Multi-Protocol Label Switching (MPLS), a label swapping and forwarding technology proposed by IETF, is very suitable for the backbone of the next-generation Internet. MPLS has the advantages in improving the performance of network-layer routing and increasing network scalability as well. To provide more reliable delivery in MPLS networks, it is necessary for every label switch router (LSR) to perform a fast recovery mechanism after link failures. It is also required for an LSR to support the functions of failure detection, failure notification, and protection mechanisms in each label switched path (LSP). Therefore, different kinds of recovery schemes in previous literatures have been proposed to enhance the reliability of MPLS networks when a link failure occurs in the primary LSP. In this thesis, we focus on the comparisons of three famous recovery mechanisms, Makam, Haskin, and Hundessa approach. By investigating different locations of link failure, the influences of the three approaches individually on the TCP performance are our major concerns, especially under different TCP versions. Finally, we use the MPLS Network Simulator (MNS) to verify our observations. Four different TCP versions, including TCP-Tahoe, TCP-Reno, TCP-NewReno, and TCP-SACK, are employed in our simulator. From the simulation results, the characteristics of congestion control when using different TCP versions are discussed. Without applying fast retransmission and fast recovery, the average throughput of TCP-Tahoe is the smallest, as compared to that of other TCP versions. In addition, multiple packet losses in the period of link failures would largely downgrade the performance of average throughput, no matter which TCP version (TCP-NewReno or TCP-Reno) is employed. Using Makam approach, we found out that the average throughput becomes better when the location of link failures is close to the ingress node.

MPLS, the next-generation backbone architecture, can speed up packet forwarding via label switching. However, if the traversed LSPs (Label Switching Paths) are in congestion, traffic may encounter serious throughput degradation due to packet loss. This performance degradation may become worse and worse unless another forwarding LSP for these traffic flows are allocated. Moreover, in this Thesis, we propose a preemption mechanism for higher-priority flows to obtain necessary resources (the bandwidth of a LSP) by preempting low-priority traffic flows. In the multiple-flow preemption mechanism, several LSPs between Ingress router and Egress router are established to forward traffic flows. Some of these traffic flows are higher priority with stringent QoS requirements. If no satisfactory throughput can be met, Egress router would have to feedback average throughput values to Ingress router, which in turn decides how many lower-priority traffic flows should be preempted and moved to another LSP. Consequently, Ingress router has to send bandwidth reservation messages to reserve bandwidth just released by those lower-priority flows. After that, every core router can process these MPLS packets with specified traffic class to meet their QoS requirements. Finally, for the purpose of demonstration, we embed multiple flow preemption modules into MNS simulator and use it to run some experiments. Since in our scheme, it is not necessary to reserve bandwidth for higher-priority traffic flows in advance, the overall bandwidth utilization can be increased. Furthermore, the higher-priority flows can meet their QoS requirements by preempting the lower-priority flows whenever it is needed.

In this thesis, we propose a dynamic traffic adjustment scheme for end-to-end proportional differentiated services (EEPDS) on MPLS networks. When the Egress LSR (Label Switch Router) first observes that the proportional ratio of multiple flows could not be maintained, it will locate the performance bottlenecks by sending control messages to all the traversed LSR. In the proposed scheme, the identified bottleneck routers may have to drop the packets of traffic flows that do not require any QoS assurance (for example, the best-effort flows). Moreover, if dropping packets of the best-effort flows could not meet the goals of maintaining proportional ratios, the Ingress LSR would have to shape the traffic rates of sending flows proportionally based on the throughput values observed by the Egress LSR. Once a bottleneck router regains its sufficient bandwidth released by other traffic flows, it will send out control packets to notify the Ingress LSR to recover the original sending rates. Eventually, the proposed EEPDS mechanism can meet the goals of maintaining the proportional ratios by dynamically tuning the traffic flows. For the purpose of demonstration, we implement the EEPDS scheme by using MNS simulator. According to the experimental results, the EEPDS scheme has shown that it can meet the proportional ratios of multiple traffic flows even under severe network congestions, where multiple performance bottlenecks may occur. Finally, we observe that the processing overhead of the proposed EEPDS scheme is very small, since it is triggered only when the Egress LSR detects the situation of unsatisfied proportional ratios.

The advent of Internet and the globalization have modified the forms of communication in the world and the enterprises. All this has brought the search of facilities of communications permanents and secures with quality of service to improve the Internet The studies of the news networks with MPLS are in a process that consists in finding news focus to improve the quality of service and rerouting. This thesis consists in analyzing and simulates MPLS with DiffServ to demonstrate that the use of the L-LSP is a good solution to improve the throughput in the network. The other side, it proposes a new method for updating time to rerouting in the network uses OSPF. Finally, it does an analysis and simulation of the network behavior, in case of the fail a link. It is to say the resilence of the network.

M. Tech. Electrical Engineering. / Discusses the study as limited to the formal specification/modelling and formal verification of protocols proposed and applicable to the initial network entry procedure in WiMAX networks. Secondly, formal specification of the existing protocols under consideration will be based on their informal specification available in the literature and not on proprietary protocols for which little or no information is available. Thirdly, this research work does not intend to wipe out the state space explosion problem but rather applies existing optimization techniques to supress it. Finally, the study does not assess the usability performance impact of the proposed security scheme and thus recommends that this analysis should be done as future work to evaluate the functionality and soundness of deploying the proposed security scheme.

There is currently much work focused on developing packet-switched optical networks to overcome the limitations of existing optical networks. Switch design for packet-switched optical networks is particularly challenging, in part due to the lack of a practical optical memory system. As a result, optical labels and all-optical label processing have attracted much attention. This thesis examines a crucial label processing component of an optical packet switch, namely the label swapper. / In this thesis, three different tabletop topologies for low-cost all-optical swapping of spectral amplitude code labels for packet-switched networks are examined in a proof-of-concept phase. The first uses cross-absorption modulation in an electro-absorption modulator within a semiconductor fiber ring laser (SFRL), the second uses cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) within an SFRL, and the third makes use of XGM in a SOA as well as injection locking in a Fabry-Perot laser diode for wavelength conversion. The benefits and limitations of each approach as well as future improvements are discussed. Building on these results, a high-performance integrated version of XGM swapper is designed, simulated, and masks are produced for fabrication using indium phosphide technology.

No description available.

Currently, a viable solution to provide multicast provision over a multiprotocol label switch with traffic engineering (MPLS-TE) domain is unavailable because of the missing link able to couple multicast traffic distribution with an MPLS-TE enabled network. This is due to the limited or less research investigation that was done in this area. Most of the investigation methods tackle the problem individually such as deploying internet protocol (IP) multicast in a plain network or MPLS domain but without considering a combination of both technologies that is aware of differentiated services requirements. This thesis presents an alternative solution for the multicast differentiated services provision problem over a MPLS-TE enabled network. The approach is exposed and analyzed through a practical solution that was developed within a network simulation environment. The research presented in this thesis orchestrates the already available technologies offered by the multicast protocols suite and differentiated services (DiffServ) aware MPLS-TE that allows applying separately the constraint-based routing and admission control to different classes of services. The novelty and solution of this thesis relies on using MPLS constraint-based routing concepts (e.g.traffic trunks) in order to solve TE issues revealed during multicast traffic distribution.

Στην εργασία παρουσιάζεται η μελέτη, η πιστοποίηση και η εφαρμογή των μηχανισμών εκείνων που οδηγούν στην παροχή end-to-end QoS σε ενοποιημένα L2 και MPLS δίκτυα. / In a real IP network such as the Internet, the basic type of service offered is the best effort one. In the best effort service all packets are treated equally and there are no guarantees, variations or attempt to enforce justice. However, the network seeks to promote as much traffic as possible with “reasonable” quality. Network congestion is a frequent phenomenon that is introduced when a network device stores packets at the output queue as it receives more packets from those that it can transmit. During congestion packets suffer from delay and once the output queue becomes full, these packets are dropped. However, there are applications that require certain guarantees (especially regarding delay and packet drops) such as real-time data transmission applications (e.g. IP telephony, voice over IP) and videoconference. Quality guarantees for these applications can be ensured if they can cross empty or nearempty network queues. This can only be achieved through mechanisms that can ensure the capacity and availability of the network queues. A means to provide quality guarantees to certain types of traffic is the special management of certain packets compared to the other. At this point the term Quality of Service (QoS) is introduced. A definition for QoS is: "the ability of a network element to provide a level of guarantee to a subset of traffic that ensures that the requirements of the service can be achieved with a defined (high) probability". In reality, the mechanisms of QoS do not provide larger network capacity or something similar, but they rather provide better network management so that it can be used more effectively and it can meet and address the requirements of the applications. In recent years, efforts have focused on providing quality of service at the network layer (Layer 3) so that it can be also applied on the Internet. Using architectures such as IntServ and DiffServ it is now possible to provide quality service at the network layer. However, the requirement for end-to-end QoS along with the expansion of networks towards switching equipment, creates the need for the application of QoS in the next lower layer, that is the data link layer (Layer 2). Hence, it should be borne in mind that the interoperability between the network and data link layers will lead to the provision of a single, transparent level of QoS. Based on the above, it becomes clear that in order to achieve end-to-end QoS, apart from the need for extension of the QoS to the data link layer there is also the need and requirement of interoperability with existing implementations in the network layer. In this direction, this dissertation focuses on studying the application of QoS to the data link layer. Furthermore, given the provision of quality of service to the IP layer, this dissertation considers the integration of QoS provision at Layer 2 and Layer 3. Therefore, the objective of this dissertation is twofold: a) QoS provision over Layer2-Ethernet networks and b) QoS provision over Layer 2 VPNs. For the implementation of Layer 2 QoS over Ethernet networks the IEEE 802.1p standard has been proposed. This standard has 3 bits length and is part of Tag Control Information field. During this dissertation performance tests were carried out on switches sorting traffic under CoS, which results in 8 different classes of traffic. Furthermore, queue configuration techniques on switches have been studied along with the cases of per port/per 802 .1q priorities and traffic classification. For the implementation of L2 QoS over VPNs there are techniques that are strongly related to the VPN type. This dissertation presents cases that L2 MPLS VPNs are used for the provisioning of either point-to-point (EoMPLS) or point-tomultipoint (VPLS) VPNs. In addition, research has been carried out for the extension of QoS provision over L2 MPLS VPNs to end-points that is purely L2 domain. The analysis at L2 domain was realized with the IEEE 802.1 p standard. Furthermore, the ability to provide QoS over multipoint L2 VPNs has been studied. Initially, the focus was on L3 devices (routers) and it was then extended to L2 using IEEE 802.1 p. Thus, the overall implementation was based on the combined use of 802.1p, DSCP and MPLS EXP. In addition, this dissertation presents methods, techniques and configurations of switches and routers that allow for the expansion of QoS from the network layer at a lower layer, thereby providing a consistent QoS level both at Layer 3 and Layer 2. Finally, the automated delivery/provision of these services in a real production network, GRNET, is presented. More specifically, the modeling of L2 QoS-enabled switches is described along with the automated configuration production for providing integrated QoS and issues related to the discovery, mapping and monitoring of QoS in switches using the SNMP protocol. The effectiveness of Layer 2 QoS mechanisms was tested and reinforced with experiments, which were conducted small scale at first in the lab and in the department of the University and then moved on to large scale at the production network of GRNET. The experiments showed that regardless of the expansion of a network towards Layer 2 devices, it is feasible to provide a unified QoS framework. All the above resulted in the provisioning of end-to-end QoS services at GRNET’s network.

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