An ant-based algorithm for distributed routing and wavelength assignment in dynamic optical networks

Future optical communication networks are expected to change radically during the next decade. To meet the demanded bandwidth requirements, more dynamism, scalability and automatism will need to be provided. This will also require addressing issues such as the design of highly distributed control plane systems and their associated algorithms to respond to network changes very rapidly. In this work, we propose the use of an ant colony optimization (ACO) algorithm to solve the intrinsic problem of the routing and wavelength assignment (RWA) on wavelength continuity constraint optical networks. The main advantage of the protocol is its distributed nature, which provides higher survivability to network failures or traffic congestion. The protocol has been applied to a specific type of future optical network based on the optical switching of bursts. It has been evaluated through extensive simulations with very promising results, particularly on highly congested scenarios where the load balancing capabilities of the protocol become especially efficient. Results on a partially meshed network like NSFNET show that the ant-based protocol outperforms other RWA algorithms under test in terms of blocking probability without worsening other metrics such as mean route length.Peer ReviewedPostprint (published version

QoS multicast tree construction in IP/DWDM optical internet by bio-inspired algorithms

Copyright @ Elsevier Ltd. All rights reserved.In this paper, two bio-inspired Quality of Service (QoS) multicast algorithms are proposed in IP over dense wavelength division multiplexing (DWDM) optical Internet. Given a QoS multicast request and the delay interval required by the application, both algorithms are able to find a flexible QoS-based cost suboptimal routing tree. They first construct the multicast trees based on ant colony optimization and artificial immune algorithm, respectively. Then a dedicated wavelength assignment algorithm is proposed to assign wavelengths to the trees aiming to minimize the delay of the wavelength conversion. In both algorithms, multicast routing and wavelength assignment are integrated into a single process. Therefore, they can find the multicast trees on which the least wavelength conversion delay is achieved. Load balance is also considered in both algorithms. Simulation results show that these two bio-inspired algorithms can construct high performance QoS routing trees for multicast applications in IP/DWDM optical Internet.This work was supported in part ny the Program for New Century Excellent Talents in University, the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/1, the National Natural Science Foundation of China under Grant no. 60673159 and 70671020, the National High-Tech Reasearch and Development Plan of China under Grant no. 2007AA041201, and the Specialized Research Fund for the Doctoral Program of Higher Education under Grant no. 20070145017

Ant Colony Optimization For Survivable Virtual Topology Mapping In Optical Wdm Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2009Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2009İnternet kullanımının her geçen gün biraz daha yaygınlaşması, bant genişliği problemini de beraberinde getirmiştir. Bu ihtiyacı karşılamak amacıyla, optik ağlarda WDM (dalga boyu bölmeli çoğullama – wavelength division multiplexing) teknolojisi kullanılarak fiber kabloların kapasitesi, her biri farklı dalga boyunda çalışan yüzlerce farklı iletim kanalına bölünmüştür. Paket iletimi yapan üst katmanların kullanacağı uçtan uca kurulan optik bağlantılara ışıkyolu denir. Ağda kurulan tüm ışıkyolları ağın sanal topolojisini oluşturur. Bir fiber üzerinde farklı dalga boylarında olmak koşuluyla birden fazla ışıkyolu yönlendirilebilir. Fakat bir fiberin herhangi bir şekilde hasara uğraması, üzerinden geçen bütün ışıkyollarının kopması sonucu ciddi boyutlarda veri kaybına neden olur. Bu durumdan korunma yöntemlerinden biri ışıkyollarının fiberler üzerinde hataya bağışık şekilde yönlendirilmesidir öyle ki fiziksel katmanda bir ya da daha fazla bağlantı koptuğunda sanal topoloji hala bağlı kalmalıdır. Bu çalışmanın amacı altı farklı karınca koloni algoritması kullanılarak fiberlerin kapasite kısıtlarını aşmadan ve ağ kaynaklarının kullanımını minimize edecek şekilde ışıkyollarını hataya bağışık olarak fiziksel topoloji üzerinde yönlendirmek ve algoritmaları başarım, hız ve ağ kaynaklarının etkin kullanımı açısından karşılaştırmaktır.As the internet use increases significantly in everyday life, the need for bandwidth increases accordingly. To meet this need, high capacity of fibers used in optical networks, can be divided into many channels, using the WDM technology. End-to-end optical connections that the packet layer (IP, Ethernet, etc.) uses are called lightpaths. All the lightpaths set up on the network form the virtual topology. A fiber is able to route more than one ligthpaths with different wavelengths. Any damage to a fiber causes all the channels routed through this link to be broken, which may result in a serious amount of data loss. As a solution to this problem, the virtual layer can be mapped onto the physical topology, such that, a failure on any physical link does not disconnect the virtual topology. This is known as the survivable virtual topology mapping problem. In this study, our aim is to compare the performance of six different ant colony algorithms in finding a survivable mapping of a given virtual topology while minimizing the used wavelength links and without violating the wavelength capacity of fibers in terms of success rates, speed and resource usage.Yüksek LisansM.Sc

Survivable virtual topology design in optical WDM networks using nature-inspired algorithms

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Bilişim Enstitüsü, 2012Thesis (PhD) -- İstanbul Technical University, Institute of Informatics, 2012Günümüzde bilgisayar ağları hayatımızın önemli bir parçası ve ihtiyaç haline gelmiştir. İstediğimiz veriye, istediğimiz anda, daha hızlı, daha güvenli ve kesintisiz olarak erişme isteğimiz aslında ağ altyapısının nasıl tasarlanacağını belirlemektedir. Kullanıcıların istekleri sürekli artarken, teknolojik gelişmelerle birlikte yeni yöntem ve algoritmalarla bu istekleri karşılamanın yolları aranmaktadır. Ağdaki aktarım hızı, aktarım ortamından doğrudan etkilenmektedir; bugün uzak mesafelere en yüksek kapasiteli ve hızlı aktarımın yapılabileceği ortam ise fiberdir. Fiber optik ağlar, fiberin üstün özelliklerini (hız, düşük bit hata oranı, elektromanyetik ortamlardan etkilenmeme, düşük işaret zayıflaması, fiziksel dayanıklılık, ucuzluk, güvenlilik, vs.) en iyi kullanacak şekilde tasarlanan ağlardır. Günümüzde dünyadaki iletişim ağ altyapısı, omurga ağlardan erişim ağlarına kadar, hızla fiber optik ağlara dönüşmektedir. Optik ağların en önemli özelliklerinden biri veri aktarım hızıdır, tek bir fiberden teorik olarak 50 Tb/s veri aktarımı yapılabileceği hesaplanmaktadır. Bugün, lider iletişim firmaları 100 Gb/s ya da 1 Tb/s hızda veri aktarımı yapacak kanalllardan bahsedebiliyorsa, bu, fiziksel altyapı optik bir omurgadan oluştuğu içindir. Dalgaboyu bölmeli çoğullama (WDM) teknolojisi sayesinde bir fiber üzerinde aynı anda kurulabilecek kanal sayısı, günümüz teknolojisiyle yüzler mertebesine çıkabilmektedir. Dalgaboyu bölmeli çoğullama teknolojisi ile, optik aktarım birbiriyle çakışmayan dalgaboyu bantlarına bölünür ve her bir dalgaboyu istenen hızda çalışan, ışıkyolu olarak adlandırılan, bir iletişim kanalını destekler. Böylece, yakın gelecek için öngörülen çok yüksek hızlara çıkmadan bile, bir fiberden herbiri birkaç on Gb/s hızda çalışan yüz dolayında ışıkyolu geçebilmektedir. Bu kadar yüksek hızlarda veri aktarımı, özellikle her bir fiberinde çok sayıda kanalın taşındığı omurga ağlarda bir konuya büyük önem kazandırmaktadır: Hataya bağışıklık. En sık rastlanan hata olan, bir fiberin, herhangi bir nedenle kesilmesi (çoğunlukla inşaat makineleri tarafından, ya da doğal afetlerce), fiber tamir edilene kadar, her saniyede birkaç terabitlik veri kaybı anlamına gelecektir. Örnek olarak 10 km uzunlukta bir fiberin kopma sıklığı 11 yılda birdir. Omurga ağlarda yüzlerce, bazen binlerce, kilometrelik fiberler döşendiği gözönüne alındığında, böyle bir hata durumu için tedbir alınmaması düşünülemez. Optik ağ üzerindeki herhangi bir fibere zarar gelmesi demek bu fiber üzerinden yönlendirilmiş olan tüm ışıkyollarının kopması demektir. Her bir ışıkyolu üzerinden yüksek miktarda (40 Gb/s) veri aktarımı yapıldığından, böyle bir zarar ciddi veri kayıplarına neden olabilir. Temel olarak fiber kopmasına karşı geliştirilen iki yaklaşım vardır. Birinci yaklaşımda fiber üzerinden geçen her bir bağlantının, yani ışıkyolunun, yedek yollarla korunmasıdır. İkinci yaklaşım ise, özellikle birçok internet uygulamasına da uygun ve yeterli olacak şekilde, ışıkyollarının oluşturduğu sanal topolojinin bağlı kalmasının sağlanmasıdır. Bu ikinci yaklaşımda herbir ışıkyoluna ayrı ayrı yedek koruma yollarının atanması yerine, sanal topolojinin korunması dikkate alınarak, üst katmanların (paket katmanları) koruma mekanizmalarının devreye girebilmesi için gereken minimum koşulların sağlanması amaçlanmaktadır. Birinci yaklaşım belirli düzeylerde garantili bir koruma sağlarken yüksek miktarda ağ kaynağının atıl durmasına neden olmakta, dolayısıyla bu kadar üst düzey koruma gerektirmeyen uygulamalar için pahalı bir çözüm sunmaktadır. Son yıllarda özellikle dikkat çeken ikinci yaklaşım ise, daha ekonomik bir yöntemle iletişimin kopmaması garantisini vermekte, ancak daha yavaş bir düzeltme sağlamaktadır. Günümüzde birçok uygulama bağlantı kopmadığı sürece paket katmanının, yeni yol bulma gibi hata düzeltme mekanizmalarının devreye girmesi için gerekli olan, dakikalar mertebesindeki gecikmelere toleranslıdır (web dolaşımı, dosya aktarımı, mesajlaşma, uzaktan erişim gibi). Bu yaklaşım ilkine göre daha az ağ kaynağının atıl kalmasına neden olarak kullanıcıya daha ekonomik hizmet verilmesini sağlayacaktır. Bu çalışmada üzerinde durduğumuz hataya bağışık sanal topoloji tasarımı problemi de bu ikinci yaklaşımı benimsemektedir. Hataya bağışık sanal topoloji tasarımı problemi kendi içinde dört alt probleme ayrılmaktadır: ışıkyollarının belirlenmesi (sanal topolojiyi oluşturma), bu ışıkyollarının herhangi bir fiber kopması durumunda bile sanal topolojinin bağlı kalmasını sağlayacak sekilde fiziksel topoloji üzerinde yönlendirilmesi, dalgaboyu atanması, ve paket trafiğinin yönlendirilmesi. Bu alt problemler ayrı ayrı çözülebilir. Ancak, bunlar bağımsız problemler değildir ve bunları tek tek çözmek elde edilen çözümün kalitesinin çok düşük olmasına neden olabilir. Bununla birlikte, hataya bağışık sanal topoloji tasarımı problemi NP-karmaşıktır. Karmaşıklığı nedeniyle bu problemin, gerçek boyutlu ağlar için, klasik optimizasyon teknikleriyle kabul edilebilir zamanda çözülmesi mümkün değildir. Bu çalışmada, fiziksel topolojinin ve düğümler arası paket trafiği yoğunluğunun bilindiği durumlar için, hataya bağışık sanal topoloji tasarımı problemi bütün halinde ele alınmaktadır. Tezin ilk aşamasında, hataya bağışık sanal topoloji tasarımı probleminin alt problemi olan hataya bağışık sanal topoloji yönlendirmesi problemi ele alınmıştır. Verilen bir sanal topoloji için en az kaynak kullanarak hataya bağışık yönlendirme yapmak için iki farklı doğa-esinli algoritma önerilmektedir: evrimsel algoritmalar ve karınca kolonisi optimizasyonu. Öncelikle önerilen algoritmaların problem için uygun parametre kümesi belirlenmiş, daha sonra, algoritmaların başarımını ölçmek için, deneysel sonuçlar tamsayı doğrusal programlama (ILP) ile elde edilen sonuçlarla karşılaştırılmışır. Sonuçlar göstermektedir ki; önerdiğimiz iki algoritma da, tamsayı doğrusal programlama ile uygun bir çözüm bulunamayan büyük ölçekli ağlar için dahi, problemi çözebilmektedir. Bunun yanında, doğa-esinli algoritmalar çok daha az CPU zamanı ve hafıza kullanmaktadır. Elde edilen çözüm kalitesi ve çözüm için kullanılan CPU zamanının kabul edilebilir düzeyde olması, her iki doğa-esinli algoritmanın da gerçek boyutlu ağlar için kullanılabileceğini doğrulamaktadır. İkinci aşamada, hataya bağışık sanal topoloji tasarımı problemini bir bütün halinde çözmek için dört farklı üst-sezgisel yöntem önerilmektedir. Önerilen üst-sezgisel yöntemler alt seviyedeki sezgiselleri seçme asamasında dört farklı yöntem kullanmaktadır: evrimsel algoritmalar, benzetimli tavlama, karınca kolonisi optimizasyonu ve uyarlamalı yinelenen yapıcı arama. Deneysel sonuçlar tüm üst-sezgisel yöntemlerin hataya bağışık sanal topoloji tasarımı problemini çözmede başarılı olduğunu göstermektedir. Ancak, karınca kolonisi optimizasyonu tabanlı üst-sezgisel diğerlerine göre daha üstün sonuçlar vermektedir. Işıkyolları üzerindeki trafik akışını dengelemek için, karınca kolonisi optimizasyonu tabanlı üst-sezgisele akış deviasyonu yöntemi de eklenmiştir. Literatürde hataya bağışık sanal topoloji tasarımı problemini ele alan tüm çalışmalar çift fiber kopması durumunu gözardı etmektedir. Bu çalışmada, önerdiğimiz üst-sezgisel yöntemin başarımını hem tek hem de çift fiber kopması durumları için değerlendirdik. Önerdiğimiz yöntem çoklu fiber kopması durumları için çok kolay şekilde adapte edilebilmektedir. Tek yapılması gereken hataya bağışıklık kontrolünü yapan yordamın değiştirilmesidir. Deneysel sonuçlar göstermiştir ki, önerdiğimiz karınca kolonisi optimizasyonu tabanlı üst-sezgisel hataya bağışık sanal topoloji tasarımı problemini hem tek hem de çift fiber kopması durumları için kabul edilebilir bir sürede çözebilmektedir. Üst-sezgisel yöntemlerin hataya bağışık sanal topoloji tasarımı çözmedeki başarımını değerlendirebilmek amacıyla, karınca kolonisi optimizasyonu tabanlı üst-sezgiselle elde edilen sonuçlar, literatürde bu problem için önerilmiş başka bir yöntemle karşılaştırılmıştır. Sonuçlar üst-sezgisel yöntemlerin, çok daha az CPU zamanı kullanarak, problem için daha kaliteli çözümler verdiğini göstermektedir.Today, computer networking has become an integral part of our daily life. The steady increase in user demands of high speed and high bandwidth networks causes researchers to seek out new methods and algorithms to meet these demands. The transmission speed in the network is directly affected by the transmission medium. The most effective medium to transmit data is the fiber. Optical networks are designed for the best usage of the superior properties of the fiber, e.g. high speed, high bandwidth, low bit error rate, low attenuation, physical strength, cheapness, etc. The world's communication network infrastructure, from backbone networks to access networks, is consistently turning into optical networks. One of the most important properties of the optical networks is the data transmission rate (up to 50 Tb/s on a single fiber). Today, with the help of the wavelength division multiplexing (WDM) technology, hundreds of channels can be built on a single fiber. WDM is a technology in which the optical transmission is split into a number of non-overlapping wavelength bands, with each wavelength supporting a single communication channel operating at the desired rate. Since multiple WDM channels, also called lightpaths, can coexist on a single fiber, the huge fiber bandwidth can be utilized. Any damage to a physical link (fiber) on the network causes all the lightpaths routed through this link to be broken. Since huge data transmission (40 Gb/s) over each of these lightpaths is possible, such a damage results in a serious amount of data loss. Two different approaches can be used in order to avoid this situation: 1. Survivability on the physical layer, 2. Survivability on the virtual layer. The first approach is the problem of designing a backup link/path for each link/path of the optical layer. The second approach is the problem of designing the optical layer such that the optical layer remains connected in the event of a single or multiple link failure. While the first approach provides faster protection for time-critical applications (such as, IP phone, telemedicine) by reserving more resources, the second approach, i.e. the survivable virtual topology design, which has attracted a lot of attention in recent years, aims to protect connections using less resources. The problem that will be studied in this project is to develop methods for survivable virtual topology design, that enables effective usage of the resources. Survivable virtual topology design consists of four subproblems: determining a set of lightpaths (forming the virtual topology), routing these lightpaths on the physical topology (routing and wavelength assignment (RWA) problem), so that any single fiber cut does not disconnect the virtual topology (survivable virtual topology mapping), assigning wavelengths, and routing the packet traffic. Each of these subproblems can be solved separately. However, they are not independent problems and solving them one by one may degrade the quality of the final result considerably. Furthermore, the survivable virtual topology design is known to be NP-complete. Because of its complexity, it is not possible to solve the problem optimally in an acceptable amount of time using classical optimization techniques, for real-life sized networks. In this thesis, we solve the survivable virtual topology design problem as a whole, where the physical topology and the packet traffic intensities between nodes are given. In the first phase, we propose two different nature inspired heuristics to find a survivable mapping of a given virtual topology with minimum resource usage. Evolutionary algorithms and ant colony optimization algorithms are applied to the problem. To assess the performance of the proposed algorithms, we compare the experimental results with those obtained through integer linear programming. The results show that both of our algorithms can solve the problem even for large-scale network topologies for which a feasible solution cannot be found using integer linear programming. Moreover, the CPU time and the memory used by the nature inspired heuristics is much lower. In the second phase, we propose four different hyper-heuristic approaches to solve the survivable virtual topology design problem as a whole. Each hyper-heuristic approach is based on a different category of nature inspired heuristics: evolutionary algorithms, ant colony optimization, simulated annealing, and adaptive iterated constructive search. Experimental results show that, all proposed hyper-heuristic approaches are successful in designing survivable virtual topologies. Furthermore, the ant colony optimization based hyper-heuristic outperforms the others. To balance the traffic flow over lightpaths, we adapt a flow-deviation method to the ant colony optimization based hyper-heuristic approach. We explore the performance of our hyper-heuristic approach for both single and double-link failures. The proposed approach can be applied to the multiple-link failure problem instances by only changing the survivability control routine. The experimental results show that our approach can solve the problem for both single-link and double-link failures in a reasonable amount of time. To evaluate the quality of the HH approach solutions, we compare these results with the results obtained using tabu search approach. The results show that HH approach outperforms tabu search approach both in solution quality and CPU time.DoktoraPh

Particle swarm optimization for routing and wavelength assignment in next generation WDM networks.

PhDAll-optical Wave Division Multiplexed (WDM) networking is a promising technology for long-haul backbone and large metropolitan optical networks in order to meet the non-diminishing bandwidth demands of future applications and services. Examples could include archival and recovery of data to/from Storage Area Networks (i.e. for banks), High bandwidth medical imaging (for remote operations), High Definition (HD) digital broadcast and streaming over the Internet, distributed orchestrated computing, and peak-demand short-term connectivity for Access Network providers and wireless network operators for backhaul surges. One desirable feature is fast and automatic provisioning. Connection (lightpath) provisioning in optically switched networks requires both route computation and a single wavelength to be assigned for the lightpath. This is called Routing and Wavelength Assignment (RWA). RWA can be classified as static RWA and dynamic RWA. Static RWA is an NP-hard (non-polynomial time hard) optimisation task. Dynamic RWA is even more challenging as connection requests arrive dynamically, on-the-fly and have random connection holding times. Traditionally, global-optimum mathematical search schemes like integer linear programming and graph colouring are used to find an optimal solution for NP-hard problems. However such schemes become unusable for connection provisioning in a dynamic environment, due to the computational complexity and time required to undertake the search. To perform dynamic provisioning, different heuristic and stochastic techniques are used. Particle Swarm Optimisation (PSO) is a population-based global optimisation scheme that belongs to the class of evolutionary search algorithms and has successfully been used to solve many NP-hard optimisation problems in both static and dynamic environments. In this thesis, a novel PSO based scheme is proposed to solve the static RWA case, which can achieve optimal/near-optimal solution. In order to reduce the risk of premature convergence of the swarm and to avoid selecting local optima, a search scheme is proposed to solve the static RWA, based on the position of swarm‘s global best particle and personal best position of each particle. To solve dynamic RWA problem, a PSO based scheme is proposed which can provision a connection within a fraction of a second. This feature is crucial to provisioning services like bandwidth on demand connectivity. To improve the convergence speed of the swarm towards an optimal/near-optimal solution, a novel chaotic factor is introduced into the PSO algorithm, i.e. CPSO, which helps the swarm reach a relatively good solution in fewer iterations. Experimental results for PSO/CPSO based dynamic RWA algorithms show that the proposed schemes perform better compared to other evolutionary techniques like genetic algorithms, ant colony optimization. This is both in terms of quality of solution and computation time. The proposed schemes also show significant improvements in blocking probability performance compared to traditional dynamic RWA schemes like SP-FF and SP-MU algorithms

Distributed Resources Assignment for Optical Burst Switching without Wavelength Conversion (Invited Paper)

The amount of bursty Internet traffic leads to develop new architectures and technologies, such as Optical Burst Switching (OBS), to efficiently satisfy future bandwidth requirements. Burst loss probability is an important quality of service metric for OBS due to its bufferless characteristic, even more critical without wavelengths converters. So, resource assignment is an important issue to solve in OBS networks. In this paper, two distributed resources assignment schemes without wavelength conversion capability are proposed. Whereas the first one is applied at the edge nodes to achieve a loss-free core network, the second is an enhanced routing and wavelength assignment scheme applied at core nodes. Simulation results indicate that the first scheme offers a loss-free solution with blocking probability only at ingress nodes and high traffic load. The second one reduces the network-wide burst loss probability significantly compared with other schemes.Postprint (published version

Cross-layer modeling and optimization of next-generation internet networks

Scaling traditional telecommunication networks so that they are able to cope with the volume of future traffic demands and the stringent European Commission (EC) regulations on emissions would entail unaffordable investments. For this very reason, the design of an innovative ultra-high bandwidth power-efficient network architecture is nowadays a bold topic within the research community. So far, the independent evolution of network layers has resulted in isolated, and hence, far-from-optimal contributions, which have eventually led to the issues today's networks are facing such as inefficient energy strategy, limited network scalability and flexibility, reduced network manageability and increased overall network and customer services costs. Consequently, there is currently large consensus among network operators and the research community that cross-layer interaction and coordination is fundamental for the proper architectural design of next-generation Internet networks. This thesis actively contributes to the this goal by addressing the modeling, optimization and performance analysis of a set of potential technologies to be deployed in future cross-layer network architectures. By applying a transversal design approach (i.e., joint consideration of several network layers), we aim for achieving the maximization of the integration of the different network layers involved in each specific problem. To this end, Part I provides a comprehensive evaluation of optical transport networks (OTNs) based on layer 2 (L2) sub-wavelength switching (SWS) technologies, also taking into consideration the impact of physical layer impairments (PLIs) (L0 phenomena). Indeed, the recent and relevant advances in optical technologies have dramatically increased the impact that PLIs have on the optical signal quality, particularly in the context of SWS networks. Then, in Part II of the thesis, we present a set of case studies where it is shown that the application of operations research (OR) methodologies in the desing/planning stage of future cross-layer Internet network architectures leads to the successful joint optimization of key network performance indicators (KPIs) such as cost (i.e., CAPEX/OPEX), resources usage and energy consumption. OR can definitely play an important role by allowing network designers/architects to obtain good near-optimal solutions to real-sized problems within practical running times

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

Producción CientíficaWe 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.Ministerio de Ciencia e Innovación (Projects TEC2010-21178-C02-02 and TEC2014-53071-C3-2-P)European Community’s Seventh Framework Programme [FP7/2007-2013] CHRON project (Cognitive Heterogeneous Reconfigurable Optical Network) under grant agreement no 25864

Architectures and protocols for sub-wavelength optical networks: contributions to connectionless and connection-oriented data transport

La ràpida evolució d’Internet i l’àmplia gamma de noves aplicacions (per exemple, multimèdia, videoconferència, jocs en línia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A més, algunes d’aquestes aplicacions demanden grans quantitats de recursos d’ample de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexació per divisió de longitud d’ona (WDM) en els anys noranta va fer molt rendible la disponibilitat d’ample de banda. Avui dia, les tecnologies de commutació òptica de circuits són predominants en el nucli de la xarxa, les quals permeten la configuració de canals (lightpaths) a través de la xarxa. No obstant això, la granularitat d’aquests canals ocupa tota la longitud d’ona, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d’ona). Segons la comunitat científica, és necessari augmentar la transparència dels protocols, així com millorar l’aprovisionament d’ample de banda de forma dinàmica. Per tal de fer això realitat, és necessari desenvolupar noves arquitectures. La commutació òptica de ràfegues i de paquets (OBS/OPS), són dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d’ona. En primer lloc, aprofundim en la naturalesa sense connexió en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a ràfega. A més, les col·lisions entre ràfegues degraden el rendiment de la xarxa fins i tot a càrregues molt baixes. Per fer front a aquestes col·lisions, es proposa un esquema de resolució de col·lisions pro actiu basat en un algorisme d’encaminament i assignació de longitud d’ona (RWA) que balanceja de forma automàtica i distribuïda la càrrega en la xarxa. En aquest protocol, el RWA i la transmissió de ràfegues es basen en l’explotació i exploració de regles de commutació que incorporen informació sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s’utilitzen dos tipus de paquets de control per a l’encaminament de les ràfegues i l’actualització de les regles de commutació, respectivament. Per analitzar els beneficis del nou algorisme, s’utilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el mètode proposat millora en diferents marges la resta d’algorismes RWA en funció de la topologia i sense penalitzar altres paràmetres com el retard extrem a extrem. La segona contribució proposa una arquitectura híbrida sense i orientada a connexió sobre la base d’un protocol de control d’accés al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos mètodes d’accés: arbitratge de cua (QA) per a la transmissió de ràfegues sense connexió, i pre-arbitratge (PA) per serveis TDM orientats a connexió. Aquesta arquitectura permet una àmplia gamma d’aplicacions sensibles al retard i al bloqueig. Els resultats avaluats a través de simulacions mostren que en l’accés QA, les ràfegues de més alta prioritat tenen garantides zero pèrdues i latències d’accés molt baixes. Pel que fa a l’accés PA, es reporta que la duplicació de la càrrega TDM augmenta en més d’un ordre la probabilitat de bloqueig, però sense afectar en la mateixa mesura les ràfegues sense connexió. En aquest capítol també es tracten dos dels problemes relacionats amb l’arquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matemàtic per aproximar el retard d’accés inferior i superior com a conseqüència de l’accés QA. En segon lloc, es formula matemàticament la generació i optimització de les topologies virtuals que suporten el protocol per a l’escenari amb tràfic estàtic. Finalment, l’última contribució explora els beneficis d’una arquitectura de xarxa òptica per temps compartit (TSON) basada en elements de càlcul de camins (PCE) centralitzats per tal d’evitar col·lisions en la xarxa. Aquesta arquitectura permet garantir l’aprovisionament orientat a connexió de canals sub-longitud d’ona. En aquest capítol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa depèn en gran mesura de l’assignació i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d’assignació de ranures temporals i es comparen amb les corresponents formulacions de programació lineal (ILP) per al cas estàtic. Per al cas de tràfic dinàmic, proposem i avaluem mitjançant simulació diferents heurístiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freqüencial a l’hora d’assignar les ranures temporals.The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.) is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented amounts of bandwidth resources with diverse quality of service (QoS). The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth. Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network. However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical burst/packet switching (OBS/OPS) are two such proposed technologies under investigation. This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them, we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment (RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology without penalizing other parameters such as end-to-end delay. The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control (MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation. Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.Postprint (published version

Upper Bound Analysis and Routing in Optical Benes Networks

Multistage Interconnection Networks (MIN) are popular in switching and communication applications. It has been used in telecommunication and parallel computing systems for many years. The new challenge facing optical MIN is crosstalk, which is caused by coupling two signals within a switching element. Crosstalk is not too big an issue in the Electrical Domain, but due to the stringent Bit Error Rate (BER) constraint, it is a big major concern in the Optical Domain. In this research dissertation, we will study the blocking probability in the optical network and we will study the deterministic conditions for strictly non-blocking Vertical Stacked Optical Benes Networks (VSOBN) with and without worst-case scenarios. We will establish the upper bound on blocking probability of Vertical Stacked Optical Benes Networks with respect to the number of planes used when the non-blocking requirement is not met. We will then study routing in WDM Benes networks and propose a new routing algorithm so that the number of wavelengths can be reduced. Since routing in WDM optical network is an NP-hard problem, many heuristic algorithms are designed by many researchers to perform this routing. We will also develop a genetic algorithm, simulated annealing algorithm and ant colony technique and apply these AI algorithms to route the connections in WDM Benes network