WDM网状网络中一种动态多播自适应业务疏导算法

光多播业务需要消耗大量的WDM光网络带宽资源,业务疏导是光多播网络降低业务请求阻塞率和提高带宽资源利用率的有效方法。提出了一种新型光多播疏导节点结构,研究了疏导端口优先的多播业务疏导算法(TGPFA)和新建光树优先的多播业务疏导算法(TCLFA),进而提出了一种能够适应网络资源变化的动态多播业务疏导算法(ADMGA)。结果表明,在网络资源有限的情况下,ADMGA算法能取得较低的请求阻塞率和带宽阻塞率,获得较好的网络性能。     

网状WDM网中多播业务的共享保护设计

研究网状波分复用(WDM)光网络中动态多播业务的保护方案,提出一种共享保护和重配置(SPR)算法.该算法根据网络状态动态调整链路代价,为每个多播业务请求建立最小代价工作树,并为光树上互不重叠的工作段提供链路分离的保护段.当网络中发生链路失效时,进行业务段保护切换和局部资源重配置.仿真表明,该算法可以合理共享波长资源、平衡网络负载,有效保护WDM网中任意单链路失效,并在多链路失效情况下大大提高业务恢复能力.     

弹性光网络中面向任播业务的节能路由算法

为提高数据中心间光互联网络的能效,面向任播业务提出一种具有业务持续时间感知的混合路径传输节能路由算法.为了减少新建光路和工作元器件数量,优先采用单路径传输;若业务阻塞则以传输能耗最小化为目标进行多路径传输.除此之外,引入基于频谱预留的业务疏导策略来降低保护带宽和光收发器的开销.仿真结果表明:与传统节能路由算法相比,所提算法在显著降低网络能耗的同时,有效避免了业务阻塞率的过度增加,实现了网络能耗与性能的平衡.     

WDM格型光网络中的动态组播共享保护算法

该文针对WDM格型网络中单链路失效的情况,提出了一种保护动态组播业务的基于路径的优化共享保护(PB-OSPM)算法。该算法在基于最优路径对的共享不相交路径(OPP-SDP)算法的基础上,通过引入保护波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,允许不发生冲突的不同组播的保护路径间共享预留波长资源。研究采用欧洲光网络(EON)的拓扑对PB-OSPM算法和OPP-SDP算法在增性网络负载情况下的网络冗余度和同波长资源配置和网络负载情况下动态网络负载的网络连接阻塞率做了仿真。结果表明,相同条件下,PB-OSPM算法比OPP-SDP算法有更低的连接阻塞率。组播业务间波长资源的共享是提高波长资源利用率的有效方法。     

弹性光网络双重故障下的自适应保护级别算法

为了降低弹性光网络中双链路故障保护下的业务及带宽阻塞率、均衡带宽资源分配,提出了一种双重故障下的自适应保护级别算法。该算法综合考虑传输距离、调制格式等因素,根据链路频谱资源使用状态动态地更新链路惩罚系数,选取最佳路径进行传输,同时根据请求类型及网络空闲资源状态自适应地选择保护方法,为业务提供最大限度的保护。仿真结果表明,在双链路故障下,算法在阻塞率方面取得了较好的性能,同时均衡了网络中各链路上的资源使用。     

基于层叠模型的动态组播业务疏导算法

流量疏导对于提高波分复用网络的利用率具有重要的意义.文章基于层叠模型的IP over WDM网络结构,研究了动态组播业务疏导问题,给出了两种动态组播业务疏导方法.仿真结果显示,在IP层和光层都计算最短路径来选取最短路径组建组播树的算法能够获得更低的阻塞率.     

WDM光网络中基于链路的动态组播共享保护算法

针对WDM光网络中单链路失效的情况,提出了一种基于链路的保护动态组播业务的优化共享保护算法(Link-based optimized shared-protection algorithm for multicast sessions,LB-OSPM).该算法在对工作树任意光纤链路失效情况寻找保护路径时,允许组播内不同保护路径共享预留波长资源,同时通过引入预留波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,实现了不发生冲突的不同组播的保护链路间共享预留波长资源.研究采用欧洲光网络(European Optical Network,EON)的拓扑对不同波长资源配置和网络负载情况下LB-OSPM算法的网络连接阻塞率做了仿真.结果表明,通过引入共享机制,LB-OSPM算法在对单链路失效保证100％恢复率的同时可以获得更低的连接阻塞率,提高了波长资源利用效率.     

一种面向IP/GMPLS over WDM网络的优化综合路由算法

为了优化利用IP层和WDM层网络资源,在WDM网络集成辅助图模型的基础上,提出了一种面向IP/GMPLS over WDM网络的基于代价的优化综合路由算法,即CIR(Cost-basedIntegrated Routing).该算法将IP层和WDM层资源可用信息以代价函数形式给出,并将因网络拓扑结构和网络负载分布不均衡等产生的瓶颈链路以及带宽碎片问题也统一纳入考虑,由此将LSP建立问题转化为在集成辅助图上找出一条源、目的节点之间的最短通路问题.仿真结果表明:CIR算法有效地实现了IP和WDM两层资源的联合优化,提高了网络资源利用,降低了网络阻塞率.     

网状WDM网中双链路失效的共享路径保护设计

该文研究了WDM网状网中双链路失效问题,在假定所有链路共享风险链路组(Share Risk Link Group, SRLG)分离的条件下,提出了一种动态共享路径保护(Dynamic Shared-Path Protection,DSPP)算法。DSPP能根据网络状态动态调整链路代价,为每条业务请求选择一条最小代价的工作路由和两条最小代价且SRLG分离的保护路由。仿真表明,DSPP不仅能完全保护双链路失效,并且能在资源利用率、阻塞率和保护切换时间之间进行性能折衷。     

IP over WDM网络中业务持续时间感知的绿色路由算法

研究了IP over WDM网络的低碳路由问题,综合 考虑业务持续时间和利用可再生能源和传统能源供能两个 因素,基于分层图模型,提出一种带有业务持续时间感知的绿色路由(HTAGR)算法。HTAGR 依据节点处太阳能 供能情况以及节点和链路的能耗情况动态调整链路权值,并鼓励选择业务持续时间内需要额 外消耗传统能源最少的 路径建立连接。仿真结果表明,与传统节能路由算法相比,HTAGR 有利于消耗更少的传统能 源和使用更多的可再 生能源,在保持较低阻塞率的同时,进一步降低了业务平均传统能耗和CO₂排放量。     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

An efficient dynamic multicast traffic-grooming algorithm for WDM networks

With the growth of multi-granularity multicast applications, there comes into being a huge gap between the bandwidth of a wavelength provided and a multicast traffic required in the wavelength division multiplexing (WDM) networks. The dynamic multicast traffic-grooming is an effective way for WDM networks to improve the wavelength utilization and decrease the traffic blocking probability. A novel switching node architecture with the multicast switching matrix and traffic-grooming fabric is studied in the paper. Then, an efficient dynamic multicast traffic-grooming algorithm is proposed for the architecture. According to the ratio of network available grooming port number to network transceiver number, the proposed algorithm estimates whether the traffic-grooming port is a scarce resource for input traffic and chooses the appropriate grooming strategy. If the traffic-grooming port is scarce, the minimized use grooming port strategy is designed for the coming traffic. On the contrary, the minimized use node transceiver strategy is applied for the coming traffic. Simulation results show that the proposed algorithm can groom traffic efficiently with low blocking probability and high network throughput constraint by limiting number of node transceivers and grooming ports.     

Traffic grooming in WDM optical network with grooming resources at Max Connectivity nodes

In this paper, we propose Max Connectivity grooming in WDM mesh networks under static lightpath connection requests. The grooming and wavelength conversion resources are placed at the nodes having maximum connections. We propose a heuristic genetic algorithm (GA) model to solve grooming, routing and wavelength assignment. The GA algorithm has been used to optimize the cost of grooming and wavelength conversion resources. The blocking probability has been investigated under different lightpath connections. The performance of Max Connectivity grooming has been compared with other grooming policies. Our results indicate the improvement of resource utilization with minimum blocking probability.     

An efficient mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks

This paper proposes an efficient overlay multicast provisioning (OMP) mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks. To facilitate request provisioning, OMP jointly utilizes a data learning (DL) scheme on the IP/MPLS layer for logical link cost estimation, and a lightpath fragmentation (LPF) based method on the WDM layer for improving resource sharing in grooming process. Extensive simulations are carried out to evaluate the performance of OMP mechanism under different traffic loads, with either limited or unlimited port resources. Simulation results demonstrate that OMP significantly outperforms the existing methods. To evaluate the respective influences of the DL scheme and the LPF method on OMP performance, provisioning mechanisms only utilizing either the IP/MPLS layer DL scheme or the WDM layer LPF method are also devised. Comparison results show that both DL and LPF methods help improve OMP blocking performance, and contribution from the DL scheme is more significant when the fixed routing and first-fit wavelength assignment (RWA) strategy is adopted on the WDM layer. Effects of a few other factors, including definition of connection cost to be reported by the WDM layer to the IP/MPLS layer and WDM-layer routing method, on OMP performance are also evaluated.     

Efficient routing and wavelength assignment for multicast in WDMnetworks

The next generation multimedia applications such as video conferencing and HDTV have raised tremendous challenges on the network design, both in bandwidth and service. As wavelength-division-multiplexing (WDM) networks have emerged as a promising candidate for future networks with large bandwidth, supporting efficient multicast in WDM networks becomes eminent. Different from the IP layer, the cost of multicast at the WDM layer involves not only bandwidth (wavelength) cost, but also wavelength conversion cost and light splitting cost. It is well known that the optimal multicast problem in WDM networks is NP-hard. In this paper, we develop an efficient approximation algorithm consisting of two separate but integrated steps: multicast routing and wavelength assignment. We prove that the problem of optimal wavelength assignment on a multicast tree is not NP-hard; in fact, an optimal wavelength assignment algorithm with complexity of O(NW) is presented. Simulation results have revealed that the optimal wavelength assignment beats greedy algorithms by a large margin in networks using many wavelengths on each link such as dense wavelength-division-multiplexing (DWDM) networks. Our proposed heuristic multicast routing algorithm takes into account both the cost of using wavelength on links and the cost of wavelength conversion. The resulting multicast tree is derived from the optimal lightpaths used for unicast     

QoS aware traffic grooming and integrated routing on IP over WDM networks

In this article, we consider traffic grooming and integrated routing in IP over WDM networks. The challenges of this problem come from jointly considering traffic grooming, IP routing, and lightpath routing and wavelength assignment (RWA). Due to the high bandwidth of optical fiber, there exists a mismatch between the capacity needed by an IP flow and that provided by a single lightpath. Traffic grooming is therefore used to increase the network utilization by aggregating multiple IP flows in a single lightpath. However, traffic grooming incurs additional delays that might violate Quality-of-Service (QoS) requirements of IP users. In this work, the tradeoff between traffic grooming and IP QoS routing is well-formulated as a mixed integer and linear optimization problem, in which the revenue from successfully provisioning IP paths is to be maximized. Problem constraints include IP QoS, routing, optical RWA, and the WDM network capacity. We propose a novel Lagrangean relaxation (LGR) algorithm to perform constraint relaxation and derive a set of subproblems. The Lagrangean multipliers are used in the proposed algorithm to obtain a solution in consideration of grooming advantage and resource constraints simultaneously. Through numerical experiments and comparisons between the proposed algorithm and a two-phase approach, LGR outperforms the two-phase approach under all experimental cases. In particular, the improvement ratio becomes even more significant when the ratio of IP flow to the wavelength capacity is smaller.     

Survivable traffic grooming with non‐service‐interruptive wavelength retuning in a WDM mesh network

This paper proposes a new survivable traffic grooming wavelength retuning (STGWR) scheme in an all‐optical wavelength division multiplexing (WDM) network. In a dynamic WDM network, a connection may require a bandwidth less than a wavelength capacity. In addition, a connection should be protected against any network failures. Survivable traffic grooming (STG) can protect connections at subwavelength granularities. Wavelength retuning is a promising approach in an all‐optical WDM network, where a signal must remain on the same wavelength from its source to the destination, to alleviate the wavelength continuity constraint and reduce the connection blocking probability. Although both STG and wavelength retuning have attracted extensive research attentions nowadays, no effort has been made to combine these two promising approaches in one network. In this paper, we propose a wavelength retuning scheme with no service interruption in an all‐optical network with STG capability. The scheme allocates two routes, one for the active path and other for the backup path, in a shared mesh restoration manner to each incoming connection request and conducts wavelength retuning only on the backup path. Both wavelength retuning and mesh protection are done at the connection level instead of at the lightpath level. The simulation results of the proposed schemes are also presented. Copyright © 2008 John Wiley & Sons, Ltd.