by Lee Chi Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 63-65). / Abstracts in English and Chinese. / Chapter CHAPTER 1 --- INTRODUCTION --- p.5 / Chapter 1.1 --- Background --- p.5 / Chapter 1.1.1 --- Backbone network - Long haul mesh network problem --- p.5 / Chapter 1.1.2 --- Access network ´ؤ Last mile problems --- p.8 / Chapter 1.1.3 --- Network integration --- p.9 / Chapter 1.2 --- SUMMARY OF INSIGHTS --- p.10 / Chapter 1.3 --- Contribution of this thesis --- p.11 / Chapter 1.4 --- Structure of the thesis --- p.11 / Chapter CHAPTER 2 --- PREVIOUS PROTECTION ARCHITECTURES --- p.12 / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Traditional physical protection architectures in metro area --- p.13 / Chapter 2.2.1 --- Self healing ring --- p.17 / Chapter 2.2.2 --- Some terminology in ring protection --- p.13 / Chapter 2.2.3 --- Unidirectional path-switched rings (UPSR) [17] --- p.13 / Chapter 2.2.4 --- Bidirectional line-switched rings (BLSR) [17] --- p.14 / Chapter 2.2.5 --- Ring interconnection and dual homing [17] --- p.16 / Chapter 2.3 --- Traditional physical protection architectures in access networks --- p.17 / Chapter 2.3.1 --- Basic architecture in passive optical networks --- p.17 / Chapter 2.3.2 --- Fault management issue in access networks --- p.18 / Chapter 2.3.3 --- Some protection architectures --- p.18 / Chapter 2.4 --- Recent protection architectures on a ccess networks --- p.21 / Chapter 2.4.1 --- Star-Ring-Bus architecture --- p.21 / Chapter 2.5 --- Concluding remarks --- p.22 / Chapter CHAPTER 3 --- GROUP PROTECTION ARCHITECTURE (GPA) FOR TRAFFIC RESTORATION IN MULTI- WAVELENGTH PASSIVE OPTICAL NETWORKS --- p.23 / Chapter 3.1 --- Background --- p.23 / Chapter 3.2 --- Organization of Chapter 3 --- p.24 / Chapter 3.3 --- Overview of Group Protection Architecture --- p.24 / Chapter 3.3.1 --- Network architecture --- p.24 / Chapter 3.3.2 --- Wavelength assignment --- p.25 / Chapter 3.3.3 --- Normal operation of the scheme --- p.25 / Chapter 3.3.4 --- Protection mechanism --- p.26 / Chapter 3.4 --- Enhanced GPA architecture --- p.27 / Chapter 3.4.1 --- Network architecture --- p.27 / Chapter 3.4.2 --- Wavelength assignment --- p.28 / Chapter 3.4.3 --- Realization of network elements --- p.28 / Chapter 3.4.3.1 --- Optical line terminal (OLT) --- p.28 / Chapter 3.4.3.2 --- Remote node (RN) --- p.29 / Chapter 3.4.3.3 --- Realization of optical network unit (ONU) --- p.30 / Chapter 3.4.4 --- Protection switching and restoration --- p.31 / Chapter 3.4.5 --- Experimental demonstration --- p.31 / Chapter 3.5 --- Conclusion --- p.33 / Chapter CHAPTER 4 --- A NOVEL CONE PROTECTION ARCHITECTURE (CPA) SCHEME FOR WDM PASSIVE OPTICAL ACCESS NETWORKS --- p.35 / Chapter 4.1 --- Introduction --- p.35 / Chapter 4.2 --- Single-side Cone Protection Architecture (SS-CPA) --- p.36 / Chapter 4.2.1 --- Network topology of SS-CPA --- p.36 / Chapter 4.2.2 --- Wavelength assignment of SS-CPA --- p.36 / Chapter 4.2.3 --- Realization of remote node --- p.37 / Chapter 4.2.4 --- Realization of optical network unit --- p.39 / Chapter 4.2.5 --- Two types of failures --- p.40 / Chapter 4.2.6 --- Protection mechanism against failure --- p.40 / Chapter 4.2.6.1 --- Multi-failures of type I failure --- p.40 / Chapter 4.2.6.2 --- Type II failure --- p.40 / Chapter 4.2.7 --- Experimental demonstration --- p.41 / Chapter 4.2.8 --- Power budget --- p.42 / Chapter 4.2.9 --- Protection capability analysis --- p.42 / Chapter 4.2.10 --- Non-fully-connected case and its extensibility for addition --- p.42 / Chapter 4.2.11 --- Scalability --- p.43 / Chapter 4.2.12 --- Summary --- p.43 / Chapter 4.3 --- Comparison between GPA and SS-CPA scheme --- p.43 / Chapter 4.1 --- Resources comparison --- p.43 / Chapter 4.2 --- Protection capability comparison --- p.44 / Chapter 4.4 --- Concluding remarks --- p.45 / Chapter CHAPTER 5 --- MUL 77- WA VELENGTH MUL TICAST NETWORK IN PASSIVE OPTICAL NETWORK --- p.46 / Chapter 5.1 --- Introduction --- p.46 / Chapter 5.2 --- Organization of this chapter --- p.47 / Chapter 5.3 --- Simple Group Multicast Network (SGMN) scheme --- p.47 / Chapter 5.3.1 --- Network design principle --- p.47 / Chapter 5.3.2 --- Wavelength assignment of SGMN --- p.48 / Chapter 5.3.3 --- Realization of remote node --- p.49 / Chapter 5.3.3 --- Realization of optical network unit --- p.50 / Chapter 5.3.4 --- Power budget --- p.51 / Chapter 5.4 --- A mulTI- wa velength a ccess network with reconfigurable multicast …… --- p.51 / Chapter 5.4.1 --- Motivation --- p.51 / Chapter 5.4.2 --- Background --- p.51 / Chapter 5.4.3 --- Network design principle --- p.52 / Chapter 5.4.4 --- Wavelength assignment --- p.52 / Chapter 5.4.5 --- Remote Node design --- p.53 / Chapter 5.4.6 --- Optical network unit design --- p.54 / Chapter 5.4.7 --- Multicast connection pattern --- p.55 / Chapter 5.4.8 --- Multicast group selection in OLT --- p.57 / Chapter 5.4.9 --- Scalability --- p.57 / Chapter 5.4.10 --- Experimental configuration --- p.58 / Chapter 5.4.11 --- Concluding remarks --- p.59 / Chapter CHAPTER 6 --- CONCLUSIONS --- p.60 / LIST OF PUBLICATIONS: --- p.62 / REFERENCES: --- p.63

by Arion Ko Kin Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 101-[106]). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview --- p.1 / Chapter 1.2 --- Service Survivability Planning --- p.2 / Chapter 1.3 --- Categories of Outages --- p.3 / Chapter 1.4 --- Goals of Restoration --- p.4 / Chapter 1.5 --- Technology Impacts on Network Survivability --- p.5 / Chapter 1.6 --- Performance Models and Measures in Quantifying Network Sur- vivability --- p.6 / Chapter 1.7 --- Organization of Thesis --- p.6 / Chapter 2 --- Design and Implementation of A Survivable High-Speed Mul- timedia Network --- p.8 / Chapter 2.1 --- An Overview of CUM LAUDE NET --- p.8 / Chapter 2.2 --- The Network Architecture --- p.9 / Chapter 2.2.1 --- Architectural Overview --- p.9 / Chapter 2.2.2 --- Router-Node Design --- p.11 / Chapter 2.2.3 --- Buffer Allocation --- p.12 / Chapter 2.2.4 --- Buffer Transmission Priority --- p.14 / Chapter 2.2.5 --- Congestion Control --- p.15 / Chapter 2.3 --- Protocols --- p.16 / Chapter 2.3.1 --- Design Overview --- p.16 / Chapter 2.3.2 --- ACTA - The MAC Protocol --- p.17 / Chapter 2.3.3 --- Protocol Layering --- p.18 / Chapter 2.3.4 --- "Segment, Datagram and Packet Format" --- p.20 / Chapter 2.3.5 --- Fast Packet Routing --- p.22 / Chapter 2.3.6 --- Local Host NIU --- p.24 / Chapter 2.4 --- The Network Restoration Strategy --- p.25 / Chapter 2.4.1 --- The Dual-Ring Model and Assumptions --- p.26 / Chapter 2.4.2 --- Scenarios of Network Failure and Remedies --- p.26 / Chapter 2.4.3 --- Distributed Fault-Tolerant Algorithm --- p.26 / Chapter 2.4.4 --- Distributed Auto-Healing Algorithm --- p.28 / Chapter 2.4.5 --- The Network Management Signals --- p.31 / Chapter 2.5 --- Performance Evaluation --- p.32 / Chapter 2.5.1 --- Restoration Time --- p.32 / Chapter 2.5.2 --- Reliability Measures --- p.34 / Chapter 2.5.3 --- Network Availability During Restoration --- p.41 / Chapter 2.6 --- The Prototype --- p.42 / Chapter 2.7 --- Technical Problems Encountered --- p.45 / Chapter 2.8 --- Chapter Summary and Future Development --- p.46 / Chapter 3 --- A Simple Experimental Network Management Software - NET- MAN --- p.48 / Chapter 3.1 --- Introduction to NETMAN --- p.48 / Chapter 3.2 --- Network Management Basics --- p.49 / Chapter 3.2.1 --- The Level of Management Protocols --- p.49 / Chapter 3.2.2 --- Architecture Model --- p.51 / Chapter 3.2.3 --- TCP/IP Network Management Protocol Architecture --- p.53 / Chapter 3.2.4 --- A Standard Network Management Protocol On Internet - SNMP --- p.54 / Chapter 3.2.5 --- A Standard For Managed Information --- p.55 / Chapter 3.3 --- The CUM LAUDE Network Management Protocol Suite (CNMPS) --- p.56 / Chapter 3.3.1 --- The Architecture --- p.53 / Chapter 3.3.2 --- Goals of the CNMPS --- p.59 / Chapter 3.4 --- Highlights of NETMAN --- p.61 / Chapter 3.5 --- Functional Descriptions of NETMAN --- p.63 / Chapter 3.5.1 --- Topology Menu --- p.64 / Chapter 3.5.2 --- Fault Manager Menu --- p.65 / Chapter 3.5.3 --- Performance Meter Menu --- p.65 / Chapter 3.5.4 --- Gateway Utility Menu --- p.67 / Chapter 3.5.5 --- Tools Menu --- p.67 / Chapter 3.5.6 --- Help Menu --- p.68 / Chapter 3.6 --- Chapter Summary --- p.68 / Chapter 4 --- A Local Map Based (LMB) Self-Healing Scheme for Arbitrary Topology Networks --- p.70 / Chapter 4.1 --- Introduction --- p.79 / Chapter 4.2 --- An Overview of Existing DCS-Based Restoration Algorithms --- p.72 / Chapter 4.3 --- The Network Model and Assumptions --- p.74 / Chapter 4.4 --- Basics of the LMB Scheme --- p.75 / Chapter 4.4.1 --- Restoration Concepts --- p.75 / Chapter 4.4.2 --- Terminology --- p.76 / Chapter 4.4.3 --- Algorithm Parameters --- p.77 / Chapter 4.5 --- Performance Assessments --- p.78 / Chapter 4.6 --- The LMB Network Restoration Scheme --- p.80 / Chapter 4.6.1 --- Initialization - Local Map Building --- p.80 / Chapter 4.6.2 --- The LMB Restoration Messages Set --- p.81 / Chapter 4.6.3 --- Phase I - Local Map Update Phase --- p.81 / Chapter 4.6.4 --- Phase II - Update Acknowledgment Phase --- p.82 / Chapter 4.6.5 --- Phase III - Restoration and Confirmation Phase --- p.83 / Chapter 4.6.6 --- Phase IV - Cancellation Phase --- p.83 / Chapter 4.6.7 --- Re-Initialization --- p.84 / Chapter 4.6.8 --- Path Route Monitoring --- p.84 / Chapter 4.7 --- Performance Evaluation --- p.84 / Chapter 4.7.1 --- The Testbeds --- p.84 / Chapter 4.7.2 --- Simulation Results --- p.86 / Chapter 4.7.3 --- Storage Requirements --- p.89 / Chapter 4.8 --- The LMB Scheme on ATM and SONET environment --- p.92 / Chapter 4.9 --- Future Work --- p.94 / Chapter 4.10 --- Chapter Summary --- p.94 / Chapter 5 --- Conclusion and Future Work --- p.96 / Chapter 5.1 --- Conclusion --- p.95 / Chapter 5.2 --- Future Work --- p.99 / Bibliography --- p.101 / Chapter A --- Derivation of Communicative Probability --- p.107 / Chapter B --- List of Publications --- p.110

Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

No description available.

Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

Thesis (MSc (Mathematical Sciences. Computer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Since 2002 data tra c has overtaken voice tra c in volume [1]. Telecom / Network operators still generate most of their income carrying voice tra c. There is however a huge revenue potential in delivering reliable guaranteed data services. Network survivability and recovery from network failures are integral to network reliability. Due to the nature of the Internet, recovery from link failures needs to be distributed and dynamic in order to be scalable. Link failure recovery schemes are evaluated in terms of the survivability of the network, the optimal use of network resources, scalability, and the recovery time of such schemes. The need for recovery time to be improved is highlighted by real-time data tra c such as VoIP and video services carried over the Internet. The goal of this thesis is to examine existing link failure recovery schemes and evaluate the need for their extension, and to evaluate the performance of the proposed link failure recovery schemes. i / AFRIKAANSE OPSOMMING: Sedert 2002 het data verkeer die stem verkeer in volume verbygesteek [1]. Telekommunikasie / netwerk operateurs genereer egter steeds die meeste van hul inkomste met stem verkeer. Netwerk oorlewing en die herstel van netwerk mislukkings is integraal tot netwerk stabiliteit. Die samestelling van die Internet noodsaak dat die herstel van skakel mislukkings verspreid en dinamies van natuur moet wees. Die herstel-skema van skakel mislukkings word evalueer in terme van die oorleefbaarheid van die netwerk, die mees e ektiewe benutting van network bronne, aanpasbaarheid, en die herstel tydperk van die skema. Die vinnig moontlikste herstel tydperk word genoodsaak deur oombliklike data verkeer soos VoIP en beeld dienste wat oor die Internet gedra word. The doel van hierdie tesis is om bestaande skakel mislukking herstel skemas te evalueer, en dan verder ondersoek in te stel na hul uitbreiding. Daarna word die voorgestelde skakel mislukking skema se e ektiwiteit gemeet.

The convergence of recent technology advances opens the way to new ubiquitous environments, where network-enabled devices collectively form invisible pervasive computing and networking environments around the users. These users increasingly require extensive applications and capabilities from these devices. Recent approaches propose that cooperating service providers, at the edge of the network, offer these required capabilities (i.e services), instead of having them directly provided by the devices. Thus, the network evolves from a plain communication medium into an endless source of services. Such a service, namely an overlay application, is composed of multiple distributed application elements, which cooperate via a dynamic communication mesh, namely an overlay association. The Quality of Service (QoS) perceived by the users of an overlay application greatly depends on the QoS on the communication paths of the corresponding overlay association. This thesis asserts and shows that it is possible to provide QoS to an overlay application by using alternate Internet paths resulting from the compositions of independent consecutive paths. Moreover, this thesis also demonstrates that it is possible to discover, select and compose these independent paths in a distributed manner within an community comprising a limited large number of autonomous cooperating peers, such as the fore-mentioned service providers. Thus, the main contributions of this thesis are i) a comprehensive description and QoS characteristic analysis of these composite alternate paths, and ii) an original architecture, termed SPAD (Super-Peer based Alternate path Discovery), which allows the discovery and selection of these alternate paths in a distributed manner. SPAD is a fully distributed system with no single point of failure, which can be easily and incrementally deployed on the current Internet. It empowers the end-users at the edge of the network, allowing them to directly discover and utilize alternate paths.

O presente trabalho consiste na proposta de um novo protocolo de transporte para redes tolerantes a atrasos e desconexões (DTN - Delay Tolerant Network) chamado PTTA - Protocolo de Transporte Tolerante a Atrasos (em inglês - DTTP - Delay Tolerant Transport Protocol). Este protocolo tem o objetivo de oferecer uma confiabilidade estatística na entrega das informações em redes deste tipo. Para isso, serão utilizados Códigos Fontanais como técnica de correção de erros. Os resultados mostram as vantagens da utilização do PTTA. Este trabalho ainda propõe um mecanismo de controle da fonte adaptável para o PTTA a fim de limitar a quantidade de dados gerados pela origem (fonte). O esquema proposto almeja aumentar a diversidade das informações codificadas sem o aumento da carga na rede. Para atingir este objetivo o intervalo de geração e o TTL (Time To Live - Tempo de vida) das mensagens serão manipulados com base em algumas métricas da rede. A fim de validar a eficiência do mecanismo proposto, diferentes cenários foram testados utilizando os principais protocolos de roteamento para DTNs. Os resultados de desempenho foram obtidos levando em consideração o tamanho do buffer, o TTL das mensagens e a quantidade de informação redundante gerada na rede. Os resultados de simulações obtidos através do simulador ONE mostram que nos cenários avaliados, o PTTA alcança um aumento na taxa de entrega das informações em um menor tempo, quando comparado com outro protocolo de transporte sem confirmação, permitindo assim um ganho de desempenho na rede. / The present work consists in the proposal of a new transport protocol for delay tolerant networks and disconnections (DTN - Delay Tolerant Network) called DTTP - Delay Tolerant Transport Protocol (in portuguese – PTTA - Protocolo de Transporte Tolerante a Atrasos). This protocol aims to provide a statistical reliability in DTNs' information delivery. For this, we use fountain codes as error correction technique. The results show the advantages of using DTTP. This work also proposes an adaptive control mechanism for the DTTP source to limit the amount of generated data. The proposed scheme aims at increasing the diversity of encoded information without increasing the load on the network. To achieve this goal the messages generation interval and TTL (Time To Live) will be handled based on some network metrics. In order to validate the efficiency of the proposed mechanism, different scenarios will be tested using the main routing protocols for DTNs. The performance results were obtained taking into account the buffer size, messages TTL and the amount of redundant information generated on the network. The simulation results, obtained through The ONE simulator, show that in the evaluated scenarios PTTA achieves an increase in the information delivery rate in a shorter time compared to other transport protocol for confirmation, thus allowing a gain in the network performance.

O presente trabalho consiste na proposta de um novo protocolo de transporte para redes tolerantes a atrasos e desconexões (DTN - Delay Tolerant Network) chamado PTTA - Protocolo de Transporte Tolerante a Atrasos (em inglês - DTTP - Delay Tolerant Transport Protocol). Este protocolo tem o objetivo de oferecer uma confiabilidade estatística na entrega das informações em redes deste tipo. Para isso, serão utilizados Códigos Fontanais como técnica de correção de erros. Os resultados mostram as vantagens da utilização do PTTA. Este trabalho ainda propõe um mecanismo de controle da fonte adaptável para o PTTA a fim de limitar a quantidade de dados gerados pela origem (fonte). O esquema proposto almeja aumentar a diversidade das informações codificadas sem o aumento da carga na rede. Para atingir este objetivo o intervalo de geração e o TTL (Time To Live - Tempo de vida) das mensagens serão manipulados com base em algumas métricas da rede. A fim de validar a eficiência do mecanismo proposto, diferentes cenários foram testados utilizando os principais protocolos de roteamento para DTNs. Os resultados de desempenho foram obtidos levando em consideração o tamanho do buffer, o TTL das mensagens e a quantidade de informação redundante gerada na rede. Os resultados de simulações obtidos através do simulador ONE mostram que nos cenários avaliados, o PTTA alcança um aumento na taxa de entrega das informações em um menor tempo, quando comparado com outro protocolo de transporte sem confirmação, permitindo assim um ganho de desempenho na rede. / The present work consists in the proposal of a new transport protocol for delay tolerant networks and disconnections (DTN - Delay Tolerant Network) called DTTP - Delay Tolerant Transport Protocol (in portuguese – PTTA - Protocolo de Transporte Tolerante a Atrasos). This protocol aims to provide a statistical reliability in DTNs' information delivery. For this, we use fountain codes as error correction technique. The results show the advantages of using DTTP. This work also proposes an adaptive control mechanism for the DTTP source to limit the amount of generated data. The proposed scheme aims at increasing the diversity of encoded information without increasing the load on the network. To achieve this goal the messages generation interval and TTL (Time To Live) will be handled based on some network metrics. In order to validate the efficiency of the proposed mechanism, different scenarios will be tested using the main routing protocols for DTNs. The performance results were obtained taking into account the buffer size, messages TTL and the amount of redundant information generated on the network. The simulation results, obtained through The ONE simulator, show that in the evaluated scenarios PTTA achieves an increase in the information delivery rate in a shorter time compared to other transport protocol for confirmation, thus allowing a gain in the network performance.

In this thesis, we consider the k-edge connected L-hop-constrained network design problem. Given a weighted graph G=(N,E), a set D of pairs of terminal nodes, and two integers k,L > 1, it consists in finding in G the minimum cost subgraph containing at least k edge-disjoint paths of at most L edges between each pair in D. This problem is of great interest in today's telecommunication industry, where highly survivable networks need to be constructed.<p><p>We first study the particular case where the set of demands D is reduced to a single pair {s,t}. We propose an integer programming formulation for the problem, which consists in the st-cut and trivial inequalities, along with the so-called L-st-path-cut inequalities. We show that these three classes of inequalities completely describe the associated polytope when k=2 and L=2 or 3, and give necessary and sufficient conditions for them to be facet-defining. We also consider the dominant of the associated polytope, and discuss how the previous inequalities can be separated in polynomial time.<p><p>We then extend the complete and minimal description obtained above to any number k of required edge-disjoint L-st-paths, but when L=2 only. We devise a cutting plane algorithm to solve the problem, using the previous polynomial separations, and present some computational results.<p><p>After that, we consider the case where there is more than one demand in D. We first show that the problem is strongly NP-hard, for all L fixed, even when all the demands in D have one root node in common. For k=2 and L=2,3, we give an integer programming formulation, based on the previous constraints written for all pairs {s,t} in D. We then proceed by giving several new classes of facet-defining inequalities, valid for the problem in general, but more adapted to the rooted case. We propose separation procedures for these inequalities, which are embedded within a Branch-and-Cut algorithm to solve the problem when L=2,3. Extensive computational results from it are given and analyzed for both random and real instances.<p><p>Since those results appear less satisfactory in the case of arbitrary demands (non necessarily rooted), we present additional families of valid inequalites in that situation. Again, separation procedures are devised for them, and added to our previous Branch-and-Cut algorithm, in order to see the practical improvement granted by them.<p><p>Finally, we study the problem for greater values of L. In particular, when L=4, we propose new families of constraints for the problem of finding a subgraph that contains at least two L-st-paths either node-disjoint, or edge-disjoint. Using these, we obtain an integer programming formulation in the space of the design variables for each case.<p><p>------------------------------------------------<p><p>Dans cette thèse, nous considérons le problème de conception de réseau k-arete connexe à chemins L-bornés. Etant donné un graphe pondéré G=(N,E), un ensemble D de paires de noeuds terminaux, et deux entiers k,L > 1, ce problème consiste à trouver, dans G, un sous-graphe de cout minimum tel que, entre chaque paire dans D, il existe au moins k chemins arete-disjoints de longueur au plus L. Ce problème est d'un grand intéret dans l'industrie des télécommunications, où des réseaux hautement fiables doivent etre construits.<p><p>Nous étudions tout d'abord le cas particulier où l'ensemble des demandes D est réduit à une seule paire de noeuds. Nous proposons une formulation du problème sous forme de programme linéaire en nombres entiers, laquelle consiste en les inégalités triviales et de coupe, ainsi que les inégalités dites de L-chemin-coupe. Nous montrons que ces trois types d'inégalités décrivent complètement le polytope associé lorsque k=2 et L=2,3, et donnons des conditions nécessaires et suffisantes pour que celles-ci en définissent des facettes. Nous considérons également le dominant du polytope associé et discutons de la séparation polynomiale des trois classes précédentes.<p><p>Nous étendons alors cette description complète et minimale à tout nombre k de chemins arete-disjoints de longueur au plus 2. De plus, nous proposons un algorithme de plans coupants utilisant les précédentes séparations polynomiales, et en présentons quelques résultats calculatoires, pour tout k>1 et L=2,3.<p><p>Nous considérons ensuite le cas où plusieurs demandes se trouvent dans D. Nous montrons d'abord que le problème est fortement NP-dur, pour tout L fixé et ce, meme si les demandes sont toutes enracinées en un noeud. Pour k=2 et L=2,3, nous donnons une formulation du problème sous forme de programme linéaire en nombres entiers. Nous proposons également de nouvelles classes d'inégalités valides, pour lesquelles nous réalisons une étude faciale. Celles-ci sont alors séparées dans le cadre d'un algorithme de coupes et branchements pour résoudre des instances aléatoires et réelles du problème.<p><p>Enfin, nous étudions le problème pour de plus grandes valeurs de L. En particulier, lorsque L=4, nous donnons de nouvelles familles de contraintes pour le problème consistant à déterminer un sous-graphe contenant entre deux noeuds fixés au moins deux chemins de longueur au plus 4, que ceux-ci doivent etre arete-disjoints ou noeud-disjoints. Grace à ces dernières, nous parvenons à donner une formulation naturelle du problème dans chacun de ces deux cas. <p> / Doctorat en sciences, Spécialisation Informatique / info:eu-repo/semantics/nonPublished