Medium access control mechanisms for high speed metropolitan area networks

In this dissertation novel Medium Access Control mechanisms for High Speed Metropolitan Area networks are proposed and their performance is investigated under the presence of single and multiple priority classes of traffic. The proposed mechanisms are based on the Distributed Queue Dual Bus network, which has been adopted by the IEEE standardization committee as the 802.6 standard for Metropolitan Area Networks, and address most of its performance limitations. First, the Rotating Slot Generator scheme is introduced which uses the looped bus architecture that has been proposed for the 802.6 network. According to this scheme the responsibility for generating slots moves periodically from station to station around the loop. In this way, the positions of the stations relative to the slot generator change continuously, and therefore, there are no favorable locations on the busses. Then, two variations of a new bandwidth balancing mechanism, the NSW_BWB and ITU_NSW are introduced. Their main advantage is that their operation does not require the wastage of channel slots and for this reason they can converge very fast to the steady state, where the fair bandwidth allocation is achieved. Their performance and their ability to support multiple priority classes of traffic are thoroughly investigated. Analytic estimates for the stations\u27 throughputs and average segment delays are provided. Moreover, a novel, very effective priority mechanism is introduced which can guarantee almost immediate access for high priority traffic, regardless of the presence of lower priority traffic. Its performance is thoroughly investigated and its ability to support real time traffic, such as voice and video, is demonstrated. Finally, the performance under the presence of erasure nodes of the various mechanisms that have been proposed in this dissertation is examined and compared to the corresponding performance of the most prominent existing mechanisms

High speed protocols for dual bus and dual ring network architectures

In this dissertation, two channel access mechanisms providing fair and bandwidth efficient transmission on dual bus and dual ring networks with high bandwidth-latency product are proposed. In addition, two effective priority mechanisms are introduced to meet the throughput and delay requirements of the diverse arrays of applications that future high speed networks must support. For dual bus architectures, the Buffer Insertion Bandwidth Balancing (BI_BWB) mechanism and the Preemptive priority Bandwidth Balancing (P_BI_BWB) mechanism are proposed. BI_BWB can significantly improve the delay performance of remote stations. It achieves that by providing each station with a shift register into which the station can temporarily store the upstream stations\u27 transmitted packets and replace these packets with its own transmissions. P_BI_BWB, an enhancement of BI_BWB, is designed to introduce effective preemptive priorities. This mechanism eliminates the effect of low priority on high priority by buffering the low priority traffic into a shift register until the transmission of the high priority traffic is complete. For dual ring architectures, the Fair Bandwidth Allocation Mechanism (FBAM) and the Effective Priority Bandwidth Balancing (EP_BWB) mechanism are introduced. FBAM allows stations to reserve channel bandwidth on a continuous basis rather than wait until bandwidth starvation is observed. Consequently, FBAM does not have to deal with the difficult issue of identifying starvation, a serious drawback of other access mechanisms such as the Local and Global Fairness Algorithms (LFA and GFA, respectively). In addition, its operation requires a significantly smaller number of control bits in the access control field of the slot and its performance is less sensitive to system parameters. Moreover, FBAM demonstrates Max-Min flow control properties with respect to the allocation of bandwidth among competing traffic streams, which is a significant advantage of FBAM over all the previously proposed channel access mechanisms. EP_BWB, an enhancement of FBAM to support preemptive priorities, minimizes the effect of low priority on high priority and supports delay-sensitive traffic by enabling higher priority classes to preempt the transmissions of lower priority classes. Finally, the great potential of EP_BWB to support the interconnection of base stations on a distributed control wireless PCN carrying voice and data traffic is demonstrated

Fiber optic networks: fairness, access controls and prototyping

Fiber optic technologies enabling high-speed, high-capacity digital information transport have only been around for about 3 decades but in their short life have completely revolutionized global communications. To keep pace with the growing demand for digital communications and entertainment, fiber optic networks and technologies continue to grow and mature. As new applications in telecommunications, computer networking and entertainment emerge, reliability, scalability, and high Quality of Service (QoS) requirements are increasing the complexity of optical transport networks.;This dissertation is devoted to providing a discussion of existing and emerging technologies in modern optical communications networks. To this end, we first outline traditional telecommunication and data networks that enable high speed, long distance information transport. We examine various network architectures including mesh, ring and bus topologies of modern Local, Metropolitan and Wide area networks. We present some of the most successful technologies used in todays communications networks, outline their shortcomings and introduce promising new technologies to meet the demands of future transport networks.;The capacity of a single wavelength optical signal is 10 Gbps today and is likely to increase to over 100 Gbps as demonstrated in laboratory settings. In addition, Wavelength Division Multiplexing (WDM) techniques, able to support over 160 wavelengths on a single optical fiber, have effectively increased the capacity of a single optical fiber to well over 1 Tbps. However, user requirements are often of a sub-wavelength order. This mis-match between individual user requirements and single wavelength offerings necessitates bandwidth sharing mechanisms to efficiently multiplex multiple low rate streams on to high rate wavelength channels, called traffic grooming.;This dissertation examines traffic grooming in the context of circuit, packet, burst and trail switching paradigms. Of primary interest are the Media Access Control (MAC) protocols used to provide QoS and fairness in optical networks. We present a comprehensive discussion of the most recognized fairness models and MACs for ring and bus networks which lay the groundwork for the development of the Robust, Dynamic and Fair Network (RDFN) protocol for ring networks. The RDFN protocol is a novel solution to fairly share ring bandwidth for bursty asynchronous data traffic while providing bandwidth and delay guarantees for synchronous voice traffic.;We explain the light-trail (LT) architecture and technology introduced in [37] as a solution to providing high network resource utilization, seamless scalability and network transparency for metropolitan area networks. The goal of light-trails is to eliminate Optical Electronic Optical (O-E-O) conversion, minimize active switching, maximize wavelength utilization, and offer protocol and bit-rate transparency to address the growing demands placed on WDM networks. Light-trail technology is a physical layer architecture that combines commercially available optical components to allow multiple nodes along a lightpath to participate in time multiplexed communication without the need for burst or packet level switch reconfiguration. We present three medium access control protocols for light-trails that provide collision protection but do not consider fair network access. As an improvement to these light-trail MAC protocols we introduce the Token LT and light-trail Fair Access (LT-FA) MAC protocols and evaluate their performance. We illustrate how fairness is achieved and access delay guarantees are made to satisfy the bandwidth budget fairness model. The goal of light-trails and our access control solution is to combine commercially available components with emerging network technologies to provide a transparent, reliable and highly scalable communication network.;The second area of discussion in this dissertation deals with the rapid prototyping platform. We discuss how the reconfigurable rapid prototyping platform (RRPP) is being utilized to bridge the gap between academic research, education and industry. We provide details of the Real-time Radon transform and the Griffin parallel computing platform implemented using the RRPP. We discuss how the RRPP provides additional visibility to academic research initiatives and facilitates understanding of system level designs. As a proof of concept, we introduce the light-trail testbed developed at the High Speed Systems Engineering lab. We discuss how a light-trail test bed has been developed using the RRPP to provide additional insight on the real-world limitations of light-trail technology. We provide details on its operation and discuss the steps required to and decisions made to realize test-bed operation. Two applications are presented to illustrate the use of the LT-FA MAC in the test-bed and demonstrate streaming media over light-trails.;As a whole, this dissertation aims to provide a comprehensive discussion of current and future technologies and trends for optical communication networks. In addition, we provide media access control solutions for ring and bus networks to address fair resource sharing and access delay guarantees. The light-trail testbed demonstrates proof of concept and outlines system level design challenges for future optical networks

Extremely high data-rate, reliable network systems research

Significant progress was made over the year in the four focus areas of this research group: gigabit protocols, extensions of metropolitan protocols, parallel protocols, and distributed simulations. Two activities, a network management tool and the Carrier Sensed Multiple Access Collision Detection (CSMA/CD) protocol, have developed to the point that a patent is being applied for in the next year; a tool set for distributed simulation using the language SIMSCRIPT also has commercial potential and is to be further refined. The year's results for each of these areas are summarized and next year's activities are described

Multilevel Parallel Communications

The research reported in this thesis investigates the use of parallelism at multiple levels to realize high-speed networks that offer advantages in throughput, cost, reliability, and flexibility over alternative approaches. This research specifically considers use of parallelism at two levels: the upper level and the lower level. At the upper level, N protocol processors perform functions included in the transport and network layers. At the lower level, M channels provide data and physical layer functions. The resulting system provides very high bandwidth to an application. A key concept of this research is the use of replicated channels to provide a single, high bandwidth channel to a single application. The parallelism provided by the network is transparent to communicating applications, thus differentiating this strategy from schemes that provide a collection of disjoint channels between applications on different nodes. Another innovative aspect of this research is that parallelism is exploited at multiple layers of the network to provide high throughput not only at the physical layer, but also at upper protocol layers. Schedulers are used to distribute data from a single stream to multiple channels and to merge data from multiple channels to reconstruct a single coherent stream. High throughput is possible by providing the combined bandwidth of multiple channels to a single source and destination through use of parallelism at multiple protocol layers. This strategy is cost effective since systems can be built using standard technologies that benefit from the economies of a broad applications base. The exotic and revolutionary components needed in non-parallel approaches to build high speed networks are not required. The replicated channels can be used to achieve high reliability as well. Multilevel parallelism is flexible since the degree of parallelism provided at any level can be matched to protocol processing demands and application requirements

Performance Improvements for FDDI and CSMA/CD Protocols

The High-Performance Computing Initiative from the White House Office of Science and Technology Policy has defined 20 major challenges in science and engineering which are dependent on the solutions to a number of high-performance computing problems. One of the major areas of focus of this initiative is the development of gigabit rate networks to be used in environments such as the space station or a National Research and Educational Network (NREN). The strategy here is to use existing network designs as building blocks for achieving higher rates, with the ultimate goal being a gigabit rate network. Two strategies which contribute to achieving this goal are examined in detail.1 FDDI2 is a token ring network based on fiber optics capable of a 100 Mbps rate. Both media access (MAC) and physical layer modifications are considered. A method is presented which allows one to determine maximum utilization based on the token-holding timer settings. Simulation results show that employing the second counter-rotating ring in combination with destination removal has a multiplicative effect greater than the effect which either of the factors have individually on performance. Two 100 Mbps rings can handle loads in the range of 400 to 500 Mbps for traffic with a uniform distribution and fixed packet size. Performance is dependent on the number of nodes, improving as the number increases. A wide range of environments are examined to illustrate robustness, and a method of implementation is discussed

Delay analysis for wireless applications using a multiservice multiqueue processor sharing model

The ongoing development of wireless networks supporting multimedia applications requires service providers to efficiently deliver complex Quality of Service (QoS) requirements. The wide range of new applications in these networks significantly increases the difficulty of network design and dimensioning to meet QoS requirements. Medium Access Control (MAC) protocols affect QoS achieved by wireless networks. Research on analysis and performance evaluation is important for the efficient protocol design. As wireless networks feature scarce resources that are simultaneously shared by all users, processor sharing (PS) models were proposed for modelling resource sharing mechanisms in such systems. In this thesis, multi-priority MAC protocols are proposed for handling the various service traffic types. Then, an investigation of multiservice multiqueue PS models is undertaken to analyse the delay for some recently proposed wireless applications. We start with an introduction to MAC protocols for wireless networks which are specified in IEEE standards and then review scheduling algorithms which were proposed to work with the underlying MAC protocols to cooperatively achieve QoS goals. An overview of the relevant literature is given on PS models for performance analysis and evaluation of scheduling algorithms. We propose a multiservice multiqueue PS model using a scheduling scheme in multimedia wireless networks with a comprehensive description of the analytical solution. Firstly, we describe the existing multiqueue processor sharing (MPS) model, which uses a fixed service quantum at each queue, and correct a subtle incongruity in previous solutions presented in the literature. Secondly, a new scheduling framework is proposed to extend the previous MPS model to a general case. This newly proposed analytical approach is based on the idea that the service quantum arranged by a MAC scheduling controller to service data units can be priority-based. We obtain a closed-form expression for the mean delay of each service class in this model. In summary, our new approach simplifies MAC protocols for multimedia applications into an analytical model that includes more complex and realistic traffic models without compromising details of the protocol and significantly reduces the number of MAC headers, thus the overall average delay will be decreased. In response to using the studied multiservice multiqueue PS models, we apply the MPS model to two wireless applications: Push to Talk (PTT) service over GPRS/GSM networks and the Worldwide Interoperability for Microwave Access (WiMAX) networks. We investigate the uplink delay of PTT over traditional GPRS/GSM networks and the uplink delay for WiMAX Subscriber Station scheduler under a priority-based fair scheduling. MAC structures capable of supporting dynamically varying traffic are studied for the networks, especially, with the consideration of implementation issues. The model provides useful insights into the dynamic performance behaviours of GPRS/GSM and WiMAX networks with respect to various system parameters and comprehensive traffic conditions. We then evaluate the model under some different practical traffic scenarios. Through modelling of the operation of wireless access systems, under a variety of multimedia traffic, our analytical approaches provide practical analysis guidelines for wireless network dimensioning

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