Achieving Resource-Efficient Survivable Provisioning in Service Differentiated WDM Mesh Networks

A resource-efficient provisioning framework (RPF) is proposed in this paper for optical networks providing dedicated path protection (DPP) and shared path protection (SPP) services. The framework reduces resource consumption by considering spare capacity reservation of DPP and SPP cooperatively while provides 100% survivability guarantee and maintains the recovery time for both protection types against the predominant single link failures. To tackle the service provisioning problem under the framework, an integer linear programming (ILP) formulation is presented to find the optimal routing solution for a given set of traffic demands. The objective is to minimize total capacities consumed by working and backup paths of all demands. Then, heuristics are developed for on-line routing under dynamic change of traffic. Numerical results show that compared with traditional provisioning framework (TPF), the RPF has the following advantages: 1) Over 10% capacity savings are achieved for static service provisioning; 2) blocking probability of both protection types is greatly reduced; 3) lower resource overbuild is achieved; and 4) average backup-path hop distance of shared-path-protected flows is reduced. Finally, network survivability in face of double link failures is discussed under the framework.      

WDM网络动态组播业务共享保护算法

该文研究了WDM网络中动态组播业务的保护.为提高网络资源的利用率,降低连接请求阻塞率,和单播业务的共享保护方案类似,组播连接之间也可以共享保护波长.本文提出了一种动态组播业务共享保护算法,并对算法的性能进行了仿真,同时和组播业务专有保护算法进行了比较.仿真结果表明,共享保护算法比专有保护算法使用了更少的波长资源,具有更低的连接阻塞率.     

WDM网状网中支持业务量疏导的区分共享保护算法

该文综合考虑WDM网状网生存性及业务量疏导,采用部分光路共享保护机制为低速业务提供满足其可靠性和带宽需求的连接,提出了一种基于波长分层图的支持业务量疏导的区分共享保护算法—部分共享保护业务量疏导算法PSPTG(PartialShared-pathProtectionalgorithmsupportingTrafficGrooming)。仿真结果表明:该算法可以较好地利用资源。     

Routing Connections With Differentiated Reliability Requirements in WDM Mesh Networks

Reliability has been well recognized as an important design objective in the design of modern high-speed networks. While traditional approaches offer either 100% protection in the presence of single link failure or no protection at all, connections in real networks may have multiple reliability requirements. The concept of differentiated reliability (DiR) has been introduced in the literature to provide multiple reliability requirements in protection schemes that provision spare resources.      

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。     

Quality-of-Service Based Protection in MPLS Control WDM Mesh Networks

Intelligent methods for automatic protection and restoration are critical in optical transport mesh networks. This paper discusses the problem of quality-of-service (QoS)-based protection in terms of the protection-switching time and availability for end-to-end lightpaths in a WDM mesh network. We analyze the backup lightpath-sharing problem in such networks and study the correlation of the working lightpaths and the impact of the correlation on the sharing of the backup lightpaths. We present a multi-protocol-label-switching (MPLS) control-based fully distributed algorithm to solve the protection problem. The proposed algorithm includes intelligent and automatic procedures to set up, take down, activate, restore, and manage backup lightpaths. It greatly reduces the required resources for protection by allowing the sharing of network resources by multiple backup lightpaths. At the same time, it guarantees, if possible, to satisfy the availability requirement even with resource sharing by taking the correlation of working lightpaths into consideration. A simple analysis of the proposed algorithm in terms of computation time and message complexity indicates that the implementation of the algorithm is practical. The illustrative studies that compare the performance of 1:1, unlimited sharing, and QoS-based backup sharing algorithms indicate that QoS-based sharing achieves comparable performance as unlimited sharing, which is much better than the 1:1 backup scheme in terms of connection blocking probability, average number of connections in the network for a given offered load, and network resource utilization.     

Shared Sub-Path Protection Algorithm in Traffic-Grooming WDM Mesh Networks

In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.     

网状WDM网中支持区分可靠性的共享通路保护算法

光纤链路由于共享了某些物理资源(如光缆、管道、通路等),因此存在一定的故障相关性,术语“共享风险链路组(SRLG)”就是用于描述链路之间的这种风险共享关系的。SRLG分离成为保护设计的重要约束。该文研究了支持区分可靠性的SRLG分离共享通路保护设计问题。结合SRLG条件故障概率的概念,提出了部分SRLG分离的共享保护算法PSD-SPP(PartialSRLG-DisjointShared-PathProtection),有效地解决了SRLG分离约束下的区分可靠性设计问题。仿真结果表明该算法既满足了用户的区分可靠要求,又能有效利用资源。     

Reliable Multipath Provisioning for High-Capacity Backbone Mesh Networks

We investigate reliable multipath provisioning of traffic in high-capacity backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that may lead to significantly improved performance over conventional single-path provisioning. Other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multiprotocol label switching (MPLS) can also benefit from this multipath provisioning approach. We propose effective multipath bandwidth as the metric to provision a connection while satisfying its reliability requirements (measured in terms of availability). We demonstrate that effective multipath bandwidth provides more flexibility and lower blocking probability without the cost and the complexity associated with traditional protection schemes developed for optical WDM and MPLS networks. We also investigate the practical problem of provisioning effective multipath bandwidth with cost constraints. We analyze the tractability of the problem and present a heuristic which results in significantly reduced number of blocked connections due to cost constraints.     

Service-Centric Provisioning in WDM Backbone Networks for the Future Internet

A service level agreement (SLA) is a formal contract between the service provider (SP) and the customer. Among various specifications, the SLA states an availability requirement and a penalty the SP pays if this requirement is violated. Traditional approaches to protection use a fixed deployment of backup resources, or do not consider the status of a service. As more heterogeneous applications use optical wavelength-division multiplexing (WDM) backbone network services of the future internet, these service-agnostic approaches are unable to accommodate the differentiated availability requirements. This results in substantial revenue loss either by refusing requests, or by accepting them and then violating their SLAs. In this paper, we propose and investigate the characteristics of a centralized control and management framework for service-aware, admission, and re-provisioning (SAR) in WDM backbone networks of the future internet. Our framework aggressively admits service requests, and dynamically reprovisions existing services by exploiting knowledge of their status. We first propose a GMPLS-based architecture and a revenue model for our analysis. Then we introduce a priority index, called urgency level (UL). An UL is assigned to an existing service indicating its status and relative importance, technically and economically. We reprovision resources by shifting them from low-UL services to provide backups for higher-UL services, which are more at risk of violating their SLAs or which have higher penalties. Our framework increases the revenue for the SP by creating more sales revenue and reducing potential penalties. Numerical results show improved performance in terms of 1) lower resource overbuild; 2) lower bandwidth blocking ratio; 3) higher SLA satisfaction ratio; 4) more balanced SLA violations; and 5) higher overall net revenue. Our framework is also shown to be effective for a range of failure models and penalty strategies.      

Light-Path Provisioning of the WDM Optical Networks

1IntroductionThere is no doubt that, in the predictable near fu-ture, the circuit switching paradigm will continuously play an active role in the commercial wavelength-divi-sionmultiplexing (WDM) optical networks. In such envi-ronments the end-to-end services are provided by light-paths(LPs) which are established prior to the ses-sion of data transmissions. Like its electronic counter-part, the WDM network is a multi-layer architecture. On the physical layer, the WDM network can be chara…     

A Novel Shared Segment Protection Algorithm for Multicast Sessions in Mesh WDM Networks

This paper investigates the problem of protecting multicast sessions in mesh wavelength‐division multiplexing (WDM) networks against single link failures, for example, a fiber cut in optical networks. First, we study the two characteristics of multicast sessions in mesh WDM networks with sparse light splitter configuration. Traditionally, a multicast tree does not contain any circles, and the first characteristic is that a multicast tree has better performance if it contains some circles. Note that a multicast tree has several branches. If a path is added between the leave nodes on different branches, the segment between them on the multicast tree is protected. Based the two characteristics, the survivable multicast sessions routing problem is formulated into an Integer Linear Programming (ILP). Then, a heuristic algorithm, named the adaptive shared segment protection (ASSP) algorithm, is proposed for multicast sessions. The ASSP algorithm need not previously identify the segments for a multicast tree. The segments are determined during the algorithm process. Comparisons are made between the ASSP and two other reported schemes, link disjoint trees (LDT) and shared disjoint paths (SDP), in terms of blocking probability and resource cost on CERNET and USNET topologies. Simulations show that the ASSP algorithm has better performance than other existing schemes.     

无线Mesh网络QoS保障技术综述

首先,简要回顾了无线Mesh网络的基本概况,分析了在无线Mesh网络中提供QoS保障的必要性和重要意义。然后,系统地介绍了无线Mesh网络的物理层、MAC层和路由层QoS保障技术以及跨层QoS设计技术的国内外研究现状,对其进行了细致而科学的分类。最后,给出了它们的研究难点和研究方向。     

Connection Management Protocols for Dynamic Lightpath Provisioning in Future WDM Networks

This paper investigates and compares the performance of two GMPLS-based distributed control and management protocols for dynamic lightpath provisioning in future IP networks. The first protocol is a global information-based link state approach that consists of both an integrated RWA algorithm and a signaling algorithm. Two triggering mechanisms for the LSAs update procedures are considered; one is periodic-based and the other is threshold-based. The second protocol is a local-information based fixed alternate link routing approach where the signaling protocol is closely integrated with the RWA protocols.     

Provisioning Methods for Bit-Rate-Differentiated Services in Hybrid Optical Networks

This paper addresses the problem of routing and wavelength assignment of bit-rate-differentiated optical services in a hybrid network. Hybrid optical networks are composed of resources, such as fiber links and photonic/electronic switches, that vary in their capabilities and transmission qualities. These networks are also responsible for the realization of optical services with varying quality-of-service (QoS) guarantees. In such networks, it is required to have a cost-effective assignment of the optical and electronic resources to these services in order to maximize the revenue of the network operator. This paper deals with optical services that are defined according to their tolerance to transmission impairments. We first divide the provisioning problem into two phases: (1) routing and (2) wavelength assignment and regeneration reservation. In the routing phase, a set of k-routes are generated to select from in the second phase, where each route optimizes a specific aspect of the problem (e.g., number of hops, maximum accumulated noise, etc.). The second phase, using the information about the resources along each route, attempts at finding the best wavelength allocation on that route such that the signal quality meets the service-level agreement (SLA). The second phase also uses the minimum number of regenerator ports on intermediate nodes for the purpose of wavelength translation and signal clean-up. Comparisons of the above scheme with a probing-based method, reveal substantial enhancements to the blocking performance with a maximum running time increase of 60%. In addition, the use of multiple routes provides higher reduction in the blocking probability over single-routing schemes. Moreover, the proposed, non-pessimistic, provisioning approach has a major impact on reducing the regeneration budget of the network.     

WDM网状网中鲁棒选路算法研究

研究了WDM网状网在hose业务模型下基于Valiant负载平衡的鲁棒选路问题。借助业务量疏导的方法,以hose模型吞吐量最大化为优化目标,采用整数线性规划（ILP）加以解决,进而提出了2种快速的启发式算法——最短路径选路的最小跳数优先（SPR＆MHF）算法和平衡选路的最小跳数优先（BR＆MHF）算法。计算机仿真表明,SPR＆MHF算法适用于链路数较少的小规模WPM网状网,而RR＆MHF适用于链路数较多的大规模WDM网状网。     

QoS Provisioning in Wireless Mesh Networks: A Survey

Wireless Personal Communications - With the recent developments in Wireless Mesh Networks (WMN), provisioning of Quality of Service (QoS) for real time applications is considered as an important...     

Dynamic Grooming Algorithms for Survivable WDM Mesh Networks

Within a WDM grooming mesh network and under the constraints of the number of transceivers per node and wavelength continuity, we propose a novel dynamic grooming graph which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources. Based on the grooming graph, we first propose a dynamic traffic-grooming algorithm called integrated grooming algorithm (IGA). And we also propose two dynamic survivable traffic-grooming algorithms, which are called protection per lightpath traffic-grooming algorithm (PPL) and protection per connection traffic-grooming algorithm (PPC). These algorithms are evaluated via simulations.     

Cost Effective Shared Path Protection for WDM Optical Mesh Networks with Partial Wavelength Conversion

In this paper, we study routing and wavelength assignment of connection requests in survivable WDM optical mesh networks employing shared path protection with partial wavelength conversion while 100% restorability is guaranteed against any single failures. We formulate the problem as a linear integer program under a static traffic model. The objective is to minimize the total cost of wavelength-links and wavelength converters used by working paths and protection paths of all connections. A weight factor is used which is defined as the cost ratio of a wavelength converter and a wavelength-link. Depending on the relative cost of bandwidth and wavelength conversion, the optimization objective allows a proper tradeoff between the two. The proposed algorithm, the shortest-widest-path-first (SWPF) algorithm, uses a modified Dijkstra's algorithm to find a working path and a protection path for each connection request in the wavelength graph transformed from the original network topology. When there are multiple candidate paths that have the same minimum total cost, the path along which the maximum number of converters used at each node is minimized is chosen by the SWPF algorithm. We have evaluated the effectiveness of the proposed algorithm via extensive simulation. The results indicate that the performance of the proposed algorithm is very close to that of the optimal solutions obtained by solving the ILP formulation and outperforms existing heuristic algorithms in terms of total number of converters used and the maximum number of converters required at each node in the network. The proposed algorithm also achieves slightly better performance in terms of total cost of wavelength-links and converters used by all connections. We also investigated shared path protection employing converter sharing. The results show that the technique can reduce not only the total number of converters used in the network but also the maximum number of converters required at each node, especially when a large number of converters are needed in the network. In this study, although the ILP formulation is based on static traffic, the proposed algorithm is also applicable to routing dynamic connection requests.     

Dynamic Establishment of Segmented Protection Paths in Single and Multi-Fiber WDM Mesh Networks

Wavelength division multiplexed (WDM) networks are matured to provide, scalable data centric infrastructure, capable of delivering flexible, value added, high speed and high bandwidth services directly from the optical (WDM) layer. But, providing fault-tolerance at an acceptable level of overhead in these networks has become a critical problem. This is due to the size of the current and future networks and diverse quality of service (QoS) requirements for multimedia and mission critical applications. Several distributed real-time applications require communication services with fault-tolerance apart from guaranteed timeliness at acceptable levels of overhead. Several methods exist in the literature which attempt to guarantee recovery in a timely and resource efficient manner. These methods are centered around a priori reservation of network resources called spare resources along a protection path. This protection path is usually routed from source to destination along a totally link disjoint path from primary path. This paper considers the problem of routing and wavelength assignment (RWA) in wavelength routed WDM optical networks. In particular, we propose an efficient algorithm to select routes and wavelengths to establish dependable connections (D-connections), called segmented protection paths. Our algorithm does not insist on the existence of totally disjoint paths to provide full protection. We present experimental results which suggest that our scheme is attractive enough in terms of average call acceptance ratio, spare wavelength utilization, and number of requests that can be satisfied for a given number of wavelengths assuming that the requests come one at time, and wavelengths are assigned according to fixed ordering. Furthermore, the results suggest that our scheme is practically applicable for medium and large sized networks, which improves number of requests that can be satisfied and helps in providing better QoS guarantees such as bounded failure recovery time and propagation delays without any compromise on the level of fault-tolerance for a given number of wavelengths and fibers. We conduct extensive simulation experiments to evaluate the effectiveness of the proposed scheme on different networks and compare with existing methods.This work was supported by the Department of Science and Technology, New Delhi, India. An earlier version of this paper was presented at Opticomm 2002 conference, July 29-August 2, Boston, USA.