9 research outputs found
Bandwidth management and quality of service
With the advent of bandwidth-hungry video and audio applications, demand for bandwidth is expected to exceed supply. Users will require more bandwidth and, as always, there are likely to be more users. As the Internet user base becomes more diverse, there is an increasing perception that Internet Service Providers (ISPs) should be able to differentiate between users, so that the specific needs of different types of users can be met. Differentiated services is seen as a possible solution to the bandwidth problem. Currently, however, the technology used on the Internet differentiates neither between users, nor between applications. The thesis focuses on current and anticipated bandwidth shortages on the Internet, and on the lack of a differentiated service. The aim is to identify methods of managing bandwidth and to investigate how these bandwidth management methods can be used to provide a differentiated service. The scope of the study is limited to networks using both Ethernet technology and the Internet Protocol (IP). Tile study is significant because it addresses current problems confronted by network managers. The key terms, Quality of Service (QoS) and bandwidth management, are defined. âQoSâ is equated to a differentiating system. Bandwidth management is defined as any method of controlling and allocating bandwidth. Installing more capacity is taken to be a method of bandwidth management. The review of literature concentrates on Ethernet/IP networks. It begins with a detailed examination of definitions and interpretations of the term Quality of Service and shows how the meaning changed over the last decade. The review then examines congestion control, including a survey of queuing methods. Priority queuing implemented in hardware is examined in detail, followed by a review of the ReSource reserVation Protocol (RSVP) and a new version of IP (lPv6). Finally, the new standards IEEE 802.1p and IEEE 802.1Q are outlined, and parts of ISO/IEC 15802-3 are analysed. The Integrated Services Architecture (ISA), Differentiated Services (DiffServ) and MultiProtocol Label Switching (MPLS) are seen as providing a theoretical framework for QoS development. The Open Systems Interconnection Reference Model (OSI model) is chosen as the preferred framework for investigating bandwidth management because it is more comprehensive than the alternative US Department of Defence Model (DoD model). A case study of the Edith Cowan University (ECU) data network illustrates current practice in network management. It provides concrete examples of some of the problems, methods and solutions identified in the literary review. Bandwidth management methods are identified and categorised based on the OSI layers in which they operate. Suggestions are given as to how some of these bandwidth management methods are, or can be used within current QoS architectures. The experimental work consists of two series of tests on small, experimental LANs. The tests are aimed at evaluating the effectiveness of IEEE 802.1 p prioritisation. The results suggest that in small Local Area Networks (LANs) prioritisation provides no benefit when Ethernet switches are lightly loaded
A NETWORK PATH ADVISING SERVICE
A common feature of emerging future Internet architectures is the ability for applications to select the path, or paths, their packets take between a source and destination. Unlike the current Internet architecture where routing protocols find a single (best) path between a source and destination, future Internet routing protocols will present applications with a set of paths and allow them to select the most appropriate path. Although this enables applications to be actively involved in the selection of the paths their packets travel, the huge number of potential paths and the need to know the current network conditions of each of the proposed paths will make it virtually impossible for applications to select the best set of paths, or just the best path.
To tackle this problem, we introduce a new Network Path Advising Service (NPAS) that helps future applications choose network paths. Given a set of possible paths, the NPAS service helps applications select appropriate paths based on both recent path measurements and end-to-end feedback collected from other applications. We describe the NPAS service abstraction, API calls, and a distributed architecture that achieves scalability by determining the most important things to monitor based on actual usage. By analyzing existing traffic patterns, we will demonstrate it is feasible for NPAS to monitor only a few nodes and links and yet be able to offer advice about the most important paths used by a high percentage of traffic. Finally, we describe a prototype implementation of the NPAS components as well as a simulation model used to evaluate the NPAS architecture
Klausurtagung des Instituts fĂŒr Telematik. Mainz 29.-31. MĂ€rz 1998
Der Bericht gibt einen Ăberblick ĂŒber aktuelle
Forschungsarbeiten des Instituts fĂŒr Telematik der UniversitĂ€t
Karlsruhe in den Bereichen Hochleistungskommunikation, verteilte
Systeme, Cooperation&Management und Telekooperation. Er ist in
zwei Teile gegliedert. Der erste beschreibt die persönlichen
Interessensgebiete der wissenschaftlichen Mitarbeiter. Danach folgt
eine Darstellung der Kooperationsprojekte des Instituts. Im Anhang
finden sich aktuelle Eigenveröffentlichungen der Mitarbeiter des
Instituts.
Der Tagungsband entstand im Rahmen der siebten Klausurtagung des
Instituts fĂŒr Telematik, die vom 29. bis zum 31. MĂ€rz 1998 in
Mainz abgehalten wurde
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Scalable and network aware video coding for advanced communications over heterogeneous networks
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityThis work addresses the issues concerned with the provision of scalable video services over heterogeneous networks particularly with regards to dynamic adaptation and userâs acceptable quality of service.
In order to provide and sustain an adaptive and network friendly multimedia communication service, a suite of techniques that achieved automatic scalability and adaptation are developed. These techniques are evaluated objectively and subjectively to assess the Quality of Service (QoS) provided to diverse users with variable constraints and dynamic resources. The research ensured the consideration of various levels of user acceptable QoS The techniques are further evaluated with view to establish their performance against state of the art scalable and non-scalable techniques.
To further improve the adaptability of the designed techniques, several experiments and real time simulations are conducted with the aim of determining the optimum performance with various coding parameters and scenarios. The coding parameters and scenarios are evaluated and analyzed to determine their performance using various types of video content and formats. Several algorithms are developed to provide a dynamic adaptation of coding tools and parameters to specific video content type, format and bandwidth of transmission.
Due to the nature of heterogeneous networks where channel conditions, terminals, users capabilities and preferences etc are unpredictably changing, hence limiting the adaptability of a specific technique adopted, a Dynamic Scalability Decision Making Algorithm (SADMA) is developed. The algorithm autonomously selects one of the designed scalability techniques basing its decision on the monitored and reported channel conditions. Experiments were conducted using a purpose-built heterogeneous network simulator and the network-aware selection of the scalability techniques is based on real time simulation results. A technique with a minimum delay, low bit-rate, low frame rate and low quality is adopted as a reactive measure to a predicted bad channel condition. If the use of the techniques is not favoured due to deteriorating channel conditions reported, a reduced layered stream or base layer is used. If the network status does not allow the use of the base layer, then the stream uses parameter identifiers with high efficiency to improve the scalability and adaptation of the video service.
To further improve the flexibility and efficiency of the algorithm, a dynamic de-blocking filter and lambda value selection are analyzed and introduced in the algorithm. Various methods, interfaces and algorithms are defined for transcoding from one technique to another and extracting sub-streams when the network conditions do not allow for the transmission of the entire bit-stream
Scalable Network Design and Management with Decentralized Software-defined Networking
Network softwarization is among the most significant innovations of computer networks in the last few decades. The lack of uniform and programmable interfaces for network management led to the design of OpenFlow protocol for the university campuses and enterprise networks. This breakthrough coupled with other similar efforts led to an emergence of two complementary but independent paradigms called software-defined networking (SDN) and network function virtualization (NFV). As of this writing, these paradigms are becoming the de-facto norms of wired and wireless networks alike. This dissertation mainly addresses the scalability aspect of SDN for multiple network types. Although centralized control and separation of control and data planes play a pivotal role for ease of network management, these concepts bring in many challenges as well. Scalability is among the most crucial challenges due to the unprecedented growth of computer networks in the past few years. Therefore, we strive to grapple with this problem in diverse networking scenarios and propose novel solutions by harnessing capabilities provided by SDN and other related technologies. Specifically, we present the techniques to deploy SDN at the Internet scale and to extend the concepts of softwarization for mobile access networks and vehicular networks. Multiple optimizations are employed to mitigate latency and other overheads that contribute to achieve performance gains. Additionally, by taking care of sparse connectivity and high mobility, the intrinsic constraints of centralization for wireless ad-hoc networks are addressed in a systematic manner. The state-of-the-art virtualization techniques are coupled with cloud computing methods to exploit the potential of softwarization in general and SDN in particular. Finally, by tapping into the capabilities of machine learning techniques, an SDN-based solution is proposed that inches closer towards the longstanding goal of self-driving networks. Extensive experiments performed on a large-scale testbed corroborates effectiveness of our approaches
Roteamento multicast multisessĂŁo: modelos e algoritmos
Multicast Technology has been studied over the last two decades and It has shown to be a
good approach to save network resources. Many approaches have been considered to solve
the multicast routing problem considering only one session and one source to attending
sessionâs demand, as well, multiple sessions with more than one source per session. In
this thesis, the multicast routing problem is explored taking in consideration the models
and the algorithms designed to solve it when where multiple sessions and sources. Two
new models are proposed with different focuses. First, a mono-objective model optimizing
residual capacity, Z, of the network subject to a budget is designed and the objective is to
maximize Z. Second, a multi-objective model is designed with three objective functions:
cost, Z and hops counting. Both models consider multisession scenario with one source
per session. Besides, a third model is examined. This model was designed to optimize
Z in a scenario with multiple sessions with support to more than one source per session.
An experimental analysis was realized over the models considered. For each model, a set
of algorithms were designed. First, an ACO, a Genetic algorithm, a GRASP and an ILS
algorithm were designed to solve the mono-objective model â optimizing Z subject to a
budget. Second, a set of algorithm were designed to solve the multi-objective model. The
classical approaches were used: NSGA2, ssNSGA2, SMS-EMOA, GDE3 and MOEA/D.
In addition, a transgenetic algorithm was designed to solve the problem and it was compared
against the classical approaches. This algorithm considers the use of subpopulations
during the evolution. Each subpopulation is based on a solution construction operator
guided by one of the objective functions. Some solutions are considered as elite solutions
and they are considered to be improved by a transposon operator. Eight versions of the
transgenetic algorithm were evaluated. Third, an algorithm was designed to solve the
problem with multiple sessions and multiple sources per sessions. This algorithm is based
on Voronoi Diagrams and it is called MMVD. The algorithm designed were evaluated on
large experimental analysis. The sample generated by each algorithm on the instances
were evaluated based on non-parametric statistical tests. The analysis performed indicates
that ILS and Genetic algorithm have outperformed the ACO and GRASP. The comparison between ILS and Genetic has shown that ILS has better processing time performance.
In the multi-objective scenario, the version of Transgenetic called cross0 has
shown to be statistically better than the other algorithms in most of the instances based
on the hypervolume and addictive/multiplicative epsilon quality indicators. Finally, the
MMVD algorithm has shown to be better than the algorithm from literature based on the
experimental analysis performed for the model with multiple session and multiple sources
per session.A tecnologia multicast tem sido amplamente estudada ao longo dos anos e apresenta-se
como uma solução para melhor utilização dos recursos da rede. Vårias abordagens jå
foram avaliadas para o problema de roteamento desde o uso de uma sessĂŁo com apenas
uma fonte a um cenĂĄrio com mĂșltiplas sessĂ”es e mĂșltiplas fontes por sessĂŁo. Neste trabalho,
Ă© feito um estudo dos modelos matemĂĄticos para o problema com mĂșltiplas sessĂ”es
e mĂșltiplas fontes. Dois modelos matemĂĄticos foram propostos: uma versĂŁo multissessĂŁo
mono-objetivo que visa a otimização da capacidade residual sujeito a um limite de
custo e uma versĂŁo multiobjetivo com trĂȘs funçÔes-objetivo. Ambos os modelos levam em
conta o cenĂĄrio multissessĂŁo com uma fonte por sessĂŁo. AlĂ©m disso, um estudo algorĂtmico
foi realizado sobre um modelo da literatura que utiliza mĂșltiplas fontes por sessĂŁo.
TrĂȘs conjuntos de algoritmos foram propostos. O primeiro conjunto trata do problema
mono-objetivo proposto e considera as abordagens ACO, Genético, GRASP e ILS. O segundo
conjunto consiste dos algoritmos propostos para o modelo multiobjetivo. Foram
projetados os seguintes algoritmos: NSGA2, ssNSGA2, GDE3, MOEA/D e SMS-EMOA.
Além disso, foi projetado um algoritmo transgenético com subpopulaçÔes baseadas em
operadores de criação de solução direcionados por objetivos do problema. Também foi
utilizado o conceito de soluçÔes de elite. No total, 8 versÔes do algoritmo transgenético foram
avaliadas. O terceiro conjunto de algoritmos consiste da heurĂstica MMVD proposta
para o modelo da literatura com mĂșltiplas fontes por sessĂŁo. Esta heurĂstica Ă© baseada no
uso de diagramas de Voronoi. O processo experimental foi realizado com amplo nĂșmero
de instùncias configuradas de modo a avaliar diferentes situaçÔes. Os resultados foram
comparados utilizando mĂ©todos estatĂsticos nĂŁo-paramĂ©tricos. A anĂĄlise final indicou que
o ILS e o Genético obtiveram resultados muito similares, entretanto o ILS possui melhor
tempo de processamento. A versão cross0 do algoritmo transgenético obteve o melhor
resultado em praticamente todos os cenĂĄrios avaliados. A heurĂstica MMVD obteve excelentes
resultados sobre algoritmos da literatura