Dynamic Lightpath Establishment Research Articles

Minimizing Cost of Regeneration at Regeneration Sites–A New Approach for Dynamic Lightpath Establishment in Translucent Optical Networks

Lightpaths in translucent optical networks have to undergo regeneration at certain nodes designated as regeneration sites to maintain its quality of transmission. Regenerating an optical signal necessitates optical-electronic-optical conversion and is thus a costly affair due to use of regeneration resources. Thus minimizing the cost of regeneration in such networks is vital. Minimizing cost of regeneration leads to two different problems; 1) the problem of minimizing the total cost of regeneration for the connections served and 2) the problem of minimizing the cost of regeneration at regeneration sites while serving the connections. The previous works on lightpath establishment in such networks have mostly addressed the first problem. In this paper we study the second problem i.e. the problem of minimizing the cost of regeneration at regeneration sites during dynamic establishment of lightpaths. As the problem is NP-Complete, we propose an Integer Linear Program for small networks and then propose two heuristic routing approaches for large networks. Time complexity analysis shows that our heuristic algorithms run in polynomial time. Extensive simulation experiments reveal that our approaches are not only efficient to address the problem but can also provide better blocking performance when regeneration resources are scarcely deployed at regeneration sites.

RWA: Optical Networks with Heuristics Algorithms

El aumento de la demanda en el transporte de datos a través de las redes ópticas WDM (Wavelength Division Multiplexing) ha llevado a nuevos problemas relacionados con la búsqueda de rutas y la asignación de longitudes de onda en estas redes, estos problemas se resuelven a través de procesos algorítmicos que pueden ser convencionales o heurísticos. Los algoritmos convencionales sólo satisfacen los requerimientos en condiciones de tráfico estático. Sin embargo, los algoritmos heurísticos pueden ser procesados en escenarios de tráfico dinámico. Este documento propone una estrategia global para hacer frente al DLE (Establecimiento de Caminos de Luz dinámicos), es decir, sin dividir el problema, utilizando varios algoritmos heurísticos. Los resultados mostrados indican que los algoritmos heurísticos responden mejor bajo estrés en escenarios dinámicos, pero con un uso de la red alto.

Design of low power all-optical networks with dynamic lightpath establishment

In multifiber all-optical networks, optical amplifiers are used for amplifying multiple optical signals with different wavelengths in fibers. An optical amplifier operates when any of light-paths passes through it. Therefore, it should simultaneously amplify as many lightpaths as possible for efficiently utilizing its power. This paper proposes a dynamic lightpath establishment scheme considering the use efficiency of the optical amplifiers and the depletion of the wavelength resources in multifiber all-optical networks. The proposed scheme provides a routing and wavelength assignment strategy that reduces both the power consumption of the optical amplifiers and the blocking probability of the lightpath establishment. Through simulation experiments, we demonstrate the effectiveness of the proposed scheme.

Dynamic Lightpath Establishment Considering Four‐Wave Mixing for Achieving Low‐Power All‐Optical Networks

SUMMARYThis paper proposes a method for dynamically establishing a lightpath that takes into consideration power consumption and four‐wave mixing (FWM) in an all‐optical network. In an all‐optical network, an optical fiber amplifier is used to amplify a group of optical signals of different wavelengths in a fiber without O/E/O conversion. Even if only one optical signal passes through an optical fiber amplifier in a fiber, the optical fiber amplifier operates. Thus, to efficiently use the power of an optical fiber amplifier, multiple optical signals in the fiber should be simultaneously amplified. FWM is one of the most important physical impediments to be resolved an in all‐optical network because FWM degrades the performance of such networks. The FWM power in a fiber increases with the number of wavelengths used in the fiber. Therefore, in order to reduce the FWM power, it is preferable to have optical signals be transmitted on different fibers. The proposed method provides an ingenious path, wavelength, and fiber selection strategy that takes the trade‐off between power consumption and FWM power into account. Furthermore, the proposed method avoids blocking of lightpath establishment due to depletion of wavelength resources. Through simulation experiments, we show that the proposed method can efficiently reduce the blocking probability, power consumption, and FWM power when the number of fibers is fixed.

Experimental assessment of a cognitive mechanism to reduce the impact of outdated TEDs in optical networks

We have recently proposed and demonstrated, by means of simulation, the benefits of a simple yet effective cognitive technique to enhance stateless Path Computation Element algorithms with the aim of reducing the connection blocking probability when relying on a potentially non-up-to-date traffic engineering database. In this paper, we employ that technique, called elapsed time matrix (ETM), in the framework of the CHRON (Cognitive Heterogeneous Reconfigurable Optical Network) architecture and, more importantly, validate and analyze its performance in an emulation environment (rather than in a simulation environment) supporting impairment-aware lightpath establishment. Not only dynamic lightpath establishment on demand has been studied, but also restoration processes when facing optical link failures. Emulation results demonstrate that ETM reduces the blocking probability when establishing lightpaths on demand, and increases the percentage of successful restorations in case of optical link failure. Moreover, the use of that technique has little impact on lightpath setup time and lightpath restoration time, respectively.

Request differentiation in dynamic light-path establishment for WDM routed all optical networks of data centers

Existing routing and wavelength assignment (RWA) solutions try to minimize the blocking rate as the main quality of service (QoS) metric. However, in ultra high-speed all optical interconnection networks of data centers, more important metrics such as network throughput and channel utilization are of interest for network designers. This paper proposes dynamic request buffering routing and wavelength assignment (DRB-RWA) that aims at maximizing the network throughput and total amount of transmitted data in addition to minimizing the blocking rate by proposing a dynamic RWA scheme based on request differentiation. The proposed scheme tries to exploit buffering approach in order to be able to achieve a pseudo static traffic out of a dynamic traffic; and hence, it would be able to differentiate requests in terms of desired metrics. However, conventional dynamic RWA solutions solely aim at minimizing the blocking rate. We evaluate the performance of the proposed algorithm via analytical approach as well as comprehensive simulations to confirm the fact that the network throughput, and therefore, total amount of transmitted data are maximized when the proposed scheme is applied.

Dynamic Resource Management in Optical Grid

In this brief, for optical grid, we propose three dynamic resource management methods. The proposed methods use a dynamic lightpath establishment and release algorithm, and those are implemented in a job manager. Moreover, those methods use three different task transmission controllers so that a resource manager can store a constant number of tasks. The first controller uses a proportional-integral-differential (PID) control to adjust the number of tasks that are transmitted to a computing site. The second controller uses a model predictive control (MPC) based on mixed integer quadratic programming (QP), and the third controller uses an MPC based on QP. Each task transmission controller manages the computing resources, and the dynamic lightpath establishment and release algorithm manages the network resources. We evaluate the performances of the proposed methods with MATLAB and investigate the effectiveness of each method. Numerical examples show that the computing resources and the network resources can be effectively utilized by using our proposed methods. In addition, we show the implementation capabilities of the three methods.

Dynamic Lightpath Establishment Considering Four-Wave Mixing for Achieving Low Power All-optical Networks

This paper proposes a dynamic lightpath establishment scheme considering power consumption and four-wave mixing (FWM) in all-optical networks. In all-optical networks, an optical amplifier is used to amplify a group of optical signals of different wavelengths in a fiber without O/E/O conversion. Even if only one optical signal passes through an optical amplifier in a fiber, the optical amplifier operates. Thus, to efficiently use power of the optical amplifier, multiple optical signals in the fiber should be simultaneously amplified. FWM is one of the most important physical impairments to be resolved in all-optical networks because FWM decays the performance of all-optical networks. The FWM power in a fiber increases with the number of wavelengths used in the fiber. Therefore, in order to reduce the FWM power, it is preferred that optical signals are transmitted on different fibers. The proposed scheme provides an ingenious route, wavelength, fiber selection strategy considering the tradeoff between the power consumption and the FWM power. Furthermore, the proposed scheme avoids blocking of lightpath establishment due to depletion of wavelength resources. Through simulation experiments, we show that the proposed scheme efficiently reduces the blocking probability, the power consumption, and the FWM power in case of the number of fibers is fixed.

Dynamic lightpath establishment considering four-wave mixing in multifiber WDM networks

This paper proposes a dynamic lightpath establishment scheme considering four-wave mixing (FWM) in multifiber wavelength-division multiplexed (WDM) all-optical networks. The FWM is one of the most important physical impairments to be resolved in WDM networks because the FWM induces nonlinear inter-channel crosstalk and decays the performance of WDM networks. In WDM networks, data are transmitted via lightpaths. When the effect of FWM crosstalk is large, it is highly possible that data transmission fails even if lightpaths are correctly established. The proposed scheme aims to avoid not only the blocking of lightpath establishment but also the accumulation of FWM crosstalk by means of ingenious selection of routes, wavelengths, and fibers for lightpath establishment. In the proposed scheme, a route and a wavelength are selected for each lightpath based on wavelength availability and wavelength placement of established lightpaths. Furthermore, fibers on the route are selected based on estimated FWM power. In this paper, we show the effectiveness of the proposed scheme through simulation experiments.

Impairment-aware lightpath provisioning using inverse multiplexing in mixed-line-rate networks

In Mixed-Line-Rate (MLR) networks, different line rates on different wavelengths can coexist on the same fiber. MLR brings flexibility to handle diverse demands by allowing each lightpath to be established end-to-end with different line rates, if necessary. High line rates require advanced modulation techniques, such as DQPSK and DP-QPSK. On the other hand, signals being propagated over transparent paths are exposed to detrimental effects of physical-layer impairments (PLIs). Advanced modulation techniques are highly susceptible to PLI, especially to the cross-phase modulation (XPM) induced by intensity-modulated channels.Inverse multiplexing (IM), in MLR networks, is a technique which exploits the advantage of transmitting the signals with low line rates where the high line rate is not possible due to PLIs.In this study, we propose new algorithms employing IM to account for the impairment-aware dynamic lightpath establishment problem in MLR networks. Experimental results show that our approaches improve the performance in terms of blocking ratio with a cost of additional network resource usage.

Experimental demonstration of OpenFlow-based control plane for elastic lightpath provisioning in Flexi-Grid optical networks

Due to the prominent performance on networking virtualization and programmability, OpenFlow is widely regarded as a promising control plane technology in packet-switched IP networks as well as wavelength-switched optical networks. For the purpose of applying software programmable feature to future optical networks, we propose an OpenFlow-based control plane in Flexi-Grid optical networks. Experimental results demonstrate its feasibility of dynamic lightpath establishment and adjustment via extended OpenFlow protocol. Wireshark captures of the signaling procedure are printed out. Additionally, the overall latency including signaling and hardware for lightpath setup and adjustment is also reported.

Distributed optical control plane for dynamic lightpath establishment in translucent optical networks based on reachability graph

In transparent optical networks, physical layer impairments (PLIs) incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the optical feasibility of the lightpaths. In addition, transparent optical networks suffer from inefficient wavelength utilization, as a connection request may be rejected because of non-availability of a common wavelength on all the links along the chosen route. To increase optical reach, resource utilization, and average call acceptance ratio (and hence revenues), network operators are resort to translucent optical networks. In these networks a limited number of regenerators are placed at a selected set of nodes. In this scenario development of an optical control plane which is aware of PLIs, location and number of regenerators, is of paramount importance for on-demand lightpath provisioning. In this paper, we propose a novel approach of constructing a reachability graph of the physical network considering PLIs and regenerators. If there is no transparent path in the physical network, we route the connections with multiple transparent segments on the reachability graph. We propose efficient mechanisms and corresponding GMPLS protocol extensions for impairment and regenerator aware routing and wavelength assignment (IRA-RWA) in translucent optical networks. The simulation results suggest that our proposed approach together with LSP stitching signaling mechanism is feasible to implement and close to deployment.

Power-Aware Routing and Wavelength Assignment in Multi-Fiber Optical Networks

This paper focuses on the energy consumption minimization problem of an optical transport network extending over a very wide area. In particular, the specific problem of power-aware routing and wavelength assignment (PA-RWA) is addressed considering a transparent multi-fiber optical network. An integer linear programming formulation is provided for the static lightpath establishment problem and a few heuristics are proposed to solve the problem in the case of dynamic lightpath establishment. To solve the routing problem we propose a novel algorithm named load based cost; it is based on a cost function that considers the load of each optical fiber to compute link weights. We also propose two new wavelength assignment algorithms: the first one is derived from the first fit heuristic whilst the second one is based on an innovative approach. It works like a least cost routing algorithm assigning a cost to each wavelength for each link in the path and then minimizes the total cost. Our proposal is compared with a number of already known RWA algorithms showing that it is able to reduce the power consumption of the network by about 20-30%, depending on the amount of traffic treated, with respect to state of the art algorithms with a difference of about 10% with respect to the lower bound. In order to provide a complete analysis of the feasibility of the proposed heuristics, the blocking probability is evaluated: the results show that, unlike the other power-aware algorithms here considered, our proposal shows a low impairment with respect to the least congested path-first fit alternative. Another important result regards the better performance of the proposed wavelength assignment algorithm with respect to first fit.

Light-path establishment with PID control for effective wavelength utilization in all-optical wavelength-division multiplexing networks

We propose a dynamic light-path establishment method for using wavelengths effectively. In our proposed method, a proportional, integral, derivative (PID) controller is implemented in each edge node. The edge node determines the amount of data to be transmitted with PID control so that a constant amount of data can be stored in the buffer. In addition, light paths are established and released dynamically by comparing the output signal of the PID controller with the maximum amount of data that can be transmitted with the established light paths. Because data can be stored in the buffer for a short time, it is expected that the number of established light paths decreases. We evaluate the performance of the proposed method and investigate the impact of the setting parameters. The effectiveness of the proposed method is shown through a comparison with the conventional method.

A path-disjoint approach for blocking probability analysis in hybrid dynamic wavelength routed WDM grooming networks

The present article addresses a novel approach to enhance the overall performance of a WDM optical network. Centralized and distributed approaches for dynamic lightpath establishment are well studied in the literature. Both the approaches have some drawbacks. In this article a hybrid approach is proposed to accept the advantages and discard the disadvantages of both the approaches. With the proposed hybrid approach, a WDM optical network is divided into clusters of nodes. Within a cluster centralized mechanism is applicable whereas connection requests between the node pairs from different clusters follow the distributed mechanism. Also, in this article an analytical model is proposed to compute the expected blocking probability of the proposed hybrid network. First, blocking probabilities for the centralized and distributed approaches are computed and then it is extended for the hybrid approach. The distinguished feature of the proposed analytical model is that it efficiently utilizes the path information of the calls to determine the overall blocking probability of a WDM optical network. It extracts the necessary parameters of a network by simulation and utilize the information to analytically calculate the blocking probability of the network. The NSFNET T1 backbone network is used for the simulation study. To justify the analytical model, the simulation results are compared with that of the analytical model. The simulation results establish the effectiveness of the proposed hybrid approach over the distributed approach in merits of both the call setup time and blocking probability.

Virtual Fiber Configuration for Dynamic Lightpath Establishment in Large-scaled Optical Networks

Recently, progress has been made in the Generalized Multi-Protocol Label Switching (GMPLS) and Automatic Switched Optical Networks (ASON) standardizations. These technologies realize construction of large-scaled optical networks, interconnections among single-domain Wavelength Division Multiplexing (WDM) networks, and direct communication over multi-domain WDM networks. Meanwhile, it is known that the topology of the Internet exhibits the power-law attribute. Since the topology of the Internet, which is constructed by interconnecting ASs, exhibits the power-law, there is a possibility that large-scale WDM networks, which are constructed by interconnecting WDM networks, will also exhibit the power-law attribute. One of the structural properties of a topology that adheres to the power-law is that most nodes have just a few links, although some have a tremendous number of them. Another property is that the average distance between nodes is smaller than in a mesh-like network. A natural question is how such a structural property performs in WDM networks. In this paper, we first investigate the property of the power-law attribute of physical topologies for WDM networks. We compare the performance of WDM networks with mesh-like and power-law topologies, and show that links connected to high-degree nodes are bottlenecks in power-law topologies. To relax this, we introduce a concept of virtual fiber, which consists of two or more fibers, and propose its configuration method to utilize wavelength resources more effectively. We compare performances of power-law networks with and without our method by computer simulations. The results show that our method reduces the blocking probabilities by more than one order of magnitude.

Load balance RWA algorithm using statistical analysis in WDM mesh networks

This study investigates the routing and wavelength assignment (RWA) problem in all-optical wavelength division multiplexing (WDM) mesh networks. The RWA problems can be generally classified as static lightpath establishment (SLE) or dynamic lightpath establishment (DLE). Additionally, the Load Balance RWA (LBRWA) algorithm using the concept of root-mean-square (RMS) which is one of the statistical analysis methods is presented to solve the DLE problem in our study. The proposed algorithm evenly distributes the traffic loads between lightpaths in the RWA process. Simulation results indicate that the proposed algorithm has a lower blocking probability than the Least Loaded Routing algorithm (LLR) and the Maximum Channel Path Routing algorithm (MCPR).

Lightpath setup time optimization in wavelength routed all-optical networks

Wavelength Division Multiplexing (WDM) technology evolved to utilize effectively the enormous bandwidth of optical fiber. In circuit-switched WDM networks data transfer between a given pair of source and destination nodes takes place by using a lightpath. A lightpath is an optical channel having a single wavelength established between the given pair of nodes by configuring the Wavelength Routing Switches (WRS) at the intermediate nodes along the path. In a reconfigurable optical wavelength routing switch, the time required to reconfigure the switch is often long when compared to the speed of data passing through the switch. It is necessary to consider the delay introduced by slow switches as it has significant impact on the performance of the network. In this paper, we present a new technique to mitigate the lightpath setup time overheads in Dynamic Lightpath Establishment (DLE) algorithms for the wavelength continuous circuit switched all-optical networks. Simulation studies indicate that the proposed technique significantly reduces the number of reconfigurations required to setup new lightpaths.

Dynamic lightpath establishment in wavelength routed WDM networks

In wavelength-routed WDM networks, a control mechanism is required to set up and take down all-optical connections. Upon the arrival of a connection request, this mechanism must be able to select a route, assign a wavelength to the connection, and configure the appropriate optical switches in the network. The mechanism must also be able to provide updates to reflect which wavelengths are currently being used on each link so that nodes may make informed routing decisions. In this work, we review control mechanisms proposed in the literature. We also investigate and compare two different distributed control mechanisms for establishing all-optical connections in a wavelength-routed WDM network: an approach based on link-state routing, and one based on distance-vector routing.

Impact of wavelength converters in wavelength routed all-optical networks

This paper attempts to study the impact of wavelength converters in WDM wavelength routed all-optical networks. A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Multihop virtual topology is designed to minimize the number and overall cost of the converters. Blocking probabilities for Static Lightpath Establishment (SLE) and Dynamic Lightpath Establishment (DLE) are analyzed. In the case of SLE, arranging lightpaths in ascending order of their path length reduces blocking probability. Wavelength converters placed at nodes with high nodal degree further reduces the blocking probabilities. Simulation studies performed on 28-node USA long haul network, 20-node arbitrary mesh network, and 19-node EON (European Optical Network) validate the observations made earlier.