Resource provisioning for survivable WDM networks under a sliding scheduled traffic model

Resource allocation in WDM networks, under both the static and dynamic traffic models have been widely investigated. However, in recent years there has been a growing number of applications with periodic bandwidth demands. Resources for such applications can be scheduled in advance, leading to a more efficient utilization of available network capacity. The setup and teardown times of the scheduled demands may be fixed, or may be allowed to slide within a larger window. A number of optimal integer linear program (ILP) solutions for the first problem (fixed setup/teardown times) have been presented in the literature. In this paper we present two new ILP formulations for the more general sliding scheduled traffic model, where the setup and teardown times may vary within a specified range. We first consider wavelength convertible networks and then extend our model to networks without wavelength conversion. Our ILP formulations jointly optimize the problem of scheduling the demands (in time) and allocating resources for the scheduled lightpaths. The fixed window model can be treated as a special case of our formulations. Our formulations are able to generate optimal solutions for practical sized networks. For larger networks, we have proposed a fast two-step optimization process. The first step schedules the demands optimally in time, so that the amount of overlap is minimized. The second step uses a connection holding time aware heuristic to perform routing and wavelength assignment for the scheduled demands.     

Physical layer performance benchmarking of two metropolitan area network configurations

This paper investigates the problem of dynamic survivable lightpath provisioning against single-node/link failures in optical mesh networks employing wavelength-division multiplexing (WDM).We unify various forms of segment protection into generalized segment protection (GSP). In GSP, the working path of a lightpath is divided into multiple overlapping working segments, each of which is protected by a node-/link-disjoint backup segment. We design an efficient heuristic which, upon the arrival of a lightpath request, dynamically divides a judiciously selected working path into multiple overlapping working segments and computes a backup segment for each working segment while accommodating backup sharing. Compared to the widely considered shared-path protection scheme, GSP achieves much lower blocking probability and shorter protection-switching time for a small sacrifice in control and management overhead.On the basis of generalized segment protection, we present a new approach to provisioning lightpath requests according to their differentiated quality-of-protection (QoP) requirements. We focus on one of the most important QoP parameters—namely, protection-switching time—since lightpath requests may have differentiated protection-switching-time requirements. For example, lightpaths carrying voice traffic may require 50 ms protection-switching time while lightpaths carrying data traffic may have a wide range of protection-switching-time requirements. Numerical results show that our approach achieves significant performance gain which leads to a remarkable reduction in blocking probability.While our focus is on the optical WDM network, the basic ideas of our approaches can be applied to multi-protocol label switching (MPLS) networks with appropriate adjustments, e.g., differentiated bandwidth granularities.     

Optical networking and real-time provisioning: an integrated visionfor the next-generation Internet

This article considers the problem of real-time provisioning of optical channels in hybrid IP-centric DWDM-based networks. First, we present an overview of the emerging architectural alternatives for IP over optical networks, namely, the overlay, the peer, and the augmented models. Then lightpath provisioning issues are detailed for route selection, with a particular focus on the “routing and wavelength assignment” (RWA) problem. In particular, a broad overview is presented, with methodologies and associated algorithms for dynamic lightpath computation being outlined. Additionally, two broad constraint-based RWA algorithms for dynamic provisioning of the optical channels are presented and evaluated. Finally, the implications of implementing the proposed RWA schemes for the lightpath provisioning aspects for each of the three emerging IP over optical network interconnection models are examined     

A Hybrid RF and Vision Aware Fusion Scheme for Multi-Sensor Wireless Capsule Endoscopic Localization

A huge torrent of data traffic is generated from various heterogeneous applications and services at the Internet backbone. In general, at the backbone, all such applications and services are allocated spectral resources under a shared spectrum environment within elastic optical networks (EONs). In such a fully shared environment, connection requests (CRs) belonging to different traffic profiles compete for spectral resources. Hence, it is very challenging for network operators to resolve resource conflict that occur at the time of provisioning resources to such CRs. The heterogeneous traffic profile (HTP) considered in this work includes permanent lightpath demands (PLDs) and scheduled lightpath demands (SLDs). We propose various distance adaptive routing and spectrum assignment (DA-RSA) heuristics to resolve resource conflict among these two traffic profiles in EONs under a full sharing environment. Conventionally, preemption was the only technique to resolve such resource conflict among HTPs. Since preemption involves the overhead of selecting CRs to be preempted and then deallocating the resources given to those CRs, excessive preemption adversely affects the performance of the network. Therefore, in this work, we utilized bandwidth splitting as a solution to resolve resource conflict among HTPs under such a shared environment in EONs. Moreover, an integrated solution consisting of splitting and preemption is also proposed. We refer to this new integration as flow-based preemption. Our simulation results demonstrate that bandwidth splitting-based heuristics yield significant improvement in terms of the amount of bandwidth accepted in the network, link and node utilization ratio, number of transponders utilized and the amount of bandwidth dropped due to preemption. Moreover, the flow-based preemption approach is proved to be superior in performance amongst all proposed strategies.

     

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.     

Distributed Nonlinear Integer Optimization for Data-Optical Internetworking

We present a novel approach for joint optical network provisioning and Internet protocol (IP) traffic engineering, in which the IP and optical networks collaboratively optimize a combined objective of network performance and lightpath provisioning cost. We develop a framework for distributed multilayer optimization. Our framework is built upon the IP-over-optical (IPO) overlay model, where each network domain has a limited view of the other. Our formulation allows the two domains to communicate and coordinate their decisions through minimal information exchange. Our solution is based on a novel application of Generalized Bender's Decomposition, which divides a difficult global optimization problem into tractable subproblems, each solved by a different domain. The procedure is iterative and converges to the global optimum. We present case studies to demonstrate the efficiency and applicability of our approach in various networking scenarios. Our work builds a foundation for “multilayer” grooming, which extends traditional grooming in the optical domain to include data networks. The data networks are active participants in the grooming process with intelligent homing of data traffic to optical gateways.     

Joint scheduling and virtual topology design for sliding periodic traffic

Two possible approaches can be considered for solving the virtual topology design problem for periodic (multi-hour) traffic demands. The first approach attempts to design a static topology that can accommodate all the traffic variations over time. The second option is to determine an appropriate series of virtual topologies to accommodate the different traffic loads at different times. This can lead to some savings in terms of the number of transceivers needed, but it requires the use of costly reconfigurable switching equipment. So, strategies for stable virtual topology design have received considerable attention in recent years. However, all the works reported in the literature so far, focus on the fixed window scheduled traffic model, where the start and end times of the demands are known in advance. In this paper, we propose a new integrated approach using the more general sliding window model, for jointly scheduling the demands in time and designing a logical topology that can accommodate all the scheduled demands. The goal is to a find a suitable static topology that can handle fluctuations in the offered sub-wavelength traffic load, without requiring the use of reconfigurable optical switching equipment. We first present a comprehensive integer linear program (ILP) formulation for designing a cost-efficient, stable logical topology for time-varying demands, and then propose an integrated heuristic algorithm capable of handling larger networks. Simulation results demonstrate the advantages of the proposed approaches, not only compared to holding time unaware models, but also over the traditional fixed window model.     

Improved Dynamic Lightpath Provisioning for Large Wavelength-Division Multiplexed Backbones

Technology already exists that would allow future optical networks to support automatic lightpath configuration in response to dynamic traffic demands. Given appropriate commercial drivers, it is possible to foresee carrier network operators migrating away from semipermanent provisioning to enable on-demand short-duration communications. However, with traditional lightpath reservation protocols, a portion of the lightpath is idly held during the signaling propagation phase, which can significantly reduce the lightpath bandwidth efficiency in large wavelength-division multiplexed backbones. This paper proposes a prebooking mechanism to improve the lightpath efficiency over traditional reactive two-way reservation protocols, consequently liberating network resources to support higher traffic loads. The prebooking mechanism predicts the time when the traffic will appear at the optical cross connects, and intelligently schedules the lightpath components such that resources are only consumed as necessary. We describe the proposed signaling procedure for both centralized and distributed control planes and analyze its performance. This paper also investigates the aggregated flow length characteristics with the self-similar incident traffic and examines the effects of traffic prediction on the blocking probability as well as the ability to support latency sensitive traffic in a wide-area environment.     

Experimental GMPLS-based provisioning for future all-optical DPRing-based MAN

Given the abundance and strategic importance of ring fiber plants in metropolitan area networks (MANs), and the accelerating growth of Internet traffic, it is crucial to extend the existing Internet protocol (IP)-based generalized multiprotocol label switching (GMPLS) framework to provision dynamic wavelength division multiplexing (WDM) optical rings. Nevertheless, the emerging GMPLS-based lightpath provisioning does not cover the intricacies of optical rings. No GMPLS standard exists for optical add-drop multiplexer (OADM) rings, relying instead upon proprietary static solution. The objective of this paper is to propose and evaluate novel GMPLS-based lightpath signaling and wavelength reservation schemes specifically designed for dedicated protection ring (DPRing)-based MANs. Performance evaluation has been carried out in a GMPLS-based testbed named ADRENALINE.     

IPoverWDM光网络中基于滑动调度业务模型的节能业务量疏导算法研究(英文)

In this paper,we investigate on the problem of energy-efficient traffic grooming under sliding scheduled traffic model for IP over WDM optical networks,so as to minimize the total energy consumption of the core network.We present a two-layer auxiliary graph model and propose a new energyefficient traffic grooming heuristic named Two-Dimension Green Traffic Grooming(TDGTG) algorithm,which takes both space and time factors into consideration for network energy efficiency.We compare our proposed TDGTG algorithm with the previous traffic grooming algorithms for scheduled traffic model in terms of total energy consumption and blocking probability.The simulation results in three typical carrier topologies show the efficiency of our proposed TDGTD algorithm.     

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.     

Routing Algorithms in WDM Networks under Mixed Static and Dynamic Lambda-Traffic

Dynamic traffic is becoming important in WDM networks. In the transition towards full dynamic traffic, WDM networks optimized for a specific set of static connections will most likely also be used to support on-demand lightpath provisioning. Our paper investigates the issue of routing of dynamic connections in WDM networks which are also loaded with high-priority protected static connections. By discrete-event simulation we compare various routing strategies in terms of blocking probability and we propose a new heuristic algorithm based on an occupancy cost function which takes several possible causes of blocking into account. The behavior of this algorithm is tested in well-known case-study mesh networks, with and without wavelength conversion. Moreover, Poissonian and non-Poissonian dynamic traffics are considered.     

Optical resources provisioning: multipoint‐to‐point lightpaths mapping in all‐optical networks

In wavelength‐division multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming low‐speed connections onto high‐capacity lightpaths will improve the network throughput and reduce the network cost. In this paper, we propose and evaluate a new concept of traffic aggregation in WDM mesh networks that aims to eliminate both the bandwidth under‐utilization and scalability concerns that are typical in all‐optical wavelength routed networks. This approach relies on the multipoint‐to‐point lightpath concept. In order to assess the efficiency of our proposal, all underlying network costs are compared. To achieve this aim, we devise a new provisioning algorithm to map the multipoint‐to‐point lightpaths in the network. Our results show that the proposed aggregation technique can significantly improve the network throughput while reducing its cost. Copyright © 2005 John Wiley & Sons, Ltd.     

Algorithms for multicast traffic grooming in WDM mesh networks

Several of the new applications in high-performance networks are of the multicast traffic type. Since such networks employ an optical network infrastructure, and since most of these applications require subwavelength bandwidth, several streams are usually groomed on the same wavelength. This article presents an account of recent advances in the design of optical networks for multicast traffic grooming in WDM mesh networks. The article addresses network design and session provisioning under both static and dynamic multicast traffic. Under static traffic conditions, the objective is to accommodate a given set of multicast traffic demands, while minimizing the implementation cost. Optimal and heuristic solution techniques for mesh network topologies are presented. Under dynamic traffic conditions, techniques for dynamic routing and session provisioning of multicast sessions whose objective is to minimize session blocking probabilities are explained. The article also presents a number of open research issues     

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.     

On service provisioning using light-trails in WDM optical networks with waveband switching

As the number of wavelengths in a single optical fiber increases, so does the number of ports needed for wavelength switching in optical cross-connects (OXCs), which may significantly increase the cost and difficulty associated with controlling large OXCs. Waveband switching (WBS) treats several wavelengths as a bundle that is switched through a single port if they share the same switch route, so that the number of ports needed can be reduced. On the other hand, light-trails in wavelength division multiplexing (WDM) optical networks allow intermediate nodes on established optical paths to access the data paths whereas light-paths only allow two end nodes to access the data paths. Therefore, light-trails offer significantly better flexibility for service provisioning and traffic grooming. In this article, we study service provisioning using light-trails in WDM optical networks with the WBS capability under a static traffic model. For comparison, integer linear programs are formulated for establishing light-trails with and without WBS. Numerical studies show that in certain cases, service provisioning with WBS in light-trail networks can reduce the number of ports needed while providing a more flexible sub-wavelength service provisioning capability. However, contrary to intuition, in most cases applying the WBS technique requires more ports in OXCs in light-trail networks. This study provides insights into the network design problem that applies the WBS technology to light-trail based optical networks.     

A Lagrangean relaxation based near-optimal algorithm for advance lightpath reservation in WDM networks

Advance lightpath reservation is a new research topic for connecting high-speed computer servers in lambda grid applications and for dynamic lightpath provisioning in the future optical internet. In such networks, users make call requests in advance to reserve network resources for communications. The challenge of the problem comes from how to jointly determine call admission control, lightpath routing, and wavelength assignment. In this paper, we propose an efficient Lagrangean relaxation (LGR) approach to resolve advance lightpath reservation for multi-wavelength optical networks. The task is first formulated as a combinatorial optimization problem in which the revenue from accepting call requests is to be maximized. The LGR approach performs constraint relaxation and derives an upper-bound solution index according to a set of Lagrangean multipliers generated through subgradient-based iterations. In parallel, using the generated Lagrangean multipliers, the LGR approach employs a new heuristic algorithm to arrive at a near-optimal solution. By upper bounds, we assess the performance of LGR with respect to solution accuracy. We further draw comparisons between LGR and three heuristic algorithms—Greedy, First Come First Serve, and Deadline First, via experiments over the widely-used NSFNET network. Numerical results demonstrate that LGR outperforms the other three heuristic approaches in gaining more revenue by receiving more call requests.     

Efficient Protection in MPλS Networks Using Backup Trees: Part One—Concepts and Heuristics

Multi-protocol lambda switching (MPS) has recently been applied in the optical network control plane to provide fast lightpath provisioning. As an increasing amount of traffic is carried in optical transport networks (OTNs), single network failures can affect a vast amount of traffic, making lightpath protection crucial. Therefore, shared backup tree (BT) lightpath protection is a promising paradigm in MPS networks due to its ability of fast recovery and its efficiency in consumed resources. A shared BT is used to protect a group of working lightpaths towards the same destination. From the working lightpaths in such a group, only one affected lightpath at a time can be recovered using the BT. The main problem is how to group and route the working paths (WPs) and how to route the BTs, in such a way that the capacity resources used by the WPs and the BTs are minimized. In Part One of this study (presented in this paper), we propose three approaches to cope with this problem. The first approach is a purely integer linear programming (ILP) based method. The second one is a combination of ILP and a heuristic technique. The last one is a purely heuristic approach. In this paper, these approaches are theoretically compared. In Part Two [1] of this study, several simulations are carried out in order to compare these approaches in terms of performance and computing effort. The experimental results are in line with the theoretical expectations.     

Subpath protection for scalability and fast recovery in optical WDM mesh networks

This paper investigates survivable lightpath provisioning and fast protection switching for generic mesh-based optical networks employing wavelength-division multiplexing (WDM). We propose subpath protection, which is a generalization of shared-path protection. The main ideas of subpath protection are: 1) to partition a large optical network into smaller domains and 2) to apply shared-path protection to the optical network such that an intradomain lightpath does not use resources of other domains and the primary/backup paths of an interdomain lightpath exit a domain (and enter another domain) through a common domain-border node. We mathematically formulate the routing and wavelength-assignment (RWA) problem under subpath protection for a given set of lightpath requests, prove that the problem is NP-complete, and develop a heuristic to find efficient solutions. Comparisons between subpath protection and shared-path protection on a nationwide network with dozens of wavelengths per fiber show that, for a modest sacrifice in resource utilization, subpath protection achieves improved survivability, much higher scalability, and significantly reduced fault-recovery time.     

From network design to dynamic provisioning and restoration inoptical cross-connect mesh networks: an architectural and algorithmicoverview

This article presents a broad overview of the architectural and algorithmic aspects involved in deploying an optical cross-connect mesh network, starting from the network design and capacity planning phase to the real-time network operation phase involving dynamic provisioning and restoration of lightpaths and online algorithms for route computation. Frameworks for offline design and capacity planning of optical networks based on projected future lightpath demands are discussed. The essential components of an IP-centric control architecture for dynamic provisioning and restoration of lightpaths in optical networks are outlined. These include neighbor discovery, topology discovery, route computation, lightpath establishment, and lightpath restoration. Online algorithms for route computation of unprotected, 1+1 protected and mesh-restored lightpaths are discussed in both the centralized and distributed scenarios