The continuous growth of traffic demand driven by the brisk increase in number of Internet users and emerging online services creates new challenges for communication networks. The latest advances in Wavelength Division Multiplexing (WDM) technology make it possible to build Transparent Optical Networks (TONs) which are expected to be able to satisfy this rapidly growing capacity demand. Moreover, with the ability of TONs to transparently carry the optical signal from source to destination, electronic processing of the tremendous amount of data can be avoided and optical-to-electrical-to-optical (O/E/O) conversion at intermediate nodes can be eliminated. Consequently, transparent WDM networks consume relatively low power, compared to their electronic-based IP network counterpart. Furthermore, TONs bring also additional benefits in terms of bit rate, signal format, and protocol transparency. However, the absence of O/E/O processing at intermediate nodes in TONs has also some drawbacks. Without regeneration, the quality of the optical signal transmitted from a source to a destination might be degraded due to the effect of physical-layer impairments induced by the transmission through optical fibers and network components. For this reason, routing approaches specifically tailored to account for the effect of physical-layer impairments are needed to avoid setting up connections that don’t satisfy required signal quality at the receiver. Transparency also makes TONs highly vulnerable to deliberate physical-layer attacks. Malicious attacking signals can cause a severe impact on the traffic and for this reason proactive mechanisms, e.g., network design strategies, able to limit their effect are required. Finally, even though energy consumption of transparent WDM networks is lower than in the case of networks processing the traffic at the nodes in the electronic domain, they have the potential to consume even less power. This can be accomplished by targeting the inefficiencies of the current provisioning strategies applied in WDM networks. The work in this thesis addresses the three important aspects mentioned above. In particular, this thesis focuses on routing and wavelength assignment (RWA) strategies specifically devised to target: (i) the lightpath transmission quality, (ii) the network security (i.e., in terms of vulnerability to physical-layer attacks), and (iii) the reduction of the network energy consumption. Our contributions are summarized below. A number of Impairment Constraint Based Routing (ICBR) algorithms have been proposed in the literature to consider physical-layer impairments during the connection provisioning phase. Their objective is to prevent the selection of optical connections (referred to as lightpaths) with poor signal quality. These ICBR approaches always assign each connection request the least impaired lightpath and support only a single threshold of transmission quality, used for all connection requests. However, next generation networks are expected to support a variety of services with disparate requirements for transmission quality. To address this issue, in this thesis we propose an ICBR algorithm supporting differentiation of services at the Bit Error Rate (BER) level, referred to as ICBR-Diff. Our approach takes into account the effect of physical-layer impairments during the connection provisioning phase where various BER thresholds are considered for accepting/blocking connection requests, depending on the signal quality requirements of the connection requests. We tested the proposed ICBR-Diff approach in different network scenarios, including also a fiber heterogeneity. It is shown that it can achieve a significant improvement of network performance in terms of connection blocking, compared to previously published non-differentiated RWA and ICBR algorithms.  Another important challenge to be considered in TONs is their vulnerability to physical-layer attacks. Deliberate attacking signals, e.g., high-power jamming, can cause severe service disruption or even service denial, due to their ability to propagate in the network. Detecting and locating the source of such attacks is difficult, since monitoring must be done in the optical domain, and it is also very expensive. Several attack-aware RWA algorithms have been proposed in the literature to proactively reduce the disruption caused by high-power jamming attacks. However, even with attack-aware network planning mechanisms, the uncontrollable propagation of the attack still remains an issue. To address this problem, we propose the use of power equalizers inside the network nodes in order to limit the propagation of high-power jamming attacks. Because of the high cost of such equipment, we develop a series of heuristics (incl. Greedy Randomized Adaptive Search Procedure (GRASP)) aiming at minimizing the number of power equalizers needed to reduce the network attack vulnerability to a desired level by optimizing the location of the equalizers. Our simulation results show that the equalizer placement obtained by the proposed GRASP approach allows for 50% reduction of the sites with the power equalizers while offering the same level of attack propagation limitation as it is possible to achieve with all nodes having this additional equipment installed. In turn, this potentially yields a significant cost saving.    Energy consumption in TONs has been the target of several studies focusing on the energy-aware and survivable network design problem for both dedicated and shared path protection. However, survivability and energy efficiency in a dynamic provisioning scenario has not been addressed. To fill this gap, in this thesis we focus on the power consumption of survivable WDM network with dynamically provisioned 1:1 dedicated path protected connections. We first investigate the potential energy savings that are achievable by setting all unused protection resources into a lower-power, stand-by state (or sleep mode) during normal network operations. It is shown that in this way the network power consumption can be significantly reduced. Thus, to optimize the energy savings, we propose and evaluate a series of energy-efficient strategies, specifically tailored around the sleep mode functionality. The performance evaluation results reveal the existence of a trade-off between energy saving and connection blocking. Nonetheless, they also show that with the right provisioning strategy it is possible to save a considerable amount of energy with a negligible impact on the connection blocking probability. In order to evaluate the performance of our proposed ICBR-Diff and energy-aware RWA algorithms, we develop two custom-made discrete-event simulators. In addition, the Matlab program of GRASP approach for power equalization placement problem is implemented. / <p>QC 20120508</p>

No description available.

Failure Independent Path-Protecting (FIPP) p-Cycles is a recently proposed protection architecture for transport networks that extends the properties of mesh-like efficiency and ring-like speed of span-protecting p-cycles to path protection. FIPP pcycles provide shared end-to-end protection to working paths and exhibit properties of pre-connection, end-node activation and failure independence. In his thesis we advance the state of the art in FIPP p-cycle networking. We first introduce two new methods for FIPP p-cycle network design: FIPP column generation (CG) and FIPP iterative heuristic (IH). This is followed by the introduction of a new method for joint capacity placement design called FIPP disjoint route set (DRS) joint capacity placement (JCP) which is followed by an in-depth investigation on the effects of jointness in FIPP p-cycle designs. Next we introduce a series of comparative case studies involving several pre-connected network survivability architectures in the context of transparent optical networking. These studies include topics of single, dual and node failure restorability, minimum wavelength assignment and transparent reach analysis. The final contribution of this thesis is the investigation of the capital expenditure associated with the implementation of FIPP p-cycle designs using optical transport networking equipment as described in the NOBEL cost model. A new method called FIPP maximize unit path straddlers (MUPS) is introduced as part of this final study in order to utilize the property of same wavelength protection. This new approach is motivated by opportunities for cost reduction discovered in the initial costing exercise of the NOBEL cost model investigation.

This thesis focuses on the survivable routing problem in WDM mesh networks where the objective is to minimize the total number of wavelengths used for establishing working and protection paths in the WDM networks. The past studies for survivable routing suffers from the scalability problem when the number of nodes/links or connection requests grow in the network. In this thesis, a novel path based shared protection framework namely Inter-Group Shared protection (I-GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. Optimization is performed on these PGs such that sharing of protection wavelengths is considered not only inside a PG, but between the PGs. Simulation results show that I-GSP based integer linear programming model, namely, ILP-II solves the networks in a reasonable amount of time for which a regular integer linear programming formulation, namely, ILP-I becomes computationally intractable. For most of the cases the gap between the optimal solution and the ILP-II ranges between (2-16)%. The proposed ILP-II model yields a scalable solution for the capacity planning in the survivable optical networks based on the proposed I-GSP protection architecture.

This thesis focuses on the survivable routing problem in WDM mesh networks where the objective is to minimize the total number of wavelengths used for establishing working and protection paths in the WDM networks. The past studies for survivable routing suffers from the scalability problem when the number of nodes/links or connection requests grow in the network. In this thesis, a novel path based shared protection framework namely Inter-Group Shared protection (I-GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. Optimization is performed on these PGs such that sharing of protection wavelengths is considered not only inside a PG, but between the PGs. Simulation results show that I-GSP based integer linear programming model, namely, ILP-II solves the networks in a reasonable amount of time for which a regular integer linear programming formulation, namely, ILP-I becomes computationally intractable. For most of the cases the gap between the optimal solution and the ILP-II ranges between (2-16)%. The proposed ILP-II model yields a scalable solution for the capacity planning in the survivable optical networks based on the proposed I-GSP protection architecture.

Finding an optimal solution to the problem of fast and efficient provisioning of reliable connections and failure recovery in future intelligent optical networks is an ongoing challenge. In this dissertation, we investigate and compare the performance of an adapted shared-path protection algorithm with a more conventional approach; both designed for survivable optical Wavelength Division Multiplexing (WDM) mesh networks. The effect of different classes of service on performance is also investigated. Dedicated path protection is a proactive scheme which reserves spare resources to combat single link failures. Conventional Shared-path Protection (CSP) is desirable due to the efficient utilization of resources which results from the sharing of backup paths. Availability is an important performance assessment factor which measures the probability that a connection is in an operational state at some point in time. It is the instantaneous counterpart of reliability. Therefore, connections that do not meet their availability requirements are considered to be unreliable. Reliability Aware Shared-path Protection (RASP) adopts the advantages of CSP by provisioning reliable connections efficiently, but provides protection for unreliable connections only. With the use of a link disjoint parameter, RASP also permits the routing of partial link disjoint backup paths. A simulation study, which evaluates four performance parameters, is undertaken using a South African mesh network. The parameters that are investigated are: 1. Blocking Probability (BP), which considers the percentage of connection requests that are blocked, 2. Backup Success Ratio (BSR), which considers the number of connections that are successfully provisioned with a backup protection path, 3. Backup Primary Resource Ratio (BPR), which considers the ratio of resources utilized to cater for working traffic to the resources reserved for protection paths and lastly 4. Reliability Satisfaction Ratio (RSR), which evaluates the ratio of provisioned connections that meet their availability requirements to the total number of provisioned connections. Under dynamic traffic conditions with varying network load, simulation results show that RASP can provision reliable connections and satisfy Service Level Agreement (SLA) requirements. A competitive Blocking Probability (BP) and lower Backup Primary Resource Ratio (BPR) signify an improvement in resource utilization efficiency. A higher Backup Success Ratio (BSR) was also achieved under high Quality of Service (QoS) constraints. The significance of different availability requirements is evaluated by creating three categories, high availability, medium availability and low availability. These three categories represent three classes of service, with availability used as the QoS parameter. Within each class, the performance of RASP and CSP is observed and analyzed, using the parameters described above. Results show that both the BP and BPR increase with an increase in the availability requirements. The RSR decreases as the reliability requirements increase and a variation in BSR is also indicated. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted

Wavelength division multiplexed (WDM) optical networks are rapidly becoming the technology of choice in network infrastructure and next-generation Internet architectures. WDM networks have the potential to provide unprecedented bandwidth, reduce processing cost, achieve protocol transparency, and enable efficient failure handling. This dissertation addresses the important issues of improving the performance and enhancing the reliability of WDM networks as well as modeling and evaluating the performance of these networks. Optical wavelength conversion is one of the emerging WDM enabling technologies that can significantly improve bandwidth utilization in optical networks. A new approach for the sparse placement of full wavelength converters based on the concept of the k-Dominating Set (k-DS) of a graph is presented. The k-DS approach is also extended to the case of limited conversion capability using three scalable and cost-effective switch designs: flexible node-sharing, strict node-sharing and static mapping. Compared to full search algorithms previously proposed in the literature, the K-DS approach has better blocking performance, has better time complexity and avoids the local minimum problem. The performance benefit of the K-DS approach is demonstrated by extensive simulation. Fiber delay line (FDL) is another emerging WDM technology that can be used to obtain limited optical buffering capability. A placement algorithm, k-WDS, for the sparse placement of FDLs at a set of selected nodes in Optical Burst Switching (OBS) networks is proposed. The algorithm can handle both uniform and non-uniform traffic patterns. Extensive performance tests have shown that k-WDS provides more efficient placement of optical fiber delay lines than the well-known approach of placing the resources at nodes with the highest experienced burst loss. Performance results that compare the benefit of using FDLs versus using optical wavelength converters (OWCs) are presented. A new algorithm, A-WDS, for the placement of an arbitrary numbers of FDLs and OWCs is introduced and is evaluated under different non-uniform traffic loads. This dissertation also introduces a new cost-effective optical switch design using FDL and a QoS-enhanced JET (just enough time) protocol suitable for optical burst switched WDM networks. The enhanced JET protocol allows classes of traffic to benefit from FDLs and OWCs while minimizing the end-to-end delay for high priority bursts. Performance evaluation models of WDM networks represent an important research area that has received increased attention. A new analytical model that captures link dependencies in all-optical WDM networks under uniform traffic is presented. The model enables the estimation of connection blocking probabilities more accurately than previously possible. The basic formula of the dependency between two links in this model reflects their degree of adjacency, the degree of connectivity of the nodes composing them and their carried traffic. The usefulness of the model is illustrated by applying it to the sparse wavelength converters placement problem in WDM networks. A lightpath containing converters is divided into smaller sub-paths such that each sub-path is a wavelength continuous path and the nodes shared between these sub-paths are full wavelength conversion capable. The blocking probability of the entire path is obtained by computing the blocking probabilities of the individual sub-paths. The analytical-based sparse placement algorithm is validated by comparing it with its simulation-based counterpart using a number of network topologies. Rapid recovery from failure and high levels of reliability are extremely important in WDM networks. A new Fault Tolerant Path Protection scheme, FTPP, for WDM mesh networks based on the alarming state of network nodes and links is introduced. The results of extensive simulation tests show that FTPP outperforms known path protection schemes in terms of loss of service ratio and network throughput. The simulation tests used a wide range of values for the load intensity, the failure arrival rate and the failure holding time. The FTPP scheme is next extended to the differentiated services model and its connection blocking performance is evaluated. Finally, a QoS-enhanced FTPP (QEFTPP) routing and path protection scheme in WDM networks is presented. QEFTPP uses preemption to minimize the connection blocking percentage for high priority traffic. Extensive simulation results have shown that QEFTPP achieves a clear QoS differentiation among the traffic classes and provides a good overall network performance.

En les xarxes IP/MPLS sobre WDM on es transporta gran quantitat d'informacio, la capacitat de garantir que el trafic arriba al node de desti ha esdevingut un problema important, ja que la fallada d'un element de la xarxa pot resultar en una gran quantitat d'informacio perduda. Per garantir que el trafic afectat per una fallada arribi al node desti, s'han definit nous algoritmes d'encaminament que incorporen el coneixement de la proteccio en els dues capes: l'optica (WDM) i la basada en paquets (IP/MPLS). D'aquesta manera s'evita reservar recursos per protegir el trafic a les dues capes. Els nous algoritmes resulten en millor us dels recursos de la xarxa, ofereixen rapid temps de recuperacio, eviten la duplicacio de recursos i disminueixen el numero de conversions del trafic de senyal optica a electrica. / The use of optical technology in core networks combined with IP/Multi-Protocol Label Switching (MPLS) solution has been presented as a suitable choice for the next generation Internet architecture. The integration of both layers is facilitated by the development of Generalized MPLS (GMPLS). In this network architecture, a single fibre failure can result in potentially huge data losses as the effects propagate up and through the network causing disruptions in the service of many applications. This research provides and evaluates new QoSP routing schemes that consider both IP/MPLS and optical network layers to compute the paths and backup paths subject to the QoS requirements of the traffic. Although effort has been devoted in developing multi-layer routing algorithms that consider all switching layers, protection is not considered amongst them. This is considered in this thesis. Where electrical to optical signal conversions have been reduded as well as the avoidance of traffic duplications resulting in better use of the network resources.

Les noves tecnologies a la xarxa ens permeten transportar, cada cop més, grans volums d' informació i trànsit de xarxa amb diferents nivells de prioritat. En aquest escenari, on s'ofereix una millor qualitat de servei, les conseqüències d'una fallada en un enllaç o en un node esdevenen més importants. Multiprotocol Lavel Switching (MPLS), juntament amb l'extensió a MPLS generalitzat (GMPLS), proporcionen mecanismes ràpids de recuperació de fallada establint camins, Label Switch Path (LSPs), redundants per ser utilitzats com a camins alternatius. En cas de fallada podrem utilitzar aquests camins per redireccionar el trànsit. El principal objectiu d'aquesta tesi ha estat millorar alguns dels actuals mecanismes de recuperació de fallades MPLS/GMPLS, amb l'objectiu de suportar els requeriments de protecció dels serveis proporcionats per la nova Internet. Per tal de fer aquesta avaluació s'han tingut en compte alguns paràmetres de qualitat de protecció com els temps de recuperació de fallada, les pèrdues de paquets o el consum de recursos.En aquesta tesi presentem una completa revisió i comparació dels principals mètodes de recuperació de fallada basats en MPLS. Aquest anàlisi inclou els mètodes de protecció del camí (backups globals, backups inversos i protecció 1+1), els mètodes de protecció locals i els mètodes de protecció de segments. També s'ha tingut en compte l'extensió d'aquests mecanismes a les xarxes òptiques mitjançant el pla de control proporcionat per GMPLS.En una primera fase d'aquest treball, cada mètode de recuperació de fallades és analitzat sense tenir en compte restriccions de recursos o de topologia. Aquest anàlisi ens dóna una primera classificació dels millors mecanismes de protecció en termes de pèrdues de paquets i temps de recuperació. Aquest primer anàlisi no és aplicable a xarxes reals. Per tal de tenir en compte aquest nou escenari, en una segona fase, s'analitzen els algorismes d'encaminament on sí tindrem en compte aquestes limitacions i restriccions de la xarxa. Es presenten alguns dels principals algorismes d'encaminament amb qualitat de servei i alguna de les principals propostes d'encaminament per xarxes MPLS. La majoria dels actual algorismes d'encaminament no tenen en compte l'establiment de rutes alternatives o utilitzen els mateixos objectius per seleccionar els camins de treball i els de protecció. Per millorar el nivell de protecció introduïm i formalitzem dos nous conceptes: la Probabilitat de fallada de la xarxa i l'Impacte de fallada. Un anàlisi de la xarxa a nivell físic proporciona un primer element per avaluar el nivell de protecció en termes de fiabilitat i disponibilitat de la xarxa. Formalitzem l'impacte d'una fallada, quant a la degradació de la qualitat de servei (en termes de retard i pèrdues de paquets). Expliquem la nostra proposta per reduir la probabilitat de fallada i l'impacte de fallada. Per últim fem una nova definició i classificació dels serveis de xarxa segons els valors requerits de probabilitat de fallada i impacte.Un dels aspectes que destaquem dels resultats d'aquesta tesi és que els mecanismes de protecció global del camí maximitzen la fiabilitat de la xarxa, mentre que les tècniques de protecció local o de segments de xarxa minimitzen l'impacte de fallada. Per tant podem assolir mínim impacte i màxima fiabilitat aplicant protecció local a tota la xarxa, però no és una proposta escalable en termes de consum de recursos. Nosaltres proposem un mecanisme intermig, aplicant protecció de segments combinat amb el nostre model d'avaluació de la probabilitat de fallada. Resumint, aquesta tesi presenta diversos mecanismes per l'anàlisi del nivell de protecció de la xarxa. Els resultats dels models i mecanismes proposats milloren la fiabilitat i minimitzen l'impacte d'una fallada en la xarxa. / New network technology enables increasingly higher volumes of information to be carried. Various types of mission-critical, higher-priority traffic are now transported over these networks. In this scenario, when offering better quality of service, the consequences of a fault in a link or node become more pronounced. Multiprotocol Label Switching (MPLS) and the extended Generalized MPLS (GMPLS) provide fast mechanisms for recovery from failures by establishing redundant Label Switch Paths as backup paths. With these backups, traffic can always be redirected in case of failure. The main objective of this thesis is to improve some of the current MPLS/GMPLS fault recovery methods, in order to support the protection requirements of the new Internet services. Some parameters, such as fault recovery time, packet loss or resource consumption, all within the scope of this quality of protection, are considered. In this thesis a review and detailed comparison of the MPLS fault recovery methods are presented. Path protection methods (global backups, reverse backups and 1+1 methods), as well as segment protection and local methods are included in this analysis. The extension of these mechanisms to optical networks using GMPLS control plane is also taken into account.In the first phase MPLS fault recovery methods are analyzed without taking into account resource or network topology constraints. This analysis reported a first classification of the best protection methods in terms of packet loss and recovery time. This first analysis cannot be applied to real networks. In real networks, bandwidth or network topology constraints can force a change in the a priori optimal protection choice. In this new scenario, current routing algorithms must be analyzed. The main aspects of the QoS routing methods are introduced, and some of these mechanisms are described and compared. QoS routing algorithms do not include protection as a main objective and, moreover, the same QoS objectives for selecting the working path are used for selecting the backup path. In order to evaluate the quality of protection, two novel concepts are introduced and analyzed: the network failure probability and the failure impact. The physical network provides an initial value of the network protection level in terms of network reliability and availability. A proposal to evaluate network reliability is introduced, and a formulation to calculate the failure impact (the QoS degradation in terms of packet loss and delay) is presented. A proposal to reduce the failure probability and failure impact as well as the enhancement of some current routing algorithms in order to achieve better protection are explained. A review of the traffic services protection requirements and a new classification, based on the failure probability and failure impact values, is also provided in this work.Results show that path protection schemes improve network reliability. Segment/local protection schemes reduce the network failure impact. Minimum impact with maximum reliability can be achieved using local protection throughout the entire network. However, it is not scalable in terms of resource consumption. In this case our failure probability evaluation model can be used to minimize the required resources. Results demonstrate the reduction of the failure impact combining segment protection and our network reliability evaluation model in different network scenarios.In summary, an in-depth analysis is carried out and a formulation to evaluate the network protection level is presented. This evaluation is based on network reliability maximization and failure impact reduction in terms of QoS degradation. A scalable proposal in terms of resource consumption, detailed and experimentally analyzed, offers the required level of protection in different network scenarios for different traffic services.

Optical WDM network is the suitable transport mechanism for ever increasing bandwidth intensive internet applications. The WDM technique transmits the data over several different wavelengths simultaneously through an opticalfiber and the switching is done at wavelength level. The connection between the source and destination is called the light path. Since the WDM network carries huge amount of tra c, any failure can cause massive data loss. Therefore protecting the network against failure is an important issue. Maintaining high level of service availability is an important aspect of service provider. To provide cost effective service, all-optical network is the suitable choice for the service provider. But in all optical network, the signals are forced to remain in optical domain from source to destination. In the firrst part of the thesis, we deal the physical layer impairments (PLIs) aware shared-path provisioning on a wavelength routed all-optical networks. As the signal travels longer distances, the quality of the signal gets degraded and the receiver may not be able to detect the optical signal properly. Our objective is to establish a light path for both the working path and protection path with acceptable signal quality at the receiver. We propose an impairment aware integer linear programming (ILP) and impairment aware heuristic algorithm that takes into account the PLIs. The ILP provides the optimal solution. It is solved using IBM ILOG CPLEX solver. It is intractable for large size net-work. Therefore we propose the heuristic algorithm for large size network. It is evaluated through discrete-event simulation. But the algorithm provides only the suboptimal solution. To know the performance of this algorithm, the simulation result is compared with the optimal solution. We compute total blocking probability, restoration delay, computation time, and connection setup delay with respect to network load for the heuristic algorithm. We compare the performance of shared-path protection with dedicated-path protection and evaluate the percentage of resource saving of shared-path protection over the dedicated-path protection. In the second and third part of the thesis, we address the issues related to flexible-grid optical networks. In wavelength routed optical network, the bandwidth of each wavelength is fixed and rigid. It supports coarse grained tra c grooming and leads to ancient spectrum utilization. To overcome this, flexible-grid optical networks are proposed. It supports flexible bandwidth, and ne grained tra c groom In the second part of the thesis, we address the routing and spectrum allocation (RSA) algorithm for variable-bit-rate data tra c for flexible-grid optical networks. The RSA problem is NP-complete. Therefore a two-step heuristic approach (routing and spectrum allocation) is proposed to solve the RSA problem. The first step is solved by using a classical shortest path algorithm. For the second step we propose two heuristic schemes for frequency-slot allocation: (i) largest number of free frequency-slot allocation scheme and (ii) largest number of free frequency-slot maintaining scheme. As the network load increases, the spectrum is highly fragmented. To mitigate the fragmentation of the spectrum, we propose a xed-path least-fragmentation heuristic algorithm which fragments the spectrum minimally. It also supports varying-bit-rate tra c and also supports dynamic arrival connection requests. Through extensive simulations the proposed algorithms have been evaluated. Our simulation results show that the algorithms perform better in terms of spectrum utilization, blocking probability, and fraction of fragmentation of the spectrum. The spectrum utilization can reach up to a maximum of 92% and that only 71% of the spectrum is fragmented under maximum network load condition. Finally in the third part of the thesis, we discuss PLIs-aware RSA for the transparent exible-grid optical network. In this network, not only the optical signal expected to travel longer distance, but also to support higher line rates, i.e., data rate is increased up to 1 Tb/s. In such a high data rate, the optical signals are more prone to impairments and noises. As the transmission distance increases, optical signals are subject to tra-verse over many bandwidth-variable wavelength cross connects (BV-WXC) and multiple fibber spans due to which the PLIs get accumulated and are added to the optical signal. These accumulated impairments degrades the signal quality to an unacceptable level at the receiver, the quality of transmission falls below the acceptable threshold value, and the receiver may not be able to detect the signal properly. Therefore our objective is to develop an impairment aware RSA algorithm which establishes the QoT satisfied empathy based on the available resources and the quality of the signal available at the receiver. We formulate the PLIs-RSA problem as an ILP that provides an optimal solution. The optimal solution is obtained by solving the ILP using IBM ILOG CPLEX optimization solver. Since ILP is not efficient for large-size networks, we propose a heuristic algorithm for such a large-size networks. The signal power is measured at the receiver and the connection is established only when the signal power lies above the threshold value. The heuristic algorithm is evaluated through discrete-event simulation. It gives the sub-optimal solution. The simulation result is compared with optimal solution. The result shows that heuristic algorithm performs closer to the ILP. We compute the total blocking probability versus the network load for different spectrum allocation schemes. Total blocking probability is the sum of frequency-slot blocking probability and QoT blocking probability. We compute spectrum efficiency for the proposed algorithm. We also compare our algorithm with the existing routing and spectrum allocation algorithm, and the result shows that our algorithm outperforms the existing algorithms in terms of blocking probability and spectrum utilization.