23 research outputs found

    Fiber optic networks: fairness, access controls and prototyping

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    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

    Performance Improvements for FDDI and CSMA/CD Protocols

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    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

    Future benefits and applications of intelligent on-board processing to VSAT services

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    The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

    Multilevel Parallel Communications

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    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

    HIGHLY SYNCHRONOUS COMMUNICATION - CHARACTERIZATION, MODELING AND CONTROL

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    There exists a class of systems with requirements for real-time data delivery, limits on end-to-end delay, and limits on jitter. These systems can have components distributed across a wide area. In addition, the components distributed across a wide area require that the arrival and departure of data occur synchronously. To support these classes of systems, the communication systems must be able to transmit the required information within a pre-determined window of time. Due to the synchronous nature and requirements of these classes of systems, they are referred to as being Synchronous Dependent (SD). This research models and characterizes a serial communication link for application in a strict time constraint environment. These applications will also have limitations on jitter and delay, relative to the need to synchronize with other components of the system. Additionally, the research provides the modeling of users that utilize applications with relaxed constraints. The communication link will be able to support multiple users with varying requirements, from highly periodic control data to aperiodic general data. The network link is a modified T-channel, with resource reservation applying to both bandwidth and size allocation of a data frame. In contrast to a standard T-channel, the link has adjustable channel sizes, as well as the capability to shift a transmission out of the assigned channel into a channel either earlier or later than the previously assigned channel. In addition, a user may use more than one consecutive channel for the transmission of a single instance of information, i.e., multiple channels can be viewed as concatenated for use by a single user. The purpose of the channel is to provide a dedicated time slot available to the user that needs to transmit at a specific time that is also periodic. Through the modeling of the user's communications across the link, it is possible to examine the potential effects of the various characteristics of the individual user on the other users requesting access to the link. Assuming no adverse affects and to insure that time sensitive data are delivered on time, a method to determine the acceptability of the admission of the given user has been designed to determine which users will have access to the link and those that will not

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

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    La r脿pida evoluci贸 d鈥橧nternet i l鈥櫭爉plia gamma de noves aplicacions (per exemple, multim猫dia, videoconfer猫ncia, jocs en l铆nia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A m茅s, algunes d鈥檃questes aplicacions demanden grans quantitats de recursos d鈥檃mple de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexaci贸 per divisi贸 de longitud d鈥檕na (WDM) en els anys noranta va fer molt rendible la disponibilitat d鈥檃mple de banda. Avui dia, les tecnologies de commutaci贸 貌ptica de circuits s贸n predominants en el nucli de la xarxa, les quals permeten la configuraci贸 de canals (lightpaths) a trav茅s de la xarxa. No obstant aix貌, la granularitat d鈥檃quests canals ocupa tota la longitud d鈥檕na, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d鈥檕na). Segons la comunitat cient铆fica, 茅s necessari augmentar la transpar猫ncia dels protocols, aix铆 com millorar l鈥檃provisionament d鈥檃mple de banda de forma din脿mica. Per tal de fer aix貌 realitat, 茅s necessari desenvolupar noves arquitectures. La commutaci贸 貌ptica de r脿fegues i de paquets (OBS/OPS), s贸n dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d鈥檕na. En primer lloc, aprofundim en la naturalesa sense connexi贸 en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a r脿fega. A m茅s, les col路lisions entre r脿fegues degraden el rendiment de la xarxa fins i tot a c脿rregues molt baixes. Per fer front a aquestes col路lisions, es proposa un esquema de resoluci贸 de col路lisions pro actiu basat en un algorisme d鈥檈ncaminament i assignaci贸 de longitud d鈥檕na (RWA) que balanceja de forma autom脿tica i distribu茂da la c脿rrega en la xarxa. En aquest protocol, el RWA i la transmissi贸 de r脿fegues es basen en l鈥檈xplotaci贸 i exploraci贸 de regles de commutaci贸 que incorporen informaci贸 sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s鈥檜tilitzen dos tipus de paquets de control per a l鈥檈ncaminament de les r脿fegues i l鈥檃ctualitzaci贸 de les regles de commutaci贸, respectivament. Per analitzar els beneficis del nou algorisme, s鈥檜tilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el m猫tode proposat millora en diferents marges la resta d鈥檃lgorismes RWA en funci贸 de la topologia i sense penalitzar altres par脿metres com el retard extrem a extrem. La segona contribuci贸 proposa una arquitectura h铆brida sense i orientada a connexi贸 sobre la base d鈥檜n protocol de control d鈥檃cc茅s al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos m猫todes d鈥檃cc茅s: arbitratge de cua (QA) per a la transmissi贸 de r脿fegues sense connexi贸, i pre-arbitratge (PA) per serveis TDM orientats a connexi贸. Aquesta arquitectura permet una 脿mplia gamma d鈥檃plicacions sensibles al retard i al bloqueig. Els resultats avaluats a trav茅s de simulacions mostren que en l鈥檃cc茅s QA, les r脿fegues de m茅s alta prioritat tenen garantides zero p猫rdues i lat猫ncies d鈥檃cc茅s molt baixes. Pel que fa a l鈥檃cc茅s PA, es reporta que la duplicaci贸 de la c脿rrega TDM augmenta en m茅s d鈥檜n ordre la probabilitat de bloqueig, per貌 sense afectar en la mateixa mesura les r脿fegues sense connexi贸. En aquest cap铆tol tamb茅 es tracten dos dels problemes relacionats amb l鈥檃rquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matem脿tic per aproximar el retard d鈥檃cc茅s inferior i superior com a conseq眉猫ncia de l鈥檃cc茅s QA. En segon lloc, es formula matem脿ticament la generaci贸 i optimitzaci贸 de les topologies virtuals que suporten el protocol per a l鈥檈scenari amb tr脿fic est脿tic. Finalment, l鈥櫭簂tima contribuci贸 explora els beneficis d鈥檜na arquitectura de xarxa 貌ptica per temps compartit (TSON) basada en elements de c脿lcul de camins (PCE) centralitzats per tal d鈥檈vitar col路lisions en la xarxa. Aquesta arquitectura permet garantir l鈥檃provisionament orientat a connexi贸 de canals sub-longitud d鈥檕na. En aquest cap铆tol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa dep猫n en gran mesura de l鈥檃ssignaci贸 i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d鈥檃ssignaci贸 de ranures temporals i es comparen amb les corresponents formulacions de programaci贸 lineal (ILP) per al cas est脿tic. Per al cas de tr脿fic din脿mic, proposem i avaluem mitjan莽ant simulaci贸 diferents heur铆stiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freq眉encial a l鈥檋ora d鈥檃ssignar 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

    On-board B-ISDN fast packet switching architectures. Phase 1: Study

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    The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs

    Optical fibre distributed access transmission systems (OFDATS)

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    Application of Asynchronous Transfer Mode (Atm) technology to Picture Archiving and Communication Systems (Pacs): A survey

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    Broadband Integrated Services Digital Network (R-ISDN) provides a range of narrowband and broad-band services for voice, video, and multimedia. Asynchronous Transfer Mode (ATM) has been selected by the standards bodies as the transfer mode for implementing B-ISDN; The ability to digitize images has lead to the prospect of reducing the physical space requirements, material costs, and manual labor of traditional film handling tasks in hospitals. The system which handles the acquisition, storage, and transmission of medical images is called a Picture Archiving and Communication System (PACS). The transmission system will directly impact the speed of image transfer. Today the most common transmission means used by acquisition and display station products is Ethernet. However, when considering network media, it is important to consider what the long term needs will be. Although ATM is a new standard, it is showing signs of becoming the next logical step to meet the needs of high speed networks; This thesis is a survey on ATM, and PACS. All the concepts involved in developing a PACS are presented in an orderly manner. It presents the recent developments in ATM, its applicability to PACS and the issues to be resolved for realising an ATM-based complete PACS. This work will be useful in providing the latest information, for any future research on ATM-based networks, and PACS
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