Abstract

Date of Conference: 29-31 May 2007 Conference Name: 11th International IFIP TC6 Conference, ONDM 2007 We propose an online traffic engineering (TE) scheme for efficient routing of bandwidth guaranteed connections on a Multiprotocol label switching (MPLS)/wavelength division multiplexing (WDM) network with a traffic pattern varying with the time of day. We first consider the problem of designing the WDM virtual topology utilizing multi-hour statistical traffic pattern. After presenting an effective solution to this offline problem, we introduce a Dynamic tRaffic Engineering AlgorithM (DREAM) that makes use of the bandwidth update and rerouting of the label switched paths (LSPs). The performance of DREAM is compared with commonly used online TE schemes and it is shown to be superior in terms of blocked traffic ratio. Document type: Part of book or chapter of book

Abstract

Multi-Protocol Label Switching (MPLS) provides ways to control the Label Switched Paths (LSPs) followed by traffic trunks in a network and thereby to better traffic engineer it. In this context, we look at the problem of organizing the mapping of LSPs in an optimal way throughout the network on the basis of a given objective function. This problem is highly combinatorial and makes dynamic and real-time features a difficult issue for any LSP routing scheme. For this reason, we propose a computationally efficient, though approximate, on-line scheme adapted to an incremental optimization of the network state. It is then applied to a seldom mentioned traffic engineering problem: the compromise between load-balancing and traffic minimization. It is expected that clever routing strategies to balance the network load will sometimes favor longer paths in order to avoid congestion, leading to an increase of the overall network utilization. This reasoning is confirmed by our study, and we show that an improvement in network management can be made by appropriately tuning this compromise. Peer reviewed

Abstract

O surgimento de novas aplicações na Internet, tais como voz sobre IP (VoIP), ensino a distância interativo, realidade virtual, videoconferência, etc, impõe a necessidade de garantias de qualidade de serviço (QoS - Quality of Service) fim-a-fim. Tais aplicações exigem limites no atraso, sua variação (jitter) e nas perdas de pacotes. O modelo de serviço atual da Internet não possibilita a obtenção dos requisitos de QoS mencionados. Assim sendo, o modelo DifIServ quando combinado com a engenharia de tráfego, provida pelo MPLS pode fornecer uma arquitetura apropriada para assegurar garantias de QoS às aplicações. Neste trabalho, considera-se um ambiente de rede, onde os tráfegos multimídia oriundos de um ISP local são classificados na borda da rede backbone em sub-classes de tráfego definidas pelo DiffServ. Em seguida, estes tráfegos são mapeados em diferentes LSPs (Labei Swiched Paths) com diferentes características de vazão, atraso e jitter. Por meio de modelagem e simulação demonstra-se que o MPLS com a Engenharia de Tráfego combinado com o DiffServ garante os limites requeridos pelas aplicações multimídia para os parâmetros de tráfego e de QoS. Currently, the Internet provides only best-effort Service that treats packets equally, and recently new kinds of distributed applications, like Internet telephony, video conferencing, video-on-demand have been developed which are sensitive to the end-to-end Quality of Service (QoS) received from the network. Such applications demand limits in the de-lay, jitter and packet loss. The DiffServ model when combined with Traffic Engineering can provide a suitable architecture for ensuring end-to-end QoS guarantees to several kinds of applications. MPLS is emerging to be the choice for the core network applying multi-service networks, and providing Traffic Engineering. In this work, the following environment is considered: in the network edge, the packets are classified in sub-classes of traffic defined by the DiffServ, with different types of delay, jitter and throughput characteristics. In the MPLS backbone, these sub-classes of traffic are mapped in the different Labei Switched Paths (LSPs). This work proposes to show through modelling and simulation, Traffic Engineering over MPLS combined with DiffServ guarantees, the limits required by multimedia applications to the parameters of traffic and QoS. Dissertação (Mestrado) Document type: Doctoral thesis

Abstract

During the last years, MultiProtocol Label Switching (MPLS) has been deployed by most large Service Providers (SP). The main driver for MPLS deployment is the ability to provide new services with stringent Service Level Agreements (SLAs) such as layer-2 and layer-3 Virtual Private Networks (VPNs) as well as Voice and Video over IP. Most of these services are already deployed inside single SP networks. However, customers now require world-wide VPN and VoIP services. Therefore, SPs need to collaborate to offer these services across multiple SP networks. Inside a single SP network, each node usually knows the complete topology of the network with the load and delay of all the links. Based on this information, each router is able to compute constrained paths toward any other router inside the SP network. Then, it can establish a connection and reserve resources along the computed path with the Resource reSerVation Protocol (RSVP-TE). However, when services with stringent requirements must cross multiple SP networks the computation of the path becomes a problem. Routers in different SP networks exchange routing information by using the Border Gateway Protocol (BGP). BGP provides reachability information. It does not distribute complete topology, delay and bandwidth information. One way to provide guaranteed services crossing different SPs is to delegate the computation of the paths to a Path Computation Element (PCE) that learns the topology of the different SPs. However, this requires that SPs reveal information that they usually consider confidential, their topology. In this thesis, we perform active measurements to show the difficulty to engineer the interdomain traffic with BGP. MPLS together with RSVP-TE provide much more control on the traffic. We define extensions to RSVP-TE for the protection of inter-AS MPLS paths. The aim is to be able to provide the same service guarantees as inside a domain while keeping the internal topology of SPs confidential, as required by SPs. We propose and evaluate distributed techniques relying on PCEs for the computation of interdomain constrained paths respecting the latter confidentiality requirement. (FSA 3)--UCL, 2006

Abstract

With the increasing usage of QoS-based applications, traffic engineering in communication networks has become more crucial. For the optimal utilization of network resources, service providers need to consider multiple criteria that can be customer- or traffic-oriented. Multiprotocol Label Switching (MPLS) has been developed to apply more convenient traffic engineering in autonomous systems. This thesis focuses on the multiobjective optimization of Label Switched Path design problem in MPLS networks. Minimal routing cost, optimal load-balance in the network, and minimal splitting of traffic form the objectives. The problem is formulated as a zero-one mixed integer program and aims at exploring the trade-offs among the objectives. The integer constraints make the problem NP-hard. In the thesis first both the exact and heuristic multiobjective optimization approaches are discussed, and then a heuristic framework based on simulated annealing is developed. Various search strategies within the framework are investigated and experimental studies are carried out for a performance comparison.

Abstract

The expectations of every user of today’s internet is becoming relatively high more especially as the internet applications are becoming steadily sensitive to time and delays. The critical nature of some of these applications is more apparent now that they are real-time. These pose a whole lot of challenges to network operators and service providers because they will not only need to provide these services to users but also ensure that these services rendered meet up to quality expectations and standards. It is therefore very necessary and important for them to provide good quality of service with appreciable good performance at no incurable costs- that is while maximizing revenue- to them. A need therefore arises for the adoption of a scalable method or tool for meeting up to these challenges. Multi-Protocol Label Switching (MPLS) stands out to be the choicest tool and key for providing these requirements because of its traffic engineering (TE) capability in IP network and as such the internet needs to be equipped with this all-embracing technology. This report presents the performance analysis of this technology (MPLS TE) vis-à-vis the traditional IP with respect to the average throughput, Quality of service rendered, delay suffered and minimization of congestions or traffic overflow in a bid to seeing how and why MPLS is more capable in optimizing traffic applications when adopted by service providers and network operators. And from the conclusion of the analysis and results it would have been established that MPLS appeared to be more capable in the optimization of traffic applications with respect to the above characteristics when compared with the traditional IP.

Abstract

nkara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2010. Thesis (Ph. D.) -- Bilkent University, 2010. Includes bibliographical references leaves 153-165. We study Traffic Engineering (TE) in Multiprotocol Label Switching (MPLS)/Wavelength Division Multiplexing (WDM) networks and propose a multi-layer TE method. MPLS provides powerful TE features for IP networks and is widely deployed in backbone networks. WDM can increase the transmission capacity of optical fibers to tremendous amounts, therefore it has been the dominant multiplexing technology used in the optical layer. The proposed multi-layer TE solution facilitates efficient use of network resources where the TE mechanisms in the MPLS and WDM layers coordinate. We consider a static WDM layer and available traffic expectation information. The TE problem arising in the considered scenario is the Virtual Topology Design (VTD) problem, which involves the decision of WDM lightpaths to be established, calculation of MPLS Label Switched Paths (LSPs) on the resulting virtual topology, and calculation of the routes and wavelengths in the physical topology that correspond to the lightpaths in the virtual topology. We assume a daily traffic pattern changing with the time of day and aim to design a static virtual topology that satisfies as much of the offered traffic as possible, over the whole day. In our proposed solution, the multi-layer VTD problem is solved by decomposing it into two sub-problems, each involving in a single layer. The decomposition approach is used in the thesis due to the huge computational burden of the combined solution for real-life networks. The sub-problem in the MPLS layer is the design of the lightpath topology and calculation of the LSP routes on this virtual topology. This problem is known to be NP-complete and finding its optimum solution is possible only for small networks. We propose a Tabu Search based heuristic method to solve two versions of this problem, resource oriented and performance oriented. Integer Linear Programming (ILP) relaxations are also developed for obtaining upper and lower bounds. We show that the gap between the produced solutions and the lower and upper bounds are around 10% and 7% for the resource and performance oriented problems, respectively. Since the actual traffic can show deviations from the expected values, we also developed an MPLS layer online TE method to compensate the instantaneous fluctuations of the traffic flows. In the proposed method, the LSPs are rerouted dynamically using a specially designed cost function. Our numerical studies show that using the designed cost function results in much lower blockings than using commonly used Widest Shortest Path First and Available Shortest Path First approaches in the literature. The corresponding sub-problem of the multi-layer VTD problem in the WDM layer is the Static Lightpath Establishment (SLE) problem. Along with the capacity and wavelength continuity constraints, we also consider the Bit Error Rate (BER) constraints due to physical layer impairments such as attenuation, polarization mode dispersion and switch crosstalk. This problem is NP-complete even without the BER constraints. We propose a heuristic solution method and develop an exact ILP formulation to evaluate the performance of the proposed method for small problem sizes. Our proposed method produces solutions close to the optimum solutions for the cases in which the ILP formulation could be solved to optimality. Then, these solution methods for the single layer sub-problems are combined in a multi-layer TE scheme to solve the VTD problem in both layers jointly. The proposed TE scheme considers the physical layer limitations and optical impairments. This TE scheme can be applied by keeping each layer’s information hidden from the other layer, but our simulations show that it can produce more effective and efficient solutions when the physical layer topology information is shared with the MPLS layer. We also investigate the effect of non-uniform optical components in terms of impairment characteristics. The numerical results show that more traffic can be routed when all the components in the network have moderate impairment characteristics, compared to the case in which some components have better and some have worse impairment characteristics. Şengezer, Namık Ph.D.

Abstract

The principle of load balancing is to distribute the data load more evenly over the network in order to increase the network performance and efficiency. With dynamic load balancing the routing is undated at certain intervals. This thesis was developed to evaluate load balancing methods in the IP-network of TeliaSonera.Load balancing using short path routing, bottleneck load balancing and load balancing using MPLS have been evaluated. Short path routing is a flow sharing technique that allows routing on paths other than the shortest one. Load balancing using short path routing is achieved by dynamic updates of the link weights. Bottleneck is in its nature a dynamic load balancing algorithm. Unlike load balancing using short path routing it updates the flow sharing, not the metrics. The algorithm uses information about current flow sharing and link loads to detect bottlenecks within the network. The information is used to calculate new flow sharing parameters. When using MPLS, one or more complete routing paths (LSPs) are defined at each edge LSR before sending any traffic. MPLS brings the ability to perform flow sharing by defining the paths to be used and how the outgoing data load is to be shared among these. The model has been built from data about the network supplied by TeliaSonera. The model consists of a topology part, a traffic part, a routing part and cost part. The traffic model consists of a OD demand matrix. The OD demand matrix has been estimated from collected link loads. This was done with estimation models; the gravity model and an optimisation model. The algorithms have been analysed at several scenarios; normal network, core node failure, core link failure and DWDM system failure. A cost function, where the cost increases as the link load increases has been used to evaluate the algorithms. The signalling requirements for implementation of the load balancing algorithm have also been investigated.

Abstract

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University The wireless mesh network is a potential network for the future due to its excellent inherent characteristic for dynamic self-healing, self-configuration and self-organization. It also has the advantage of easy interoperability networking and the ability to form multi-linked ad-hoc networks. It has a decentralized topology, is cheap and highly scalable. Furthermore, its ease in deployment and easy maintenance are other inherent networking qualities. These aforementioned qualities of the wireless mesh network bring advantages to transmission capability of heterogeneous networks. However, transmissions in wireless mesh network create comparative performance based challenges such as congestion, load-balancing, scalability over increasing networks and coverage capacity. Consequently, these challenges and problems in the routing and switching of packets in the wireless mesh network routing protocols led to a proposal on the resolution of these failures with a combination algorithm and a management based security for the network and its transmitted packets. There are equally contentious services like reliability of the network and quality of service for real-time multimedia traffic flows with other challenges such as path computation and selection in the wireless mesh network. This thesis is therefore a cumulative proposal to the resolution of the outlined challenges and open research areas posed by using wireless mesh network routing protocol. It advances the resolution of these challenges in the mesh environment using a hybrid optimization – traffic engineering, to increase the effectiveness and the reliability of the network. It also proffers a cumulative resolution of the diverse contributions on wireless mesh network routing protocol and transmission. Adaptation and optimization are carried out on the wireless mesh network designed network using traffic engineering mechanism and technique. The research examines the patterns of mesh packet transmission and evaluates the challenges and failures in the mesh network packet transmission. It develops a solution based algorithm for resolutions and proposes the traffic engineering based solution.. These resultant performances and analysis are usually tested and compared over wireless mesh IEEE802.11n or other older proposed documented solution. This thesis used a carefully designed campus mesh network to show a comparative evaluation of an optimal performance of the mesh nodes and routers over a normal IEE802.11n based wireless domain network to show differentiation by optimization using the created algorithms. Furthermore, the indexes of performance being the metric are used to measure the utility and the reliability, including capacity and throughput at the destination during traffic engineered transmission. In addition, the security of these transmitted data and packets are optimized under a traffic engineered technique. Finally, this thesis offers an understanding to the security contribution using traffic engineering resolution to create a management algorithm for processing and computation of the wireless mesh networks security needs. The results of this thesis confirmed, completed and extended the existing predictions with real measurement.