Designing Survivable Wavelength Division Multiplexing (WDM) Mesh Networks

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

Novel Approaches and Architecture for Survivable Optical Internet

Any unexpected disruption to WDM (Wavelength Division Multiplexing) based optical networks which carry data traffic at tera-bit per second may result in a huge loss to its end-users and the carrier itself. Thus survivability has been well-recognized as one of the most important objectives in the design of optical Internet. This thesis proposes a novel survivable routing architecture for the optical Internet. We focus on a number of key issues that are essential to achieve the desired service scenarios, including the tasks of (a) minimizing the total number of wavelengths used for establishing working and protection paths in WDM networks; (b) minimizing the number of affected working paths in case of a link failure; (c) handling large scale WDM mesh networks; and (d) supporting both Quality of Service (QoS) and best-effort based working lightpaths. To implement the above objectives, a novel path based shared protection framework namely Group Shared protection (GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy, and optimization is performed on these PGs. To the best of our knowledge this is the first work done in the area of group based WDM survivable routing approaches where not only the resource sharing is conducted among the PGs to achieve the best possible capacity efficiency, but also an integrated survivable routing framework is provided by incorporating the above objectives. Simulation results show the effectiveness of the proposed schemes

Novel Approaches and Architecture for Survivable Optical Internet

Any unexpected disruption to WDM (Wavelength Division Multiplexing) based optical networks which carry data traffic at tera-bit per second may result in a huge loss to its end-users and the carrier itself. Thus survivability has been well-recognized as one of the most important objectives in the design of optical Internet. This thesis proposes a novel survivable routing architecture for the optical Internet. We focus on a number of key issues that are essential to achieve the desired service scenarios, including the tasks of (a) minimizing the total number of wavelengths used for establishing working and protection paths in WDM networks; (b) minimizing the number of affected working paths in case of a link failure; (c) handling large scale WDM mesh networks; and (d) supporting both Quality of Service (QoS) and best-effort based working lightpaths. To implement the above objectives, a novel path based shared protection framework namely Group Shared protection (GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy, and optimization is performed on these PGs. To the best of our knowledge this is the first work done in the area of group based WDM survivable routing approaches where not only the resource sharing is conducted among the PGs to achieve the best possible capacity efficiency, but also an integrated survivable routing framework is provided by incorporating the above objectives. Simulation results show the effectiveness of the proposed schemes

Characterization, design and re-optimization on multi-layer optical networks

L'augment de volum de tràfic IP provocat per l'increment de serveis multimèdia com HDTV o vídeo conferència planteja nous reptes als operadors de xarxa per tal de proveir transmissió de dades eficient. Tot i que les xarxes mallades amb multiplexació per divisió de longitud d'ona (DWDM) suporten connexions òptiques de gran velocitat, aquestes xarxes manquen de flexibilitat per suportar tràfic d’inferior granularitat, fet que provoca un pobre ús d'ample de banda. Per fer front al transport d'aquest tràfic heterogeni, les xarxes multicapa representen la millor solució. Les xarxes òptiques multicapa permeten optimitzar la capacitat mitjançant l'empaquetament de connexions de baixa velocitat dins de connexions òptiques de gran velocitat. Durant aquesta operació, es crea i modifica constantment una topologia virtual dinàmica gràcies al pla de control responsable d’aquestes operacions. Donada aquesta dinamicitat, un ús sub-òptim de recursos pot existir a la xarxa en un moment donat. En aquest context, una re-optimizació periòdica dels recursos utilitzats pot ser aplicada, millorant així l'ús de recursos. Aquesta tesi està dedicada a la caracterització, planificació, i re-optimització de xarxes òptiques multicapa de nova generació des d’un punt de vista unificat incloent optimització als nivells de capa física, capa òptica, capa virtual i pla de control. Concretament s'han desenvolupat models estadístics i de programació matemàtica i meta-heurístiques. Aquest objectiu principal s'ha assolit mitjançant cinc objectius concrets cobrint diversos temes oberts de recerca. En primer lloc, proposem una metodologia estadística per millorar el càlcul del factor Q en problemes d'assignació de ruta i longitud d'ona considerant interaccions físiques (IA-RWA). Amb aquest objectiu, proposem dos models estadístics per computar l'efecte XPM (el coll d'ampolla en termes de computació i complexitat) per problemes IA-RWA, demostrant la precisió d’ambdós models en el càlcul del factor Q en escenaris reals de tràfic. En segon lloc i fixant-nos a la capa òptica, presentem un nou particionament del conjunt de longituds d'ona que permet maximitzar, respecte el cas habitual, la quantitat de tràfic extra proveït en entorns de protecció compartida. Concretament, definim diversos models estadístics per estimar la quantitat de tràfic donat un grau de servei objectiu, i diferents models de planificació de xarxa amb l'objectiu de maximitzar els ingressos previstos i el valor actual net de la xarxa. Després de resoldre aquests problemes per xarxes reals, concloem que la nostra proposta maximitza ambdós objectius. En tercer lloc, afrontem el disseny de xarxes multicapa robustes davant de fallida simple a la capa IP/MPLS i als enllaços de fibra. Per resoldre aquest problema eficientment, proposem un enfocament basat en sobre-dimensionar l'equipament de la capa IP/MPLS i recuperar la connectivitat i el comparem amb la solució convencional basada en duplicar la capa IP/MPLS. Després de comparar solucions mitjançant models ILP i heurístiques, concloem que la nostra solució permet obtenir un estalvi significatiu en termes de costos de desplegament. Com a quart objectiu, introduïm un mecanisme adaptatiu per reduir l'ús de ports opto-electrònics (O/E) en xarxes multicapa sota escenaris de tràfic dinàmic. Una formulació ILP i diverses heurístiques són desenvolupades per resoldre aquest problema, que permet reduir significativament l’ús de ports O/E en temps molt curts. Finalment, adrecem el problema de disseny resilient del pla de control GMPLS. Després de proposar un nou model analític per quantificar la resiliència en topologies mallades de pla de control, usem aquest model per proposar un problema de disseny de pla de control. Proposem un procediment iteratiu lineal i una heurística i els usem per resoldre instàncies reals, arribant a la conclusió que es pot reduir significativament la quantitat d'enllaços del pla de control sense afectar la qualitat de servei a la xarxa.The explosion of IP traffic due to the increase of IP-based multimedia services such as HDTV or video conferencing poses new challenges to network operators to provide a cost-effective data transmission. Although Dense Wavelength Division Multiplexing (DWDM) meshed transport networks support high-speed optical connections, these networks lack the flexibility to support sub-wavelength traffic leading to poor bandwidth usage. To cope with the transport of that huge and heterogeneous amount of traffic, multilayer networks represent the most accepted architectural solution. Multilayer optical networks allow optimizing network capacity by means of packing several low-speed traffic streams into higher-speed optical connections (lightpaths). During this operation, a dynamic virtual topology is created and modified the whole time thanks to a control plane responsible for the establishment, maintenance, and release of connections. Because of this dynamicity, a suboptimal allocation of resources may exist at any time. In this context, a periodically resource reallocation could be deployed in the network, thus improving network resource utilization. This thesis is devoted to the characterization, planning, and re-optimization of next-generation multilayer networks from an integral perspective including physical layer, optical layer, virtual layer, and control plane optimization. To this aim, statistical models, mathematical programming models and meta-heuristics are developed. More specifically, this main objective has been attained by developing five goals covering different open issues. First, we provide a statistical methodology to improve the computation of the Q-factor for impairment-aware routing and wavelength assignment problems (IA-RWA). To this aim we propose two statistical models to compute the Cross-Phase Modulation variance (which represents the bottleneck in terms of computation time and complexity) in off-line and on-line IA-RWA problems, proving the accuracy of both models when computing Q-factor values in real traffic scenarios. Second and moving to the optical layer, we present a new wavelength partitioning scheme that allows maximizing the amount of extra traffic provided in shared path protected environments compared with current solutions. Specifically, we define several statistical models to estimate the traffic intensity given a target grade of service, and different network planning problems for maximizing the expected revenues and net present value. After solving these problems for real networks, we conclude that our proposed scheme maximizes both revenues and NPV. Third, we tackle the design of survivable multilayer networks against single failures at the IP/MPLS layer and WSON links. To efficiently solve this problem, we propose a new approach based on over-dimensioning IP/MPLS devices and lightpath connectivity and recovery and we compare it against the conventional solution based on duplicating backbone IP/MPLS nodes. After evaluating both approaches by means of ILP models and heuristic algorithms, we conclude that our proposed approach leads to significant CAPEX savings. Fourth, we introduce an adaptive mechanism to reduce the usage of opto-electronic (O/E) ports of IP/MPLS-over-WSON multilayer networks in dynamic scenarios. A ILP formulation and several heuristics are developed to solve this problem, which allows significantly reducing the usage of O/E ports in very short running times. Finally, we address the design of resilient control plane topologies in GMPLS-enabled transport networks. After proposing a novel analytical model to quantify the resilience in mesh control plane topologies, we use this model to propose a problem to design the control plane topology. An iterative model and a heuristic are proposed and used to solve real instances, concluding that a significant reduction in the number of control plane links can be performed without affecting the quality of service of the network

Design and operation of mesh-restorable WDM networks

The explosive growth of Web-related services over the Internet is bringing millions of new users online, thus creating a growing demand for bandwidth. Wavelength Division Multiplexed (WDM) networks, employing wavelength routing has emerged as the dominant technology to satisfy this growing demand for bandwidth. As the amount of traffic carried is larger, any single failure can be catastrophic. Survivability becomes indispensable in such networks. Therefore, it is imperative to design networks that can quickly and efficiently recover from failures.;In this dissertation, we explore the design and operation of survivable optical networks. We study several survivability paradigms for surviving single link failures. A restoration model is developed based on a combination of these paradigms. We propose an optimal design and upgrade scheme for WDM backbone networks. We formulate an integer programming-based design problem to minimize the total facility cost. This framework provides a cost effective way of upgrading the network by identifying how much resources to budget at each stage of network evolution. This results in significant cost reductions for the network service provider.;As part of network operation, we capture multiple operational phases in survivable network operation as a single integer programming formulation. This common framework incorporates service disruption and includes a service differentiation model based on lightpath protection. However, the complexity of the optimization problem makes the formulation applicable only for network provisioning and o2ine reconfiguration. The direct use of such methods for online reconfiguration remains limited to small networks with few tens of wavelengths. We develop a heuristic algorithm based on LP relaxation technique for fast, near optimal, online reconfiguration. Since the ILP variables are relaxed, we provide a way to derive a feasible solution from the relaxed problem. Most of the current approaches assume centralized information. They do not scale well as they rely on per-flow information. This motivates the need for developing dynamic algorithms based on partial information. The partial information we use can be easily obtained from traffic engineering extensions to routing protocols. Finally, the performance of partial information routing algorithms is compared through simulation studies

Using GRASP and GA to design resilient and cost-effective IP/MPLS networks

The main objective of this thesis is to find good quality solutions for representative instances of the problem of designing a resilient and low cost IP/MPLS network, to be deployed over an existing optical transport network. This research is motivated by two complementary real-world application cases, which comprise the most important commercial and academic networks of Uruguay. To achieve this goal, we performed an exhaustive analysis of existing models and technologies. From all of them we took elements that were contrasted with the particular requirements of our counterparts. We highlight among these requirements, the need of getting solutions transparently implementable over a heterogeneous network environment, which limit us to use widely standardized features of related technologies. We decided to create new models more suitable to fit these needs. These models are intrinsically hard to solve (NP-Hard). Thus we developed metaheuristic based algorithms to find solutions to these real-world instances. Evolutionary Algorithms and Greedy Randomized Adaptive Search Procedures obtained the best results. As it usually happens, real-world planning problems are surrounded by uncertainty. Therefore, we have worked closely with our counterparts to reduce the fuzziness upon data to a set of representative cases. They were combined with different strategies of design to get to scenarios, which were translated into instances of these problems. Finally, the algorithms were fed with this information, and from their outcome we derived our results and conclusions

Efficient computation and communication management for all-pairs interactions

Big data continues to grow in size for all sciences. New methods like those proposed are needed to further reduce memory footprints and distribute work equally across compute nodes both in local HPC systems and rented cluster resources in the cloud. Modern infrastructures have evolved to support these big data computations and that includes key pieces like our internet backbones and data center networks. Many optical networks face heterogeneous communication requests requiring topologies to be efficient and fault tolerant. The all-pairs problem requires all elements (computation datasets or communication nodes) to be paired with all other elements. These all-pairs problems occur in many research fields and have significant impacts, which has led to their continued interest. We proposed using cyclic quorum sets to efficiently manage all-pairs computations. We proved these sets have an all-pairs property that allows for minimal data replication and for distributed, load balanced, and communication-less computation management. The quorums are $O\left(\frac{N}{\sqrt{P}}\right)$ in size, up to 50% smaller than dual $\frac{N}{\sqrt{P}}$ array implementations, and significantly smaller than solutions requiring all data. Scaling from 16 to 512 cores (1 to 32 compute nodes) and using real dataset inputs, application experiments demonstrated scalability with greater than 150x (super-linear) speedup and less than 1/4th the memory usage per process. Cyclic quorum sets can provided benefits to more than just computations. The sets can also provide a guarantee that all pairs of optical nodes in a network can communicate. Our evaluation analyzed the fault tolerance of routing optical cycles based on cyclic quorum sets. With this method of topology construction, unicast and multicast communication requests do not need to be known or even modeled a priori. In the presence of network single-link faults, our simulated cycle routing had greater than 99% average fault coverage. Hence, even in the presence of a network fault, the optical networks could continue operation of nearly all node pair communications. Lastly, we proposed a generalized $R$ redundant cyclic quorum set. These sets guarantee all pairs of nodes occur at least $R$ times. When applied to routing cycles in optical networks, this technique provided almost fault-tolerant communications. More importantly, when applied using only single cycles rather than the standard paired cycles, the generalized $R$ redundancy technique almost halved the necessary light-trail resources while maintaining the fault tolerance and dependability expected from cycle-based routing. \section*{Problem Description} Big Data in recent years has become a focal point for science and commerce. As datasets grow larger, traditional methods and algorithms are challenged on whether they are able to truly scale. This has led to phrases like, swimming in sensors, drowning in data. Our work addresses some of the challenges facing a particular type of big data interaction. The interaction considered requires all elements in a set to interact with all other elements in the set. The all-pairs interaction is a general computation or communication problem that occurs frequently and can be as simple as considering the shaking of hands by all attendees to a party. More formally there is set $E_N$, where there are $N$ elements indexed $0$ to $\left(N-1\right)$. $$E_N = \left\lbrace e_0, e_1, ... , e_{N-1} \right\rbrace$$ The elements in this general formulation can be simple, single communication node or single item data structures, e.g., $E_N$ could simply be all nodes in a network or be a large array of $N$ values. Or, elements can be complex data structures with many fields / values. Fields are not restricted to a single data type either, as many big data problems can rely on heterogeneous datasets. The all-pairs interaction considers all possible pairs of elements, $\binom{N}{2}$. $$\left\lbrace \left(e_0,e_1\right), \left(e_0,e_2\right), ... , \left(e_0,e_{N-1}\right), \left(e_1,e_2\right), \left(e_1,e_3\right) , ... , \left(e_1, e_{N-1}\right) , ... , \left(e_{N-2},e_{N-1}\right) \right\rbrace$$ While the simple hand shake example could be considered a symmetric interaction. e_i \leftrightarrow e_j , i The all-pairs interaction can be more generally represented by two separate interactions to better represent the computational or communication complexity in those problems where the all-pairs operation is not commutative. \[ e_i \rightarrow e_j, i \[ e_i \leftarrow e_j, i The computational complexity of this general algorithmic form is not daunting. \[\binom{N}{2} = \frac{\left( N-1\right) N}{2} = O\left( N^2\right) In fact, even for pair computations that do not have the commutative property, the complexity is unchanged. In general, polynomial $O\left(N^2\right)$ computations are considered highly computationally scalable. When performing an all-pairs data interaction on the big data scale sizes, while the computational complexity theoretically is manageable, the data management becomes complex. The problem definition inherently requires access to the entire dataset, such that every data element can be paired and processed with every other data element in the set. When the datasets exceed a system\u27s memory size, this presents a challenge, which our methods address. \section*{Solution Approach} For efficiency and distributed control, it is common in distributed systems and algorithms to group nodes into intersecting sets referred to as quorum sets. Our management techniques rely on the established quorum set theories for their efficiencies and management. We then proved an all-pairs property of cyclic quorum sets, which is central to guaranteeing that all-pairs of elements (nodes or data) are able to interact in the system. The all-pairs data computation problem requires all data elements to be paired with all other data elements. These all-pairs problems occur in many science fields, which has led to their continued interest. Our research addresses the memory and computation time challenges of the general all-pairs big data interaction computations through the use of memory efficient computation management techniques. Proposed were methods using distributed computing to share the computational workload. Although the problem definition requires every data element to have access to and interact with the entire dataset, our cyclic quorum set techniques relax this restriction in distributed systems. This computation management is used to reduce memory resource requirements per node and enable big data scalability. Implementation evaluation of a large bioinformatics application demonstrated scalability on real datasets with linear and at times super-linear speedups. Reductions in memory requirements per node allowed for processing larger datasets that would not have been feasible on a single node either due to memory or time requirements. Similar cyclic quorum set techniques were used to address efficient and fault tolerant communication routing challenges in optical networking. Cycle-based optical network routing, whether using SONET rings or p-cycles, provide the sufficient reliability in networks. Light-trails forming a cycle in the network allow broadcasts within a cycle to be used for efficient multicast communications. Using the proven ``all-pairs\u27\u27 property of cyclic quorum sets, we could guarantee all pairs of nodes will occur in one or more quorums, so efficient, arbitrary unicast communication can occur between any two nodes. Efficient broadcasts to all network nodes are possible by a node broadcasting to all quorum cycles to which it belongs ($O\left(\sqrt{N}\right)$.) We analyzed node pair communications in networks, specifically, the fault tolerance aspects of using cyclic quorum sets to route cycles. Observed was better than 99% average single fault coverage and some node pair communications were protected by more than one cycle. Exploiting this redundant node pair protections revealed even greater resource efficiencies. Common cycle routing techniques will use pairs of cycles to achieve both routing and fault-tolerance, which uses substantial resources and creates the potential for underutilization. Instead, when we intentionally designed cyclic quorum sets with $R$ redundant pairs of nodes and utilized the $R$ redundancy within the quorum cycles to replace the pair of cycles with just a single cycle, we saw network resource usage almost halved. Our analysis of several networks showed $R=2$ redundant single cycles had 96.60 - 99.37% single link fault coverage, while reducing resource usage by 42.9 - 47.18% on average. Increasing redundancy to $R=3$ redundant cycles maintained a 93.23 - 99.34% average fault coverage even with two simultaneous link faults and used 38.85 - 42.39% fewer resources on average