Impairment-Aware Dynamic Routing and Wavelength Assignment in Translucent Optical WDM Networks

Routing and wavelength assignment (RWA) is a widely discussed design problem in the optical networks literature. Physical layer impairments (PLI) degrade the quality of transmission (QOT) of a propagating optical signal inside the optical fiber and they have a significant impact on the RWA process. 3R regeneration, which is based on the expensive optical-to-electronic-to-optical (OEO) conversion technology, is a popularly used technique to restore the degraded QOT of an optical signal. In order to minimize both capital and operational costs, it is highly desirable to use a translucent optical network, in which the 3R regenerators are sparsely yet strategically placed. This thesis presents a novel impairment-aware RWA approach, called best first search RWA (BFS-RWA), for dynamic connection requests, in a translucent optical network. BFS-RWA is based on the A* best first search algorithm and guarantees an optimal solution (i.e. using the least possible number of regenerators)

Optimal Regenerator Placement for Dedicated Path Protection in Impairment-Aware WDM Networks

Building resilient Wavelength Division Multiplexed (WDM) optical networks is an important area of research. This thesis deals with the design of reliable WDM networks where physical layer impairments are taken into account. This research addresses both the regenerator placement problem (RPP) and the routing with regenerator problem (RRP) in impairment-aware WDM networks, using dedicated path protection. Both the problems have been tackled using linear Integer formulations which can be implemented, using a solver such as the CPLEX. For solving RPP, two solutions have been proposed - i) a formulation that gives optimal solutions which works only for small networks, and ii) a highly effective heuristic which given an optimal solution in 97.5 to 99% of cases for networks having a size up to 60 nodes

A Survey on the Path Computation Element (PCE) Architecture

Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits

Survivability aspects of future optical backbone networks

In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie

A New Parametric Regenerator Allocation Scheme taking into account Inaccurate Physical Information

Regenerator allocation consists on selecting which of the already installed regenerators in a translucent network may be used according to the dynamic traffic requests in order to maximize the quality of the optical signal while minimizing the opaqueness of the network. A recent study has shown that the performance of the regenerator allocation techniques strongly depends on the accuracy of the physical-layer information. The reason of this physical inaccuracy is the drift suffered by the physical-layer parameters during the operation of the optical network. In these conditions, the performance of the Impairment Aware-Routing and Wavelength Assignment (IA-RWA) process might drop sharply when allocating regenerators inappropriately. In this paper, we propose new regenerator allocation schemes taking into account the inherent and unavoidable inaccuracy in the physical-layer informationPostprint (published version

Impairment-Aware Design of Translucent DWDM Networks Based on the k-Path Connectivity Graph

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Impairment Aware Routing in Translucent Optical Networks

Optical networks are ideally suited to meet today\u27s rapidly increasing bandwidth demands due to the large fiber bandwidth capacity, low attenuation, low distortion and low cost. When an optical signal propagates along the fiber links, its quality degrades due to physical layer impairments such as optical noise, chromatic dispersion, polarization mode dispersion and nonlinear effects. As a result, bit error rate (BER) may become so high that signal may not be properly detected at the receiver. In order to address this problem, we have developed an impairment aware dynamic routing and wavelength assignment (IA-RWA) algorithm. Our algorithm not only takes into account the physical layer impairments but also resolves any wavelength conflict if there is a cycle in the path from a source to a destination. Our results indicate that the proposed algorithm significantly reduce the blocking probability in dynamic lightpath allocation if the impact of physical layer impairments is compensated by the use of regenerators

IMPAIRMENT AWARE DYNAMIC ROUTING AND WAVELENGTH ASSIGNMENT IN WDM NETWORKS

Optical networks play a major role in supporting the traffic in backbone computer networks. Routing and Wavelength Assignment (RWA) is the technique used to establish a light-path from a source node to a destination node in a Wavelength Division Multiplexed (WDM) optical network. As an optical signal propagates through the network, the quality of the signal degrades due to physical layer impairments. To address this problem, in translucent WDM networks, the signal is regenerated at intervals. The main objective of this research is to propose a fast heuristic for dynamic lightpath allocation in translucent WDM networks and to compare the heuristic with an optimal algorithm that was proposed recently