[pt] Este trabalho aborda um estudo sobre o desempenho de uma rede de dados IP/MPLS, com a implementação dos protocolos de NGN e (Sinalização sobre IP), utilizando a arquitetura Diffserv para oferecimento de QoS. O objeto do estudo está adequado aos padrões do IETF, definidos para arquitetura de core de rede UMTS all-IP. São detalhados o conceito, a arquitetura e os fluxos de chamadas do padrão UMTS e revistos conceitos básicos dos protocolos envolvidos na solução. Para a implementação de QoS no laboratório proposto, são revistos também os principais mecanismos de controle de tráfego Diffserv. Utilizando roteadores, switch´s, emuladores de protocolos e ferramentas de gerência por classes, avalia-se o desempenho do tráfego de uma rede com a implementação de VoIP e SS7oIP. Para o cenário especificado, são estudados: classificação dos protocolos para diferentes fontes de tráfego, disciplinas de serviço, procurando-se obter medidas de desempenho que possam ser úteis em projetos de core de rede, com qualidade de serviço, que possuam as características propostas pelo IETF para o padrão UMTS. / [en] This work approaches a study about the performance of a data network IP/MPLS, with an implementation of NGN protocols (Signaling over IP), using the DiffServ architecture to offer the QoS. The purpose of the study is suitable to the IETF standards, determined by architecture of core network UMTS all-IP. The concept, the architecture and the flux of standards call UMTS are detailed. In order to implement the QoS in the proposed laboratory, the main mechanism of traffic DiffServ control are revised too. Using routers, switch´s, network emulators and classes´ management tools, the performance of a network traffic with the implementation of VoIP and SS7oIP is evaluated. To the specific cenary, are studied the classification protocols for different traffic sources and disciplines of service, searching to get the measures of perform that can be useful in core network projects, with quality of service, that own the proposal characteristics by IETF to UMTS standard.

A Mobile Ad Hoc Network (MANET) is a shared wireless network without any infrastructure, consisting of mobile nodes connected by wireless links. The nodes are free to move and organize themselves arbitrarily. The nodes in the network are therefore depending on each other in order to communicate over multiple hops. Due to the physical characteristics of wireless networks, the channel is time-varying, which makes it hard to both predict and sustain a bit rate level. The nodes’ mobility causes topology changes, and further load and capacity variations. Traditional usage areas are battlefield and disaster areas, while new areas like extended network coverage and gaming are emerging. Quality of Service (QoS) is needed in every network in order to differentiate traffic with different performance requirements, e.g. voice and e-mail applications. Providing QoS in wireless environments with varying conditions is complex, and hard guarantees can not be given. Consequently, the aim is to give differentiated treatment to traffic with different performance requirements. In addition, we can not study the MANET without considering fixed networks. Communication with fixed networks is important, for example by accessing the Internet. In this thesis the Differentiated Services (DiffServ) architecture is applied and adapted to MANETs. Using the same QoS architecture will ease the transition between the wireless and wired domain. But the special characteristics of wireless networks require modifications to the original DiffServ architecture. In investigations there was found restrictions on the number of classes to use, and this number was dependent on the type of traffic in the network. A QoS architecture based on the DiffServ framework is proposed, with an admission control based on the concept of shadow classes, and Explicit Congestion Notification (ECN) to avoid congestion. New flows are tested in a shadow class before getting admission to the network and its designated class. The shadow class has the same scheduling properties as the designated class, but is differentiated by a higher drop probability in the buffers. Both the admission control and ECN are thus build on the same principle by controlling the load from probabilistic functions in the buffers, and are studied to find their individual and combined effects. In wireless environments the probability of a packet loss increases with the number of hops, which gives services an unpredictable performance for users. A predictable service, independent of number of hops, is provided by scheduling based on the path information; the packets are differentiated based on the number of hops made or left to make, increasing the predictability at the cost of performance.

In this research, we propose a framework for measurement-based traffic engineering and connection admission control in radio access networks based on the Internet Protocol (IP). This framework is evaluated by simulation using the popular network simulator ns-2. The framework is adaptive to changes in the network load and can distinguish between different types of service. All traffic engineering decisions are made by edge routers (ERs) at the rim of the network domain. Multiple disjoint paths are configured between those ERs. Network state information is gathered in two different fashions. We evaluate a scheme based on the states of the queues on each alternative path and a scheme based on end-to-end probe packet transmission characteristics on each alternative path. Both schemes are compared to a shortest path first (SPF) routing approach.

Packet reordering is generally considered to have negative impact on network performance. In this thesis, the packet reordering is used to assist TCP to recover faster in RED-enabled packet switched networks. The RED queue management prevents networks from congestion by dropping packets with a probability earlier than the time when congestion would actually occur. After a RED router drops a packet, packer reordering is introduced during TCP¡¦s recovery process. A new, simple buffer mechanism, called RED with Recovery Queue or R2Q, is proposed to create this type of packet reordering on behalf of TCP with the objective of accelerating TCP¡¦s recovery and thus improving the overall network performance. In R2Q, the original RED queue is segmented into two sub-queues. The first sub-queue remains the function of the original RED while the second picks up the packets discarded by the first. Then, scheduling of the second-chance transmission of the packets in the secondary sub-queue is the key in achieving our objective. In this thesis, we considered two scheduling schemes: priority and weighted round robin. To evaluate the performance of R2Q with these two scheduling schemes, we implemented and evaluated them in the J-Sim network simulation environment. The well-known dumbbell network topology was adopted and we varied different parameters, such as round-trip time, bottleneck bandwidth, buffer size, WRR weight and so on, in order to understand how R2Q performs under different network configurations. We found that R2Q is more effective in the networks of sufficient buffer and larger product of RTT and bandwidth. With WRR, we may achieve as much as 2% improvement over the original RED. The improvement may be more in networks of even higher speed.

Existing edge and core routers in DiffServ networks require an effective scheduling mechanism. In this thesis, we design and implement a DiffServ scheduler on Linux platform to provide QoS for different PHB requirements. We first modify the PDD model proposed by Dovrolis, and then develop two new scheduling algorithms. The first algorithm is referred to as Priority Queue with Quantum (PQWQ) and the second one is referred to as Average Delay Queue (ADQ). PQWQ can provide lower delay for EF traffic than Deficit Round Robin (DRR), and higher network utilization than Priority Queue (PQ) with EF Token Bucket. In addition, PQWQ can guarantee a minimum bandwidth for AF and Default PHBs and avoid starvation in case of low priority PHBs. The second scheduler, ADQ, is designed to provide different levels of delay for AF classes. The average delays of the four AF classes can be proportional by adjusting the Delay Differentiation Parameter (DDP). This proportional scheme may allow the higher priority class to send packets more quickly, and therefore achieve higher QoS. Finally, we implement the two schedulers, PQWQ and ADQ, on Linux platform. We adopt share buffer scheme for AF PHB. Share buffer management can effectively improve the buffer utilization and avoid the unnecessary packet dropping due to the unfair buffer allocation. From the experimental results, we can observe that the new DiffServ schedulers not only provide lower delay and higher bandwidth utilization for EF PHB, but also achieve proportional delay among different AF classes.

In a DiffServ networks, edge and core router classify traffic flows into different PHBs and provide different QoS for the classified flows. In order to achieve satisfactory QoS guarantee, many packet schedulers were proposed. However IETF have not formally standardized an appropriate and effective packet scheduler to minimize the jitter for real-time traffic. In RFC, EF flows are characterized with low-latency, low packet loss rate, and low jitter. Therefore, real-time traffic is often classified into EF flow. By considering the characteristics of real-time traffic, it is not appropriate to forward packets either too fast or too slow. Hence, in this Thesis, we propose a mechanism in which each packet is attached with its own per-hop queuing delay. If a packet is forwarded within its own per-hop queuing delay, we say the packet may arrive too early (credit accumulation). If a packet is forwarded beyond its own per-hop queuing delay, we say the packet has late arrival (deficit accumulation). The Credit/Deficit information can be stored in the IPv6 optional header so that it can pass through the whole networks. If we can minimize the Credit/Deficit, the jitter can be minimized too. Our design is based on a modified WFQ by adding functions such as estimated queuing delay and dynamic class changes. The dynamic class changes allow EF packets to switch among queues to achieve lower jitter and constant delay. We first implement the traditional WFQ scheduler on Linux platform and then followed by the implementation of the Credit/Deficit WFQ (CDWFQ). The experimental results have shown that CDWFQ can provide nearly constant queuing delay, lower packet loss rate, and lower jitter for EF traffic flows.

Zugl.: Karlsruhe, Univ., Diss., 2007

Made available in DSpace on 2014-06-12T15:59:17Z (GMT). No. of bitstreams: 2 arquivo4992_1.pdf: 465621 bytes, checksum: beb55c17d095bd73e42ae404d38057fa (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2002 / A crescente demanda e o explosivo crescimento da Internet está impondo novos desafios para a garantia de serviços em termos de performance, confiabilidade e Qualidade de Serviço (QoS). Muitas aplicações de missão crítica que dependem das tecnologias de rede não podem funcionar sem garantias expressas de entrega. Entretanto, as redes de dados atuais não oferecem nenhuma garantia de que as exigências feitas a nível de serviço possam ser garantidas sem algum tipo de degradação a qualquer hora, do dia ou da noite, a despeito de outros usuários da rede. Para atender essas exigências, a infra-estrutura da rede precisa ser melhorada com novas tecnologias que ofereçam aos operadores de rede ferramentas para controlar o comportamento da mesma. Juntas, as capacidades oferecidas pela Engenharia de Tráfego, pelo MPLS (Multiprotocol Label Switching) e pelo DiffServ possibilitam o controle e o balanceamento de carga na rede necessários à entrega de serviço de acordo com contratos personalizados. Este trabalho apresenta o MPLS associado à Engenharia de Tráfego como solução para o problema de alocação ineficiente dos recursos em uma rede e o conseqüente congestionamento provocado por tal problema. O esquema de encaminhamento de pacotes do MPLS é empregado como estratégia para minimizar o congestionamento ou alternativamente maximizar a utilização dos recursos, através da alocação eficiente dos mesmos, garantindo, num ambiente com diferenciação de serviço, uma melhor Qualidade de Serviço em termos de redução na perda de pacotes, no atraso e na variação de atraso, e no aumento da vazão agregada

A traffic conditioner is an element of the Differentiated Services architecture. This architecture is used to regulate quality of service in computer networks. Five traffic conditioners were selected for the study. These include the token bucket marker and four conditioners described in RFCs. The contribution of this dissertation is two-fold. Firstly, it presents process algebra models of the five identified traffic conditioners. These models provide succinct descriptions of the conditioners thereby highlighting essential features. The models are, however, not intended for model checking purposes, but rather serve as a convenient pedagogical device. The second and main contribution of the dissertation is a simulation study to investigate the relative performance of the five traffic conditioners across a range of simulated scenarios in which traffic patterns and subscription levels are varied in a fixed network topology. Two performance measures—TargetRatio and GreenRatio—are defined, justified, and used to compare the traffic conditioners. The GreenRatio measure was found to be more discriminating than the TargetRatio measure. A variant of the GreenRatio measure was used to further illuminate the differences between conditioners. The simulation results suggest that the performance of the conditioners are sensitive to parameter values such as token bucket size and that bursty traffic patterns are particularly sensitive to these parameters. Under such bursty conditions, these parameters should be chosen with care. / Dissertation (MSc (Computer Science))--University of Pretoria, 2007. / Computer Science / unrestricted

The development of 3G (the 3rd generation telecommunication) value-added services brings higher requirements of Quality of Service (QoS). Wideband Code Division Multiple Access (WCDMA) is one of three 3G standards, and enhancement of QoS for WCDMA Core Network (CN) becomes more and more important for users and carriers. The dissertation focuses on enhancement of QoS for WCDMA CN. The purpose is to realize the DiffServ (Differentiated Services) model of QoS for WCDMA CN. Based on the parallelism characteristic of Network Processors (NPs), the NP programming model is classified as Pool of Threads (POTs) and Hyper Task Chaining (HTC). In this study, an integrated programming model that combines both of the two models was designed. This model has highly efficient and flexible features, and also solves the problems of sharing conflicts and packet ordering. We used this model as the programming model to realize DiffServ QoS for WCDMA CN. The realization mechanism of the DiffServ model mainly consists of buffer management, packet scheduling and packet classification algorithms based on NPs. First, we proposed an adaptive buffer management algorithm called Packet Adaptive Fair Dropping (PAFD), which takes into consideration of both fairness and throughput, and has smooth service curves. Then, an improved packet scheduling algorithm called Priority-based Weighted Fair Queuing (PWFQ) was introduced to ensure the fairness of packet scheduling and reduce queue time of data packets. At the same time, the delay and jitter are also maintained in a small range. Thirdly, a multi-dimensional packet classification algorithm called Classification Based on Network Processors (CBNPs) was designed. It effectively reduces the memory access and storage space, and provides less time and space complexity. Lastly, an integrated hardware and software system of the DiffServ model of QoS for WCDMA CN was proposed. It was implemented on the NP IXP2400. According to the corresponding experiment results, the proposed system significantly enhanced QoS for WCDMA CN. It extensively improves consistent response time, display distortion and sound image synchronization, and thus increases network efficiency and saves network resource.