scenario. Review is conducted on the most recently reported survivable routing schemes along with state-of-the-art progress in diverse routing algorithms for segment shared protection. The following three reported algorithms are discussed in detail: iterative two-step-approach, potential backup cost, and maximum likelihood relaxation.     

Online connection provisioning in metro optical WDM networks using reconfigurable OADMs

Optical add/drop multiplexers (OADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) ring networks by allowing traffic to bypass intermediate nodes without expensive opto-electro-opto (O-E-O) conversion. Some traditional OADMs, called fixed OADMs (FOADMs), can only add/drop traffic on a specific wavelength. Reconfigurable OADMs (ROADMs) are emerging, which can add/drop traffic onto/from different wavelengths at different time. ROADMs provide desirable flexibility, enable fast provisioning of dynamic traffic, and save capital expenditure (CapEx) and operational expenditure (OpEx). In order to be cost effective, some ROADMs employ architectures that tune the ROADM continuously from one wavelength to another, crossing through all the wavelengths in between, which may cause interference to the connections, if any, on those wavelengths being crossed. In order to prevent existing connections from being interrupted, a constraint needs to be imposed that ROADMs cannot cross working wavelengths when tuning. In this paper, the design and the benefits of metro optical WDM network architectures using ROADMs and the impact of this tuning constraint on the performance of the network are investigated. The dynamic traffic provisioning problem is analyzed and divided into two subproblems: 1) a traditional one on resource allocation; and 2) a new subproblem on tuning-head positioning (TP). Several heuristics for each subproblem are developed to combat the tuning constraint. Results from our simulation experiments show that the tuning constraint can significantly affect the network performance in terms of overall connection blocking probability, and good heuristics for network control and management are needed to overcome this tuning constraint.     

Dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes

The wavelength selective switch-based reconfigurable optical add/drop multiplexers is a promising switching equipment for future reconfigurable wavelength-division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment problem. In an asymmetric switching scenario, using the classic Dijkstra’s algorithm can lead to invalid paths traversing unconnected ports of an asymmetric node. To solve this problem, we propose both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes. The proposed LS schemes include the asymmetric switching-aware (ASA) Dijkstra’s algorithm, the $K$ -shortest path-based algorithm, and the entire path searching (EPS) algorithm. Simulation results show that the ASA-Dijkstra’s algorithm will bring notable improvement of the blocking performance with low computational complexity, while the EPS algorithm has much higher complexity and is not suitable to be employed in large-scale networks. On the other hand, our proposed DV solution, i.e., the information diffusion-based routing (IDBR), can achieve the lowest blocking probability with the lowest computational complexity. Moreover, IDBR does not require the distribution of local asymmetric switching information like the LS schemes, thus having a high level of topology confidentiality.     

Optical multicast provisioning with differentiated leaf availability guarantee in WDM networks

As multicast applications become more and more popular, implementing multicast in the optical domain has attracted increased attention due to its more efficient bandwidth usage. And also these services have quality-of-service requirements. In this article, the problem of cost-effective optical multicast provisioning to satisfy the differentiated leaf availability requirements is formally stated. A Mixed Integer Linear Program formulation is proposed for provisioning dedicated light-tree protection with differentiated leaf availability guarantee. The algorithm is so complex and infeasible that we also propose a feasible two-step approximate approach to solve the problem. Different from the previous schemes, our scheme finds out the primary light-trees and backup paths for destination nodes whose availability is not satisfied. Because of taking the different leaf availability requirements into account, the proposed algorithm obtains a more efficient feasible solution requiring less network resources.     

基于GMPLS的LSP的双重保护和恢复机制

主要探讨了基于GMPLS技术的LSP的双重保护机制.首先描述了LSP的双重保护机制的含义,然后重点分析了LSP的双重保护机制涉及的问题及具体的实现过程,最后,通过仿真得出结论,说明该保护机制的优越性.