Availability-Aware Provisioning Strategies for Differentiated Protection Services in Wavelength-Convertible WDM Mesh Networks

In an optical WDM mesh network, different protection schemes (such as dedicated or shared protection) can be used to improve the service availability against network failures. However, in order to satisfy a connections service-availability requirement in a cost-effective and resource-efficient manner, we need a systematic mechanism to select a proper protection scheme for each connection request while provisioning the connection. In this paper, we propose to use connection availability as a metric to provide differentiated protection services in a wavelength-convertible WDM mesh network. We develop a mathematical model to analyze the availabilities of connections with different protection modes (i.e., unprotected, dedicated protected, or shared protected). In the shared-protection case, we investigate how a connection's availability is affected by backup resource sharing. The sharing might cause backup resource contention between several connections when multiple simultaneous (or overlapping) failures occur in the network. Using a continuous-time Markov model, we derive the conditional probability for a connection to acquire backup resources in the presence of backup resource contention. Through this model, we show how the availability of a shared-protected connection can be quantitatively computed. Based on the analytical model, we develop provisioning strategies for a given set of connection demands in which an appropriate, possibly different, level of protection is provided to each connection according to its predefined availability requirement, e.g., 0.999, 0.997. We propose integer linear programming (ILP) and heuristic approaches to provision the connections cost effectively while satisfying the connections' availability requirements. The effectiveness of our provisioning approaches is demonstrated through numerical examples. The proposed provisioning strategies inherently facilitate the service differentiation in optical WDM mesh networks.     

Upgrading service availability of optical networks: A labor force perspective

Service availability is an important issue in optical networks. Much research attention has been drawn to the provisioning of reliable connections achieved by approaches such as routing and wavelength assignment and by protection and restoration mechanisms. In contrast, the research on upgrading networks to meet new or dynamic demands of service availability based on network upgrading process has been comparatively lacking. In this paper, we address this issue by upgrading service availability from the perspective of labor forces for network maintenance. Our approach is premised on the assumption that the time period for fixing an optical link can be reduced by using more network resources of labor forces. To model this concept, we conduct Amdahl's law, a well‐known theorem in parallel computing, to describe human teamwork. To show the effectiveness of this concept, we propose mixed integer linear programming aiming at either maximizing service availability under limited labor forces or minimizing labor forces for predetermined service availability. In addition, a heuristic algorithm for upgrading service availability is presented. Our experimental results show that our network upgrading process can improve service availability optimally with a fixed number of forces and the proposed heuristic algorithm can effectively save computation time.     

Availability-aware service provisioning in SD-EON-based inter-datacenter networks

The tremendous transmission capacity and flexible spectrum allocation scheme make elastic optical networks (EONs) one of the most promising infrastructures for constructing the interconnection in datacenter (DC) networks. Meanwhile, as DC traffics exhibit highly dynamic and heterogeneous features, differentiated service provisioning schemes are desired. In this paper, we take the advantage of centralized network control and management provided by the software-defined elastic optical networks (SD-EONs) and investigate availability-aware service provisioning in SD-EON-based inter-datacenter (inter-DC) networks. We first describe the problem of availability-aware service provisioning in SD-EON-based inter-DC networks and present the theoretical analysis for service availability. Then, we propose an availability-aware service provisioning algorithm (ASP) that leverages different path protection schemes to satisfy different service availability requirements. A service downgrading (SD) strategy is also designed as a supplement of ASP to further improve its performance. Simulation results show that the proposed ASP-SD algorithm can effectively improve the spectrum efficiency without sacrificing availability.     

A review of fault management in WDM mesh networks: basic concepts and research challenges

The article first presents a broad overview of the fault management mechanisms involved in deploying a survivable optical mesh network which employs optical crossconnects. We review various protection and restoration schemes, primary and back-up route computation methods, shareability optimization, and dynamic restoration. We then describe different parameters that can measure the quality of service provided by a WDM mesh network to upper protocol layers (e.g., IP network backbones, ATM network backbones, leased lines, virtual private networks), such as service availability, service reliability, restoration time, and service restorability. We review these concepts, the factors that affect them, and how to improve them. In particular, we present a framework for cost-effective availability-aware connection provisioning to provide differentiated services in WDM mesh networks. Through the framework, the more realistic scenario of multiple near-simultaneous failures can be handled. In addition, the emerging problem of protecting low-speed connections of different bandwidth granularities is also reviewed.     

Joint wireless and optical resources allocation for availability-guaranteed service in survivable fiber-wireless access network

The fiber-wireless (FIWi) access network not only leverages the technical merits of wireless and optical access networks, but also provides a potential opportunity for the design of survivable access networks. Previous works have studied the survivability of FiWi access network against network component failure by means of backup fiber deployment and wireless rerouting. However, most of these works put less attention on the connection availability and ignore the joint allocation of wireless and optical resources, which plays an important role in improving the global network performance gain. In this paper, we consider a notable failure scenario in FiWi access network but less mentioned in previous works, i.e., single shared-risk link group failure. We first propose a model for FiWi network to estimate the connection availability of service demand. Then, a novel resource allocation approach is proposed to provide the availability-guaranteed service. Under the requirements of bandwidth and connection availability, we deal with the optimal allocation of joint wireless and optical resources with the objective of minimum resource consumption. Numerical results demonstrate that the proposed scheme can reduce the resource consumption significantly compared to the resource allocation without considering connection availability.     

新一代智能城域光网络

本文介绍了一种标准化的光控制平面。光控制平面被分解成邻居发现、服务发现、连接控制和拓扑/资源发现等几个基本的过程。不同的网络组织和分割导致了几个不同的自动配置模型：软性持久链路模型、用户接口模型和对等模型。最后还介绍了基于SDH光交换的新一代CIENA公司智能光网络，它具有大容量光交换能力和网络拓扑结构自动发现、端对端电路配置、带宽动态分配等功能及特点，将大大提高数据、电路业务的服务质量。     

A multilayer solution for path provisioning in new-generation optical/MPLS networks

This paper proposes an offline solution for global path provisioning in new-generation optical networks based on the generalized multiprotocol label switching (GMPLS) paradigm. This solution is based on a multilayer approach, which involves both the optical and the electrical layers and optimizes the network configuration and traffic routing. The proposed global provisioning solution can be easily combined with dynamic routing solutions, providing the network with the possibility of reacting promptly to traffic changes. Data flows are assumed to be structured into label switched paths (LSPs), which represent the connection in a GMPLS-based network, at any hierarchical level. The global provisioning issue is a difficult optimization problem. As a solution, we propose a new heuristic algorithm based on the shortest path computation and a mathematical programming approach, which makes use of the optimization solver CPLEX. A large computational study shows the effectiveness of the former, in terms of quality of the solutions. The advantages of the multilayer provisioning strategy are analyzed in a relevant case study by evaluating the network congestion.     

Shared Risk Link Group (SRLG)-Diverse Path Provisioning Under Hybrid Service Level Agreements in Wavelength-Routed Optical Mesh Networks

The static provisioning problem in wavelength-routed optical networks has been studied for many years. However, service providers are still facing the challenges arising from the special requirements for provisioning services at the optical layer. In this paper, we incorporate some realistic constraints into the static provisioning problem, and formulate it under different network resource availability conditions. We consider three classes of shared risk link group (SRLG)-diverse path protection schemes: dedicated, shared, and unprotected. We associate with each connection request a lightpath length constraint and a revenue value. When the network resources are not sufficient to accommodate all the connection requests, the static provisioning problem is formulated as a revenue maximization problem, whose objective is maximizing the total revenue value. When the network has sufficient resources, the problem becomes a capacity minimization problem with the objective of minimizing the number of used wavelength-links. We provide integer linear programming (ILP) formulations for these problems. Because solving these ILP problems is extremely time consuming, we propose a tabu search heuristic to solve these problems within a reasonable amount of time. We also develop a rerouting optimization heuristic, which is based on previous work. Experimental results are presented to compare the solutions obtained by the tabu search heuristic and the rerouting optimization heuristic. For both problems, the tabu search heuristic outperforms the rerouting optimization heuristic.     

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.      

新一代智能城域光网络

本提出了一种标准化的光控制平面。阐明了开了用于光传输网的控制平面所遇到的选择与挑战。光控制平面被分解成邻居发现、服务发现、连接控制和拓扑、资源发现等几个基本的过程。不同的网络组织和分割导致了几个不同的自动配置模型：软性持久链路模型、用户接口模型和对等模型。这是构成以IP为中心的光传输网的控制和管理基础。同时也介绍了基于SDH光交换的新一代CIENA公司智能光网络，它具有大容量光交换能力和网络拓扑结构自动发现、端对端电路配置、带宽动态分配等功能及特点，将大大提高数据、电路业务的服务质量，新一代智能光网络是干线和城域网络交换传输最佳的选择。     

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.     

WDM optical network testbed and distributed storage application

In this article we present the details of a generalized multiprotocol label switching controlled wavelength-division multiplexing (WDM) optical network developed under the Optical Network Focused Interest Group (ONFIG) program in Singapore. The WDM network is controlled through a GMPLS control plane that consists of CR-LDP, LMP, and OSPF-TE. We conducted various field trials on the GMPLS-capable WDM optical network testbed with the main focus on distributed storage service application. We developed and evaluated a distributed storage services application on the WDM optical network testbed and demonstrated that incorporating a lightweight data transport protocol with optical network control could be an efficient approach for data-intensive storage applications by exploiting the dynamic connection establishment and backup protection features.     

RETRACTED ARTICLE: Research on Energy Saving Design of Intelligent Building Based on Genetic Algorithm

Generalized Multiprotocol Label Switching (GMPLS) networks is capable of allocating suitable route based on the size of the network and computational constraints. In this paper, we propose a connection provisioning strategy for updating the Traffic Engineering Database of Path Computation Element (PCE) in GMPLS optical networks. Control and management plane are used for resource optimization in PCE-based centralized network. We have also proposed connection provisioning for Label Switched Path (LSP) to optimize the resources and to maximize the connection establishment. For provisioning a connection with LSP requests, we have formulated the Integer Linear Programming and constraints to minimize the blocking of connections and network performance. The results obtained shows that the proposed strategy has better network resource utilization with minimum blocking of connections.     

Availability analysis under multiple link failures in WDM networks with shared-link connections

In optical Wavelength Division Multiplexing (WDM) networks, different protection schemes have been proposed in the literature, namely, dedicated protection and shared protection. Shared protection techniques significantly reduce the required spare capacity by providing the same level of availability as dedicated protection. However, current mission critical applications (which heavily depend on the availability of communication resources) require connection availability in the order of 99.999% or higher, which corresponds to a downtime of almost 5 min a year on the average. Therefore, in order to satisfy a connection serviceavailability requirement defined by the users Service Level Agreement in a cost-effective and resource-efficient way, network operators need a systematic mechanism to evaluate the network availability under multiple failure scenario to ensure that current network configuration can meet the required availability degree; otherwise, a network upgrade is required. Unfortunately, under multiple failure scenario, traditional availability analysis techniques based on reliability block diagrams are not suitable for survivable networks with shared spare capacity. Therefore, a new concept is proposed to facilitate the calculations of network availability. In this paper, we propose an analytical model for evaluating the availability of a WDM network with shared-link connections under multiple link failures. The analytical model is also verified using Monte Carlo simulation. The proposed model significantly contributes to the related areas by providing network operators with a quantitative tool to evaluate the system availability and, thus, the expected survivability degree of WDM optical networks with shared connections under multiple link failures.     

光网络接口信令系统容错设计的分析和验证

为实现动态指配光网络资源功能，提出了一种用户网络接口（UNI）信令协议系统，该协议系统基于层叠模型，支持多种类客户寻址，分析了协议系统设计的出错处理并采用时序逻辑描述和验证了其容错性质，验证结果表明，系统在网络正常和超时故障条件下均能确保对光通道的建立，修改、拆除和查询等操作无误。     

Robust QoS Control for Single Carrier PMP Mode IEEE 802.16 Systems

The IEEE 802.16 WirelessMAN standard provides a comprehensive quality-of-service (QoS) control structure to enable flow isolation and service differentiation over the common wireless network interface. By specifying a particular set of service parameters, the media access control (MAC) mechanisms defined in the standard are able to offer predefined QoS provisioning on a per-connection basis. However, the design of efficient, flexible, and yet robust MAC scheduling algorithms for such QoS provisioning still remains an open topic. This paper proposes a new QoS control scheme for single-carrier point-to-multipoint mode wireless metropolitan area network (WirelessMAN) systems, which enables the predefined service parameters to control the service provided to each uplink and downlink connection. By MAC-PHY cross-layer resource allocation, the proposed scheme is robust against particular wireless link degradation. Detailed simulation experiments are presented to study the performance and to validate the effectiveness of the proposed QoS control scheme.     

High availability path design in ring-based optical networks

This work develops mathematical models for path availability and provisioning resources required in various strategies for realizing high availability service paths in a transport environment of bidirectional line-switched rings or shared protection optical (wavelength division multiplexing) rings. The work originated in response to user requests for SONET service paths with unavailabilities under 30 s/year. A number of schemes for redundant routing and ring interconnection are considered as options to meet such a demanding target in the most economic way. An analytical framework for comparison of various provisioning schemes allows a “cost effectiveness” assessment of four high-performance alternatives, in terms of total resource investment and the corresponding service unavailability relative to a single-fed path construction. The logical models of cost and availability can be used in a variety of SONET or optical-ring transport planning studies or perhaps in future automated provisioning tools. An important finding is that while the availability benefit of dual-ring interconnection is high in metro-ring networks, the availability of paths through long-haul ring networks may be relatively poor due to lower limits from two-failure intra-ring combinations     

一种新的动态指配光网络资源的接口信令协议

本文提出了一种新的用户光网络接口(UNI)信令协议,以实现动态指配光网络资源的功能.该协议支持多种类客户寻址,考虑了光网络的特殊要求.采用通信有限状态机(CFSM)模型对协议进行了形式化描述和验证,分析了协议设计的出错处理.分析和验证结果表明,协议在网络正常和超时故障条件下均能确保对光通道的建立、修改、拆除和查询等操作无误,具有无死锁、无活锁、完整性和容错性等重要性质.     

A flexible and distributed architecture for adaptive end-to-end QoS provisioning in next-generation networks

A novel distributed end-to-end quality-of-service (QoS) provisioning architecture based on the concept of decoupling the end-to-end QoS provisioning from the service provisioning at routers in the differentiated service (DiffServ) network is proposed. The main objective of this architecture is to enhance the QoS granularity and flexibility offered in the DiffServ network model and improve both the network resource utilization and user benefits. The proposed architecture consists of a new endpoint admission control referred to as explicit endpoint admission control at the user side, the service vector which allows a data flow to choose different services at different routers along its data path, and a packet marking architecture and algorithm at the router side. The achievable performance of the proposed approach is studied, and the corresponding results demonstrate that the proposed mechanism can have better service differentiation capability and lower request dropping probability than the integrated service over DiffServ schemes. Furthermore, it is shown that it preserves a friendly networking environment for conventional transmission control protocol flows and maintains the simplicity feature of the DiffServ network model.     

Performance Analysis of Infrastructure Service Provision with GMPLS-Based Traffic Engineering

Dynamic sharing of the common physical network is envisioned as a key enabler for the emerging Internet technologies. This paper addresses challenges related to resource sharing in the physical layer and analyzes the performance of infrastructure service provision with control plane mechanisms based on generalized multi protocol label switching (GMPLS). In our approach, the provisioning of infrastructure services is supported by two novel concepts for GMPLS traffic engineering (TE): resource visibility and inter-domain exchange. Resource visibility is a new network control plane concept, which defines the usage polices for transmission, multiplexing, and switching resources in multiple GMPLS layers. In our architecture, every network resource may exhibit different visibility to different services at different layers. The inter-domain exchange, here referred to as GMPLS exchange point (GXP), is the physical layer equivalent of the Internet exchange point (IXP). Just as how the IXP manages interconnections of autonomous systems (AS) in the Internet, the GXP manages dynamic interconnections of multiple provider domains and enables them to advertise their physical resources to other domains. We model the dynamic provisioning of infrastructure services using graph theory and deploy GMPLS traffic engineering (TE) to optimize the routing and resource yields. The results obtained demonstrate that traffic engineering with resource visibility and GXP brings significant performance benefits in resource utilization and infrastructure extensibility, especially when network providers set up LSPs as a result of collaborative and carrier-neutral traffic engineering where they share information about resource capabilities and utilization