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.     

Capacity planning providing 100 % survivability against double-link failures for WDM Networks

Survivability is always a key concern in WDM optical transport networks as failures may result in large amount of traffic disruption and significant degradation of network performance. In this paper, we investigate the capacity planning problem against double-link failures considering wavelength—continuity constraint. Our objective is to minimize the resource consumption when guaranteeing connection request 100 % survivability. We propose two efficient approaches: (1) the New Static Preplanned Path Protection (NSPPP); (2) the New Dynamic Rerouting (NDR). In NSPPP, we present a new backup resource sharing rule to compress the spare capacity. In NDR, only the working path of connection request is necessary to be given, and the rerouting path can be dynamically found on the network after double-link failures. Compared to previous algorithms, our proposed two capacity planning approaches can efficiently solve double-link failures problem of WDM networks, also obtain higher resource utilization ratio and lower network resource.     

Performance analysis of path rerouting algorithms for handoffcontrol in mobile ATM networks

This paper studies the effects of user mobility and handoff path rerouting on the traffic distributions in a mobile network environment. In mobile ATM networks, extra traffic load may be added to network links due to user mobility and handoff path rerouting. This requires higher network link capacity and possible topology reengineering in order to support the same quality of service (QoS) for mobile services. To capture the dynamic variations in mobile ATM networks, we propose to use a flow model. The model represents the mobile-generated traffic as a set of stochastic flows over a set of origin-destination (OD) pairs. The user mobility is defined by transfer probabilities of the flows and the handoff path rerouting algorithm is modeled by a transformation between the routing functions for traffic flows. The analysis shows that user mobility may cause temporal variations as well as smoothing effects on the network traffic. Using the flow network model, typical handoff path rerouting algorithms are evaluated through both analytical and experimental approaches. The evaluation methodology can be used for either redesigning the network topology for a given path rerouting algorithm or selecting a path rerouting algorithm for a given network topology under a specific mobile service scenario     

基于频谱感知的业务分割-合并的弹性光网络资源分配策略

针对弹性光网络中业务分割的资源分配策略消耗更多保护带与设备端口,浪费频谱资源和增加网络能耗的问题,该文提出一种频谱感知的业务分割再合并的资源分配策略。为新业务分配频谱资源时,先计算路径上总链路剩余频谱连续度,选择使剩余频谱连续度最大频谱块传输业务;当路径上频隙数不满足业务传输需求空闲频谱块时,将该业务分割为多个子业务,尽可能选取使剩余频谱连续度最大的多个频谱块承载各子业务。当监视到子业务传输路径上有可用频隙数满足业务传输所需空闲频谱块时,计算剩余频谱连续度作为子业务合并触发的判决条件,将子业务再合并后继续传输。仿真结果表明该文提出的策略能有效降低网络的带宽阻塞率,并节约网络的能耗。     

Network virtualization over WDM and flexible-grid optical networks

Network virtualization can eradicate the ossification of the Internet and stimulate innovation of new network architectures and applications. Optical networks are ideal substrates for provisioning high-bandwidth virtual-network services. In this study, we investigate the problem of network virtualization over both WDM and flexible-grid optical networks by formulating the problems as mixed integer linear programs (MILP). Two heuristics, namely MaxMapping and MinMapping, are developed for each kind of network to solve the problem quickly but suboptimally. Numerical examples show that MinMapping consumes fewer spectrum resources than MaxMapping and performs very close to the optimal results derived by the MILP in both kinds of optical networks, by exploring the opportunities of traffic grooming. Also, it is verified that flexible-grid optical networks can be more spectrum efficient than WDM networks as the substrate for network virtualization.     

WDM网络中动态流量的资源效率疏导策略

为了解决波分复用(WDM)网状网络中的动态流量疏导问题,基于收发器节约辅助图模型,提出了一种资源效率疏导策略.它同时考虑收发器和波长链路两种网络资源的有效利用,根据当前的网络状态动态改变疏导策略,使网络不会由于某一种资源的缺乏而导致阻塞所有流量,避免了另一种资源因富余而造成的浪费,从而两种资源都能得到充分利用.在辅助图模型中,根据两种资源的可用数目比值,对各条边设置不同的权值函数,可轻易地实现该策略.仿真结果证明,不管是收发器资源受限还是波长资源受限,该策略都能取得较好的性能,降低了网络的阻塞率.     

Resource Planning for Dynamic Traffic Grooming in WDM Optical Networks

Dynamic traffic grooming in wavelength division multiplexing (WDM) optical networks refers to consolidating dynamically arriving subwavelength connections onto lightpaths. Most studies on dynamic traffic grooming focused on designing effective algorithms to achieve better performance (typically blocking probability) with given resources such as wavelengths and transponders. In this paper, we study the reverse problem: given the blocking requirement in dynamic traffic grooming, how to determine the resources needed to meet this requirement. We call it resource planning for dynamic traffic grooming. It is raised in a situation that after the initial deployment of optical networks, service providers often need to upgrade resources to accommodate increasing traffic demands. We formulate it as an ILP problem, and developed heuristics to solve this problem for large networks. Numerical results show that the heuristics can achieve good performance, and network resources increase slowly when requiring lower client call blocking probability.     

Spectrum defragmentation in flexgrid optical networks using a genetic algorithm

Flexgrid optical networking is an attractive solution for efficiently matching allocated bandwidth with link demand but suffers from inevitable spectrum fragmentation. Spectrum fragmentation impairs network performance and results in high blocking rate and low spectrum utilization efficiency. Therefore, an optimization mechanism handling spectrum fragmentation is of vital importance in flexgrid optical networks. In this paper, we propose a genetic algorithm for solving the spectrum fragmentation problem with the objective of compacting occupation of the spectrum in flexgrid optical networks. A string of lightpaths are coded as the chromosome. The spectrum fusion degree and fragment fusion degree are introduced as the fitness functions to conduct the evolution in genetic algorithm, which can also be used to assess the degree of spectrum fragmentation in the network. As a result, the genetic algorithm provides a lightpath reconfiguration map, which identifies the candidate lightpaths to be reallocated, their reconfiguration sequence, and new locations. The proposed algorithm is compared with commonly used approaches under different network conditions. Simulation results demonstrate the ability of the proposed algorithm to efficiently solve the problem of spectrum defragmentation in flexgrid optical networks. Copyright © 2013 John Wiley & Sons, Ltd.     

Session-aware popularity-based resource allocation for assureddifferentiated services

Differentiated services networks are fair in the way that different types of traffic can be associated to different network services, and so to different quality levels. However, fairness among flows sharing the same service, may, not be provided. Our goal is to study fairness between scalable multimedia sessions for assured DS services in a multicast network environment. To achieve this goal, we present a fairness mechanism called session-aware popularity-based resource allocation (SAPRA), which allocates resources to scalable. sessions based on their number of receivers. Simulation results in a scalable and multireceiver scenario show that SAPRA maximizes the utilization, of bandwidth and the number of receivers with high-quality reception     

Resource Allocator for Non Real-Time Traffic in Wireless Networks Using Fuzzy Logic

Providing efficient access to a large user population with variantservice requirements in wireless communications networks poses a verychallenging problem. Resource allocation in the wireless domain shouldtake into account bandwidth limitations and fading effects inherent towireless channels, while accommodating for resource constraintsencountered in wireline networks. In this paper, a fuzzy resourceallocator is proposed in order to facilitate the efficient allocation ofnetwork resources in the wireless domain. The network preferentiallyallocates its resources to real-time (RT) traffic sources. Usingeffective transmission rate statistics of non real-time (NRT) trafficdsources as a measure of fading channel conditions, the fuzzy allocatoroptimally allocates the remaining resources to NRT traffic. Simulationsshow that the fuzzy allocator can reduce delay and incurs fewerretransmissions for NRT traffic. An overall improvement in wirelesschannel utilization is demonstrated.     

WDM网络中静态流量的最少费用疏导策略

为了解决WDM网状网络中的静态流量疏导问题,基于收发器节约辅助图模型,该文提出了一种最少费用疏导策略。它同时考虑收发器和波长链路两种网络资源的费用,为每条流量计算出一条费用最少的路径,以获得网络总费用最少的解决方案。根据两种资源费用的比值关系,给辅助图中的每条边分配不同的权值,使得路径的总权值最小代表了该路径的费用最少,从而就能够轻易地实现该策略。仿真结果证明,不管两种资源的费用比值如何变化,该策略的网络总费用始终是最少的。     

Nodal Architectures for Shared Mesh Restoration of IP and Wavelength Services

Future networks are expected to support heterogeneous traffic, including both Internet Protocol (IP) and wavelength services. IP services are typically restored using IP-layer rerouting mechanisms, whereas wavelength services are restored in the optical layer. With architectures where IP services are mapped into Layer-2 or time-division-multiplexing (TDM) protocols at the network edge, a common restoration mechanism can be utilized for both IP and wavelength services. This letter examines various nodal architectures that can be utilized to support such a unified restoration paradigm.      

Dynamic source aggregation of subwavelength connections in elastic optical networks

Elastic optical network technologies arise as promising solutions for future high-speed optical transmission, since they can provide superior flexibility and scalability in spectrum allocation toward the seamless support of diverse services along with the rapid growth of Internet traffic. In elastic optical networks, heterogeneous traffic demands are typically supported by a single type of bandwidth-variable transmitters, which is not always spectrum and cost-efficient. In light of this, the aggregation of same source but different destination subwavelength connections has been recently introduced for elastic optical networks, aiming to obtain both transmitter and spectrum usage savings. In this paper, we propose a novel algorithm for dynamic source aggregation of connections. Moreover, we introduce a novel node architecture enabling the realization of the proposed source aggregation in a cost-effective way. The obtained results demonstrate considerable improvement in the network spectrum utilization, as well as a significant reduction in the number of necessary transmitters per node.     

An efficient algorithm for virtual-wavelength-path routing minimizing average number of hops

We present a novel heuristic algorithm for routing and wavelength assignment in virtual-wavelength-path (VWP) routed wavelength-division multiplexed optical networks. We are the first to take up the approach of both minimizing the network cost, as well as maximizing the resource utilization. Our algorithm not only minimizes the number of wavelengths required for supporting the given traffic demand on any given topology, but also aims to minimize the mean hop length of all the lightpaths which in turn maximizes the resource utilization. The algorithm initially assigns the minimum hop path to each route and then performs efficient rerouting to reduce the number of wavelengths required while also trying to minimize the average hop length. To further reduce the network cost, we also propose a wavelength assignment procedure for VWP routed networks which minimizes the number of wavelength converters required. Our algorithm has been tested on various topologies for different types of traffic demands and has been found to give solutions much better than previous standards for this problem.     

The designer's perspective to atomic noncooperative networks

In noncooperative networks, resources are shared among selfish users, which optimize their individual performance measure. Traditional design methods tend to perform poorly in such networks, as they do not take into account the inherent noncooperative nature of the network users. Such networks require specialized design techniques in order to achieve efficient utilization of resources. We consider the generic and practically important class of atomic resource sharing networks, in which traffic bifurcation is not implemented, hence each user allocates its whole traffic to one of the network resources. We investigate topologies of parallel resources within a game-theoretic framework and establish the foundations of a design and management methodology that enables operation of such networks efficiently, despite both the lack of cooperation among users and the restrictions imposed by atomic resource sharing. We study various problems pertaining to capacity allocation, pricing, and admission control, and show that their solutions are substantially different from those corresponding to traditional networks     

Dynamic resource management in QoS controlled networks

This paper addresses the problem of resource fragmentation (RF) in QoS controllednetworks. Resources are said to be fragmented when they are available in non-contiguousblocks and hence cannot be utilized by incoming calls with high resource demands. This paper shows the effect of resource fragmentation on QoS controlled networks and presents the Dynamic Resource Redistribution (DRR) algorithm to counteract RF. The DRR algorithm reduces the effects of RF by attempting to redistribute resources in different paths to make resources to incoming calls. A variety of simulation experiments were conducted to study the performance of the DRR algorithm on different network topologies with varying traffic characteristics. The DRR algorithm, when used, increased the number of calls accommodated in the network as well as the overall resource allocation in the network.     

可变带宽光网络中多项式复杂度的频谱扫描路由算法

Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based flexible optical networks, Routing and Spectrum Assignment (RSA) has become a key problem. However, widely used dynamic RSA schemes, such as Fixed Routing (FR) and K-shortest Paths (KSP) routing schemes, are not able to realize route computation based on the link state in-formation, thus leading to poor blocking performance and inefficient resource utilization. To solve this problem, Adaptive Routing (AR) schemes, e.g., the Entire Path Searching (EPS) scheme, have been proposed recently. These schemes have low blocking probability; however, since their computational complexities are factorial, they are not suitable for use in real networks. In this paper, we propose a novel Spectrum-Scan Routing (SSR) scheme in dynamic flexible optical networks. To the best of our knowledge, SSR is the first polynomial-time AR scheme that can realize adaptive shortest-route computation. Simulation results show that our proposed SSR scheme has lower blocking probability and higher resource utilization compared with FR and EPS. Moreover, the worst-case computational complexity of SSR increases linearly with the network scale of the torus topologies, making it applicable to real networks.     

Design of programmable logic device based on electro-optic effect of lithium-niobate-based Mach–Zehnder interferometers

Elastic optical network (EON) technology is considered as a very promising candidate for future high-speed networks due to its intrinsic flexibility and high efficiency in allocating the optical spectrum resources. The key issue that has to be addressed in EON is the routing and spectrum allocation (RSA) problem. RSA is NP-hard problem that has to be solved in an efficient manner. It is a highly challenging task particularly in the case of large problem instances. In this paper, we applied the bee colony optimization (BCO) metaheuristic approach to solve the RSA problem in EON with static traffic demands. The objective of the proposed BCO–RSA algorithm is to minimize both the network spectrum utilization and the average path length criterions. The results of numerous experimental studies show that our BCO–RSA algorithm performs superior compared to some benchmark greedy heuristics as well as to differential evolution (DE) metaheuristic algorithm recently proposed in the literature. The algorithm is evaluated in different realistic size optical networks, such as the NSFnet, two European optical networks (EON-19 and EON-28) and the USA network topology. Simulation results demonstrate that considerable spectrum savings could be achieved with our BCO–RSA algorithm compared to other considered approaches. In addition, we analyzed the efficiency of the BCO–RSA algorithm and compare it with the competitive DE approach according to the required CPU time and the convergence speed.     

Sliding scheduled lightpath provisioning by mixed partition coloring in WDM optical networks

In WDM optical networks, lightpath provisioning for static, incremental and dynamic traffic model has been widely investigated. However, Internet connectivity services are increasingly showing a new kind of traffic type in the context of optical networks, i.e., sliding scheduled traffic, which does not have a rigid deadline and allows flexible sliding within a large time window. This new traffic type offers opportunity of more efficiently utilizing network resources to accommodate more traffic, and poses new challenges of exploiting the flexibility of scheduling time. In this paper, we formulate the static sliding scheduled lightpath demand (SSLD) provisioning problem as a mixed partition coloring model in which routing and wavelength assignment are conducted simultaneously in compliance with the allowed time window of each request. Then, we propose a novel one-step heuristic algorithm named as maximum conflict degree first conflict reducing (MCDF-CR) to solve the SSLD provisioning problem based on mixed partition coloring model. Simulation results show that our approach can improve wavelengths utilization compared to previous heuristics.     

Survivable MPLS Over Optical Transport Networks: Cost and Resource Usage Analysis

In this paper we study different options for the survivability implementation in MPLS over optical transport networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the offered traffic granularity and the physical network structure on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. On the other hand, sparse networks of low connectivity parameter use more wavelengths for optical path routing and increase the configuration cost, as compared with dense networks. We demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with different cost variations, and were obtained for networks targeted to a nationwide coverage