Dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes

The wavelength selective switch-based reconfigurable optical add/drop multiplexers is a promising switching equipment for future reconfigurable wavelength-division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment problem. In an asymmetric switching scenario, using the classic Dijkstra’s algorithm can lead to invalid paths traversing unconnected ports of an asymmetric node. To solve this problem, we propose both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes. The proposed LS schemes include the asymmetric switching-aware (ASA) Dijkstra’s algorithm, the $K$ -shortest path-based algorithm, and the entire path searching (EPS) algorithm. Simulation results show that the ASA-Dijkstra’s algorithm will bring notable improvement of the blocking performance with low computational complexity, while the EPS algorithm has much higher complexity and is not suitable to be employed in large-scale networks. On the other hand, our proposed DV solution, i.e., the information diffusion-based routing (IDBR), can achieve the lowest blocking probability with the lowest computational complexity. Moreover, IDBR does not require the distribution of local asymmetric switching information like the LS schemes, thus having a high level of topology confidentiality.     

Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.     

摆脱光网络配置瓶颈

光网络运营商还没有打破所谓的“配置瓶颈”。他们已经努力地满足了物理传输和部署具有前所未有的端口密度和吞吐量的硬件平台的需求。但是许多运营商还是低估了在一个多厂商（或多业务）的环境中配置业务的复杂度。光速配置要想充分利用光技术的优点，运营商就必须要实现光网络中电路的自动化配置。从一个统一的配置系统对环形或格形的多运营商接入城域网和长途网进行端到端的电路配置的能力对于提供持久的竞争优势是十分关键的。在城域网和长途网中，运营商正在对SONET环进行升级以支持日益增加的带宽需求。运营商正在广泛地大力部署DW…     

Differentiated-resilience provisioning for the wavelength-routed optical network

This paper evaluates the performance of a new scheme for the differentiated-resilience provisioning of lightpaths in a wavelength-routed optical network. A novel differentiated-resilience optical-services model (DROSM) is proposed to enhance the performance of the optical network. First, an analysis of optical-resilience options is presented. Then, a classification of optical services according to their resilience requirement is proposed with respective resilience options. In particular, a novel link-management mechanism is proposed to assist the routing and wavelength allocation. Our numerical results show that differentiated-resilience provisioning has significant merit over that of single resilience provisioning in the optical network.     

Consideration of node failures in network-reliability calculation

Terminal-pair reliability is a common measure of telecommunication network reliability, and many algorithms for calculating it have been published. Most such algorithms presume perfect nodes; although some have presumed imperfect nodes. This paper presents a very simple, uncomplicated way to account for imperfect nodes     

Capacity performance of dynamic provisioning in optical networks

This paper describes an architecture and analyzes the performance of dynamic provisioning of lightpaths in an optical network. In dynamic provisioning, a lightpath is set up in real-time without rearranging the working and protection routes of existing lightpaths, and without the knowledge of future lightpath provisioning events. This paper develops a general model of the physical topology of the optical network, and outlines routing approaches for dynamic provisioning of lightpaths. It analyzes via simulations the performance of dynamically provisioned unprotected, 1+1 protected and mesh-restored lightpaths. The analysis of the efficiency of network utilization of dynamic provisioning focuses on the spare capacity needed for protection, and in particular focuses on the impact of sharing of wavelength channels for mesh-restored lightpaths. The main conclusion from the performance studies is that significant capacity gains are achieved with sharing of wavelength-channels for mesh-restored lightpaths with dynamic provisioning even for sparse topologies, and even at moderate loads     

Service level agreement and provisioning in optical networks

This article proposes a service level agreement applied to the optical domain (O-SLA), which is expected to be the near- and long-term network technology of the great bandwidth capacity offered by optical devices. After an exposition of the rationale behind an optical SLA, parameters that could be included in this O-SLA, as well as their values for four classes of services are proposed. Different client (wavelength or subwavelength) and service types (from leased wavelength to bandwidth on demand) are distinguished when necessary. The last part of this article presents issues related to the provisioning of services emanating from this O-SLA.     

Power-aware virtual optical network provisioning in flexible bandwidth optical networks [Invited]

Considering the virtual network infrastructure as a service, optical network virtualization can facilitate the physical infrastructure sharing among different clients and applications that require optical network resources. Obviously, mapping multiple virtual network infrastructures onto the same physical network infrastructure is one of the greatest challenges related to optical network virtualization in flexible bandwidth optical networks. In order to efficiently address the virtual optical network (VON) provisioning problem, we can first obtain the virtual links’ order and the virtual nodes’ order based on their characteristics, such as the bandwidth requirement on virtual links and computing resources on virtual nodes. We then preconfigure the primary and backup paths for all node-pairs in the physical optical network, and the auxiliary graph is constructed by preconfiguring primary and backup paths. Two VON mapping approaches that include the power-aware virtual-links mapping (PVLM) approach and the power-aware virtual-nodes mapping (PVNM) approach are developed to reduce power consumption for a given set of VONs in flexible bandwidth optical networks with the distributed data centers. Simulation results show that our proposed PVLM approach can greatly reduce power consumption and save spectrum resources compared to the PVNM approach for the single-line rate and the mixed-line rate in flexible bandwidth optical networks with the distributed data centers.     

On optimizing the location update costs in the presence of database failures

This paper studies the database failure recovery procedure for cellular phone networks as part of the Electronic Industries Association/Telecommunications Industry Association Interim Standard 41 (EIA/TIA IS-41). Before the location information of the database is recovered, phone calls may be lost. The restoration process can be sped up by having the mobile phones to periodically confirm their existence by radio contact with the cellular network. We show that, under some cost assumptions, periodic update interval should be chosen to be approximately equal to the call interarrival time, with more frequent updates for more unreliable system. We also show that the cost of an optimized system is relatively small and stable, if the system is even moderately reliable. Finally, if the system is at least moderately reliable, the effects of call origination rate and the rate at which Location Areas are crossed, are rather small, assuming that the periodic update interval was chosen as stated above. Thus, in such cases, optimization of the size of the Location Area can be made independent of the optimization of the periodic update process.     

Efficient resource provisioning using traffic balancing in multidomain optical networks

In multidomain optical networks (MDONs) the emerging multimedia, multivendor applications–based scheduled traffic (ST) is periodic and repeated day by day. The traffic is heavy during the working hours and slack during the non‐office hours. This results in the scarcity of network resources during the working hours, leading to the increased blocking of requests, even though there remains relatively large underused capacity during the non‐office hours. To use the network resources uniformly and efficiently, the demands may be slided within or shifted along the time zones/windows. In this paper, we first propose a heuristic algorithm, time‐aware routing and wavelength assignment (TA‐RWA), which allocates resources without traffic balancing (TB) for the ST in MDON. Time‐aware routing and wavelength assignment policy is then used as a benchmark for comparison with the 3 different TB solutions (named as P1‐TB, P2‐TB, and P3‐TB), in which the network load is redistributed by rescheduling the intradomain and interdomain demands. We performed extensive simulation experiments in MATLAB environment and compared the proposed policies with the existing ordering policies. From the results, it can be inferred that the proposed TB policies outperform the TA‐RWA, and the existing strategies of the blocking probability, resource utilization ratio (RUR), and percentage of intradomain and interdomain connections established. The best performance is achieved using P3‐TB strategy, in which requests are slided within, and shifted, along different time windows. The strategy shows about 70% reduction in the percentage blocking probability with respect to the TA‐RWA and the existing strategies.     

Toward automated provisioning of advance reservation service in next-generation optical internet

The Internet is expected to support a variety of network services for its vast individual and business users. Advance reservation is a promising network service in which network resources are automatically allocated and reserved in advance of the time the resources are actually needed, which allows service providers to more efficiently manage network resources and thus provide better network services. For the next-generation Internet, the underlying transport infrastructure is evolving towards a network that integrates fiber-optic technology and generalized multi-protocol label switching (GMPLS) technology. In this article we present a basic framework for automated provisioning of advance reservation service in the next-generation optical Internet, discuss the major issues involved, and explore possible solutions. It is also our hope to stimulate further studies in order to realize the vision of this promising network service     

基于RSVP-TE信令的GMPLS动态性能研究

主要介绍通用多协议标签交换信令性能及测试的相关工作.指出目前急需对多协议标签交换动态性能进行描述,并提出了一组多协议标签交换动态性能参数以期能对网络运营商、设备制造商和应用程序设计者有一定的帮助.最后给出了在现有多协议标签交换光网络平台上的测试结果并对其进行了分析,并讨论了进一步的研究方向.     

Dynamic circuit provisioning in all-optical WDM networks using lightpath switching

In this paper we investigate the problem of provisioning holding-time-aware (HTA) dynamic circuits in all-optical wavelength division multiplexed (WDM) networks. We employ a technique called lightpath switching (LPS) wherein the data transmission may begin on one lightpath and switch to a different lightpath at a later time. Lightpath switches are transparent to the user and are managed by the network. Allowing LPS creates a number of segments that can use independent lightpaths. We first compare the performance of traditional routing and wavelength (RWA) assignment to routing and wavelength assignment with LPS. We show that LPS can significantly reduce blocking compared to traditional RWA. We then address the problem of routing dynamic anycast HTA dynamic circuits. We propose two heuristics to solve the anycast RWA problem: anycast with continuous segment (ACS) and anycast with lightpath switching (ALPS). In ALPS we exercise LPS, and provision a connection request by searching for the best candidate destination node is such a way that the network resources are utilized efficiently. In ACS we do not allow a connection request to switch lightpaths. The lightpaths to each candidate destination node of a request are computed using traditional RWA algorithms. We first compare the performance of ACS to ALPS and observe that ALPS achieves better blocking than ACS. Furthermore, we also compare the performance of these two anycast RWA algorithms to the traditional unicast RWA algorithm. We show that the anycast RWA algorithms presented here significantly outperform the traditional unicast RWA algorithms.     

损伤感知的光网络连接指配的关键问题研究

在透明网络中,光信号由于受到物理损伤的影响而质量降低,这使得损伤感知的连接指配日益成为人们研究的热点.文章从架构、损伤模型和损伤感知的路由波长分配(IRWA)算法3方面研究了损伤感知的光网络连接指配的     

Computer simulation of integrated circuits in the presence of electrothermal interaction

A computer program which predicts the DC and transient performance of monolithic integrated circuits in the presence of electrothermal interactions on the integrated circuit die is described. The thermal modeling of the die/package structure and the numerical analysis procedure is discussed. Experimental and simulation results are compared for monolithic operational amplifiers, voltage regulators, and a temperature-stabilized voltage reference.     

Power-aware provisioning strategy with shared path protection in optical WDM networks

As the Internet continues to grow, the power consumption of telecommunication networks is rising at a considerable speed, which seriously increases the operational expenditure and greenhouse gas emission. Since optical Wavelength Division Multiplexing (WDM) networks are currently the most promising network infrastructures, power saving issue on these networks has received more attention in recent years. In traditional optical WDM networks, a large amount of power is drained by the redundant idle resources and reserved backup resources although these powered on resources do not carry traffic in most of the time. In order to reduce the network power consumption, turning off the corresponding network components or switching them to a low-power, standby state (or called sleep mode) is a promising greening approach. In this paper, we study the power-aware provisioning strategies and propose a sleep mode based Power-Aware Shared Path Protection (PASPP) heuristic algorithm to achieve the power efficiency of optical WDM networks. By jointly utilizing link-cost and fiber-cost in path routing, resource assignment, and resource release, PASPP makes working paths and backup paths converge on different fibers as much as possible, and switch idle and backup components to sleep mode to realize power saving. Simulation results show that our PASPP can obtain notable power saving and achieve satisfactory tradeoff between power efficiency and blocking probability with respect to Power-Unaware Shared Path Protection (PUSPP).     

Online connection provisioning in metro optical WDM networks using reconfigurable OADMs

Optical add/drop multiplexers (OADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) ring networks by allowing traffic to bypass intermediate nodes without expensive opto-electro-opto (O-E-O) conversion. Some traditional OADMs, called fixed OADMs (FOADMs), can only add/drop traffic on a specific wavelength. Reconfigurable OADMs (ROADMs) are emerging, which can add/drop traffic onto/from different wavelengths at different time. ROADMs provide desirable flexibility, enable fast provisioning of dynamic traffic, and save capital expenditure (CapEx) and operational expenditure (OpEx). In order to be cost effective, some ROADMs employ architectures that tune the ROADM continuously from one wavelength to another, crossing through all the wavelengths in between, which may cause interference to the connections, if any, on those wavelengths being crossed. In order to prevent existing connections from being interrupted, a constraint needs to be imposed that ROADMs cannot cross working wavelengths when tuning. In this paper, the design and the benefits of metro optical WDM network architectures using ROADMs and the impact of this tuning constraint on the performance of the network are investigated. The dynamic traffic provisioning problem is analyzed and divided into two subproblems: 1) a traditional one on resource allocation; and 2) a new subproblem on tuning-head positioning (TP). Several heuristics for each subproblem are developed to combat the tuning constraint. Results from our simulation experiments show that the tuning constraint can significantly affect the network performance in terms of overall connection blocking probability, and good heuristics for network control and management are needed to overcome this tuning constraint.     

Connection provisioning with guaranteed recovery time in survivable WDM optical networks

Optical networks employing wavelength- division multiplexing (WDM) are prone to failures. In case of a failure, the time to recovery is an important metric, since the amount of lost information and the performance of carried application strongly depends on the time of service interruption. Moreover, as the current trend in network development is moving toward a unified solution providing support for voice, data and various multimedia services, different application and users may tolerate different time of service interruption. Therefore, it is imperative to provide recovery-time guaranteed connections in WDM optical networks. In this paper, we propose a new shared-segment protection algorithm, called AGBSP-QoP, to provision connection requests according to their differentiated recovery-time requirements. Given a working path, AGBSP-QoP first computes all possible recovery-time guaranteed working-backup segment pairs, and then dynamically selects a least-cost eligible subset based on a dexterously constructed auxiliary graph. We conduct simulations under single class of service and multiple classes of service, and compare AGBSP-QoP with other protection algorithms. The results show that AGBSP-QoP yields the best performance and can properly provision connection requests according to their differentiated recovery-time requirements.