Chava Vijaya Saradhi

Experimental Demonstration of an Impairment Aware Network Planning and Operation Tool for Transparent/Translucent Optical Networks

Core optical networks using reconfigurable optical switches and tunable lasers appear to be on the road towards widespread deployment and could evolve to all-optical mesh networks in the coming future. Considering the impact of physical layer impairments in the planning and operation of all-optical (and translucent) networks is the main focus of the Dynamic Impairment Constraint Optical Networking (DICONET) project. The impairment aware network planning and operation tool (NPOT) is the main outcome of DICONET project, which is explained in detail in this paper. The key building blocks of the NPOT, consisting of network description repositories, the physical layer performance evaluator, the impairment aware routing and wavelength assignment engines, the component placement modules, failure handling, and the integration of NPOT in the control plane are the main contributions of this study. Besides, the experimental result of DICONET proposal for centralized and distributed control plane integration schemes and the performance of the failure handling in terms of restoration time is presented in this study.

Differentiated QoS for survivable WDM optical networks

Optical networks based on WDM technology have become a promising solution to realize transport networks that can meet the ever-increasing demand for bandwidth. As WDM networks carry a huge volume of traffic, maintaining a high level of survivability is an important and critical issue. The. development of GMPLS switching technology led to the direct integration of IP and WDM. In these IP-over-WDM networks different applications/end users need different levels of fault tolerance and differ in how much they are willing to pay for the service they get. The current trend in network development is moving toward a unified solution providing support for voice, data, and various multimedia services. Therefore, it imperative that WDM networks incorporate fault tolerance to single or multiple component failures, protection bandwidth, recovery time, and recovery granularity besides resource utilization and call acceptance ratio. This article presents a survey of various methods that have been proposed for providing service differentiation in survivable WDM networks and discuss their performance. Such methods are broadly classified under various paradigms such as differentiated reliability, R-connections, quality of protection, and quality of recovery.

A dynamic impairment-aware networking solution for transparent mesh optical networks

Core networks of the future will have a translucent and eventually transparent optical structure. Ultra-high-speed end-to-end connectivity with high quality of service and high reliability will be realized through the exploitation of optimized protocols and lightpath routing algorithms. These algorithms will complement a flexible control and management plane integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment-aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that will consider dynamic traffic characteristics, a reconfigurable optical layer, and varying physical impairment and component characteristics. The network planning tool along with extended control planes will make it possible to realize the vision of optical transparency. This article presents a novel framework that addresses dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.

Distributed Optical Control Plane Architectures for Handling Transmission Impairments in Transparent Optical Networks

Transmission impairments in wavelength-division- multiplexing (WDM) transparent optical networks accumulate along an optical path and determine the feasibility of lightpaths; hence, the impairments need to be managed efficiently by the control plane. This paper presents impairment-aware distributed optical control plane (OCP) based on enhancements to resource reservation protocol-traffic engineering (RSVP-TE) signaling protocol (S-OCP). In particular, four architectural options [K-sequential (K-SEQ), K-parallel (K-PAR), hop-by-hop (HbH), and full flooding (FF)] within the S-OCP approach are defined and compared. Simulation results show that a combination of HbH routing and feasibility check can be considered as a good compromise both in terms of blocking probability and control plane overhead. The feasibility of a signaling-based approach for the control plane is further demonstrated by comparing simulation results with the results obtained from the implementation of the proposed architectural options in a commercial generalized multiprotocol label switching (GMPLS) protocol emulator. Furthermore, we argue that the real networks will rarely be homogeneous concerning transponder types, creating the need for a transponder selection policy at the end nodes. We introduce and compare two policies: best-first and worst-first. The results obtained from our experiments show that a worst-first policy for selecting transponders can save up to 50% enhanced transponders thereby reducing the overall cost.

Provisioning fault-tolerant scheduled lightpath demands in WDM mesh networks

In this paper, we consider the problem of routing and wavelength assignment (RWA) of fault-tolerant scheduled lightpath demands (FSLDs) in all optical wavelength division multiplexing (WDM) networks under single component failure. In scheduled traffic demands, besides the source, destination, and the number of lightpath demands between a node-pair, their set-up and tear-down times are known, in this paper, we develop integer linear programming (ILP) formulations for dedicated and shared scheduled end-to-end protection schemes under single link/node failure for scheduled traffic demand with two different objective functions: 1) minimize the total capacity required for a given traffic demand while providing 100% protection for all connections; and 2) given a certain capacity, maximize the number of demands accepted while providing 100% protection for accepted connections. The ILP solutions schedule both the primary and end-to-end protection routes and assign wavelengths for the duration of the traffic demands. As the time disjointness that could exist among fault-tolerant scheduled lightpath demands is captured in our formulations, it reduces the amount of global resources required. The numerical results obtained from CPLEX indicate that dedicated scheduled (with set-up and tear-down times) protection provides significant savings (up to 33 %) in capacity utilization over dedicated conventional (without set-up and tear-down times) end-to-end protection scheme; shared scheduled protection provides considerable savings (up to 21 %) in capacity utilization over shared conventional end-to-end protection schemes. Also the numerical results indicate that shared scheduled protection achieves the best performance followed by dedicated scheduled protection scheme, and shared conventional end-to-end protection in terms of the number of requests accepted, for a given network capacity.

Experimental demonstration of centralized and distributed impairment-aware control plane schemes for dynamic transparent optical networks

We demonstrate and compare distributed and centralized impairment-aware control plane schemes for transparent optical networks with dynamic traffic. Experimental results show that distributed scheme yields one fifth of setup time required by previously reported alternatives.

Scheduling and Routing of Sliding Scheduled Lightpath Demands in WDM Optical Networks

We develop a time conflict resolving window division algorithm which places a given set of sliding scheduled lightpath demands within their allowed interval and two routing and wavelength assignment (RWA) algorithms, and study their performance.

Practical and deployment issues to be considered in regenerator placement and operation of translucent optical networks

In translucent optical networks, the signal will remain in the optical domain as long as possible and will be regenerated only when its quality falls below a threshold or a wavelength contention has to be resolved. In these networks a limited number of regenerators are placed at a selected set of nodes. As OEO regenerators are expensive, the problem of regenerator site selection is of paramount importance in the design of cost-efficient translucent optical networks. In this paper we discuss the practical and deployment issues and metrics that need to be considered in regenerator site selection/placement algorithms and control plane issues in the operation of translucent optical networks. We feel that unless the practical issues are considered by the algorithms and appropriate extensions to control plane protocols are developed and standardized, it is difficult to realize dynamically reconfigurable translucent optical networks.

Impairment aware networking and relevant resiliency issues in all-optical networks

The issues and challenges associated with network planning and engineering of a dynamically reconfigurable all-optical network will be discussed. Possible solutions will be outlined and the effectiveness of some proposed solutions will be demonstrated.

Dynamic establishment of differentiated survivable lightpaths in WDM mesh networks

In the emerging next-generation transport networks, called intelligent optical transport networks, DWDM-based optical components like add-drop multiplexers and optical cross connects will have full knowledge of the wavelengths in the network, status, and traffic carrying capacity of each wavelength. With such intelligence, these intelligent optical networks could create self-connecting and self-regulating connections on-the-fly. Because these networks carry huge volume of traffic, maintaining a high level of service availability at an acceptable level of overhead is an important and critical issue. It is essential to incorporate fault-tolerance into QoS requirements. Since the delay (response time) becomes unbounded as the load approaches the link capacity, delay is usually dominated by the most heavily loaded links; therefore algorithms must attempt to minimize the delay. In this paper, we take fault-tolerance, delay, bandwidth, and availability as QoS parameters to provide varying classes of services based on the type of primary and backup lightpaths and the number of backup lightpaths for studying the problem of dynamically establishing lightpaths in WDM optical networks. The type of primary and backup lightpaths determines the QoS parameters such as response time and bandwidth. Whereas, the number of backup lightpaths determines the level of fault-tolerance and availability of the connection. Based on the service classes, any connection in the network falls into one of the seven classes, viz. single dedicated primary and single dedicated backup, single dedicated primary and multiple dedicated backups, single dedicated primary and single shared backup, single shared primary and single shared backup, single shared primary and multiple shared backup, single dedicated multi-hop primary and single dedicated multi-hop backup, and single shared multi-hop primary and single shared multi-hop backup. We conduct extensive simulation experiments to compare and evaluate the effectiveness of different classes for varying network configurations-varying number of fibers, wavelengths on physical links, and different traffic patterns.