Routing cost optimization in Multi Overlay Robust Networks

In the present work we solve the problem of data flow routing in Multi-Overlay Robust Networks (MORN) while aiming to minimize its routing cost. This kind of networks are typically IP/MPLS Data Network deployed over an SDH/DWDM transport infrastructure. Through the IP/MPLSMulti-Layer Data Network different kinds of services having a wide variety of quality of service requirements are delivered. Those services are being transported by an SDH/DWDM Transport Network which has different transport capacities. In this network, routing cost depends not only on the assigned transport capacity but also in the technology that it uses. Our problem seeks not only to route data flows through Data and Transport Networks but also to optimize routing costs and the reliability of the network. The inputs of our problem are the topology of the Data and Transport networks as well as the budget that the network operator has in order to improve its network routing costs and reliability. We will assume that the operator can only use that budget for installing new links between existing transport nodes. The output of the problem is the data flow routing in the Data and Transport Networks and its associated cost. Routing in the Transport Network is calculated not only in the nominal scenario - when all the Transport Network links are up and running - but also in each single transport link failure case.En el presente trabajo se resuelve el problema de rutear flujos de datos en una Red Multi- Capa Robusta (MORN por sus siglas en inglés), mientras que se trata de minimizar el costo asociado a su ruteo. Este tipo de redes son generalmente redes de datos IP/MPLS desplegadas sobre una infraestructura de transporte SDH/DWDM. Sobre la red de datos IP/MPLS se cursan distintos servicios con diferentes requerimientos de calidad de servicio (QoS). Los servicios de la Red de Datos son transportados por la red SDH/DWDM la cual tiene distintas capacidades de transporte. En éste tipo de redes el costo asociado al transporte depende no solo de la capacidad asignada para el transporte sino que también depende de la tecncología utilizada para transportar dicha capacidad. En el problema no sólo se busca enrutar flujos de datos a través de las Redes de Datos y Transporte sino que también se busca optimizar los costos de ruteo y la confiabilidad de la red. Como punto de partida, el problema toma como información la topología de las Redes de Datos y Transporte así como cierto presupuesto que el operador de la red posee para poder mejorar los costos de ruteo y la confiabilidad de su red. Asumiremos que dicho presupuesto solo puede ser utilizado para instalar nuevos enlaces entre los nodos existentes en la Red de Transporte. La salida del problema es el ruteo de los flujos de datos tanto en la Red de Datos como en la de Transporte, así como el costo asociado a dicho ruteo. El ruteo en la Red de Transporte se calcula no solo en el escenario nominal - cuando todos los enlaces de la Red de Transporte están funcionales - sino que también en cada escenario de falla simple en sus enlaces

Integer optimization applied to the design of robust minimum cost multi-layer networks.

In this work we solve the problem of designing an MPLS data network, to be deployed over an existing SDH/DWDM transport infrastructure, which is itself a combination of technologies. The data and different work hypothesis are from a particular operator: the National Telecommunications Administration (ANTEL) of Uruguay where the problem was originated. The target Data Network is an IP/MPLS Multi-Layer network over which different kinds of services are delivered and therefore with different quality requirements. During the process we will seek to minimize the economical resources incurred by the deployment over the Transport Infrastructure (Transport Network) of ANTEL. The solution found should be of optimal (minimum) cost and must be able to send a known traffic meeting certain quality parameters, even considering simple failures in some section of the Transport Network. The proposed problem is NP-Hard class in terms of computational complexity. Special cases of it are NP-complete problems. We model the problem algebraically as an Integer Mathematical Programming Problem and solve it approximately.En este trabajo se resuelve el problema de diseñar una red de datos MPLS, a ser desplegada sobre una infraestructura de transporte SDH/DWDM ya existente, que es a su vez una combinación de tecnologías. Los datos y las distintas hipótesis de trabajo son de un operador particular: la Agencia Nacional de Telecomunicaciones (ANTEL) de Uruguay, donde este problema fue originado. La Red de Datos objetivo es una red multi-capa IP/MPLS sobre la cual se distribuyen diferentes tipos de servicios que tiene distintos requerimientos de calidad. Durante el proceso se buscará minimizar los recursos económicos que surgen del despliegue sobre la infraestructura de transporte (Red de Transporte) de ANTEL. La solución encontrada debe ser de mínimo costo y debe poder enviar determinado tráfico cumpliendo con ciertos parámetros de calidad, incluso frente a fallas simples en la Red de Transporte. El problema propuesto es de la clase NP-Hard en términos de complejidad computacional. Casos particulares del mismo son problemas NP-Completos. Modelamos el problema de forma algebraica como un problema de Programación Entera y lo resolvemos de forma aproximada

Using GRASP and GA to design resilient and cost-effective IP/MPLS networks

The main objective of this thesis is to find good quality solutions for representative instances of the problem of designing a resilient and low cost IP/MPLS network, to be deployed over an existing optical transport network. This research is motivated by two complementary real-world application cases, which comprise the most important commercial and academic networks of Uruguay. To achieve this goal, we performed an exhaustive analysis of existing models and technologies. From all of them we took elements that were contrasted with the particular requirements of our counterparts. We highlight among these requirements, the need of getting solutions transparently implementable over a heterogeneous network environment, which limit us to use widely standardized features of related technologies. We decided to create new models more suitable to fit these needs. These models are intrinsically hard to solve (NP-Hard). Thus we developed metaheuristic based algorithms to find solutions to these real-world instances. Evolutionary Algorithms and Greedy Randomized Adaptive Search Procedures obtained the best results. As it usually happens, real-world planning problems are surrounded by uncertainty. Therefore, we have worked closely with our counterparts to reduce the fuzziness upon data to a set of representative cases. They were combined with different strategies of design to get to scenarios, which were translated into instances of these problems. Finally, the algorithms were fed with this information, and from their outcome we derived our results and conclusions

Journal of Telecommunications and Information Technology, 2004, nr 2

kwartalni

Optimal design of an IP/MPLS over DWDM network

Different approaches for deploying resilient optical networks of low cost constitute a traditional group of NP-Hard problems that have been widely studied. Most of them are based on the construction of low cost networks that fulfill connectivity constraints. However, recent trends to virtualize optical networks over the legacy fiber infrastructure, modified the nature of network design problems and turned inappropriate many of these models and algorithms. In this paper we study a design problem arising from the deployment of an IP/MPLS network over an existing DWDM infrastructure. Besides cost and resiliency, this problem integrates traffic and capacity constrains. We present: an integer programming formulation for the problem, theoretical results, and describe how several metaheuristics were applied in order to find good quality solutions, for a real application case of a telecommunications company

Optimal design of a Multi-Layer Network :An IP/MPLS over DWDMapplication case

In this paper we study a network design problem arising from the deployment of an IP/MPLS network over an existing transport infrastructure. The goal is to find a minimum cost installation of links such that traffic demands can resiliently be accomplished. We present an integer programming formulation for our problem and metaheuristics to find good quality solutions. This work is based on a real application case for a telecommunications compan

Nodal distribution strategies for designing an overlay network for long-term growth

Scope and Method of Study:This research looked at nodal distribution design issues associated with building an overlay network on top of an existing legacy network with overlay network switches and links not necessarily matching the switch and link locations of the underlying network. A mathematical model with two basic components, switch costs and link costs, was developed for defining the total cost of a network overlay. The nature of the underlying legacy topology determines the dominant factor, link or switch costs to the total cost function as well as the unit cost for switches and links.Findings and Conclusions:The three design heuristics presented first, locate overlay switches at nodes in the center of the legacy network as opposed to the periphery; second, locate overlay switches at legacy nodes with high connectivity; and third, locate overlay switches at legacy nodes with high traffic flow demands, can be used to help point to the direction of keeping costs under control when design changes are required. Applying the concept of efficient frontiers to the world of network design and building a suite of best designs gives the network designer greater insight into how to design the best network in the face of changing real-world constraints. For the cost model and the case studies evaluated using the design strategies in this study, distributed approaches generally tend to be a good choice when the link costs dominate the total cost function because total path distances and therefore link costs need to be minimized in preference over switch costs. A distributed overlay tends to have lower link costs because there is usually a greater probability that total path distances can be minimized because of greater connectivity. More connections set up the potential for more traffic flow path choices allowing each traffic flow to be sent along shorter paths. In legacy network topology designs that have many nodes with high connectivity, the overlay link costs can be relatively similar between designs and the switch costs can have a large impact upon total cost

SDN-based traffic engineering in data centers, Interconnects, and Carrier Networks

Server virtualization and cloud computing have escalated the bandwidth and performance demands on the DCN (data center network). The main challenges in DCN are maximizing network utilization and ensuring fault tolerance to address multiple node-and-link failures. A multitenant and highly dynamic virtualized environment consists of a large number of endstations, leading to a very large number of flows that challenge the scalability of a solution to network throughput maximization. The challenges are scalability, in terms of address learning, forwarding decision convergence, and forwarding state size, as well as flexibility for offloading with VM migration. Geographically distributed data centers are inter-connected through service providers’ carrier network. Service providers offer wide-area network (WAN) connection such as private lines and MPLS circuits between edges of data centers. DC sides of network operators try to maximize the utilization of such defined overlay WAN connection i.e. data center interconnection (DCI), which applies to edges of DC networks. Service provider sides of network operators try to optimize the core of carrier network. Along with the increasing adoption of ROADM, OTN, and packet switching technologies, traditional two-layer IP/MPLS-over-WDM network has evolved into three-layer IP/MPLS-over-OTN-over-DWDM network and once defined overlay topology is now transitioning to dynamic topologies based on on-demand traffic demands. Network operations are thus divided into three physical sub-networks: DCN, overlay DCI, and multi-layer carrier network. Server virtualization, cloud computing and evolving multilayer carrier network challenge traffic engineering to maximize utilization on all physical subnetworks. The emerging software-defined networking (SDN) architecture moves path computation towards a centralized controller, which has global visibility. Carriers indicate a strong preference for SDN to be interoperable between multiple vendors in heterogeneous transport networks. SDN is a natural way to create a unified control plane across multiple administrative divisions. This thesis contributes SDN-based traffic engineering techniques for maximizing network utilization of DCN, DCI, and carrier network. The first part of the thesis focuses on DCN traffic engineering. Traditional forwarding mechanisms using a single path are not able to take advantages of available multiple physical paths. The state-of-the-art MPTCP (Multipath Transmission Control Protocol) solution uses multiple randomly selected paths, but cannot give total aggregated capacity. Moreover, it works as a TCP process, and so does not support other protocols like UDP. To address these issues, this thesis presents a solution using adaptive multipath routing in a Layer-2 network with static (capacity and latency) metrics, which adapts link and path failures. This solution provides innetwork aggregated path capacity to individual flows, as well as scalability and multitenancy, by separating end-station services from the provider’s network. The results demonstrate an improvement of 14% in the worst bisection bandwidth utilization, compared to the MPTCP with 5 sub-flows. The second part of the thesis focuses on DCI traffic engineering. The existing approaches to reservation services provide limited reservation capabilities, e.g. limited connections over links returned by the traceroute over traditional IP-based networks. Moreover, most existing approaches do not address fault tolerance in the event of node or link failures. To address these issues, this thesis presents ECMP-like multipath routing algorithm and forwarding assignment scheme that increase reservation acceptance rate compared to state-of-art reservation frameworks in the WAN-links between data centers, and such reservations can be configured with a limited number of static forwarding rules on switches. Our prototype provides the RESTful web service interface for link-fail event management and re-routes paths for all the affected reservations. In the final part of the thesis, we focused on multi-layer carrier network traffic engineering. New dynamic traffic trends in upper layers (e.g. IP routing) require dynamic configuration of the optical transport to re-direct the traffic, and this in turn requires an integration of multiple administrative control layers. When multiple bandwidth path requests come from different nodes in different layers, a distributed sequential computation cannot optimize the entire network. Most prior research has focused on the two-layer problem, and recent three-layer research studies are limited to the capacity dimensioning problem. In this thesis, we present an optimization model with MILP formulation for dynamic traffic in a three-layer network, especially taking into account the unique technological constraints of the distinct OTN layer. Our experimental results show how unit cost values of different layers affect network cost and parameters in the presence of multiple sets of traffic loads. We also demonstrate the effectiveness of our proposed heuristic approach

Design and protection algorithms for path level aggregation of traffic in WDM metro optical networks

Wavelength Division Multiplexing (WDM) promises to offer a cost effective and scalable solution to meet the emerging demands of the Internet. WDM splits the tremendous bandwidth latent in a fiber into multiple non-overlapping wavelength channels, each of which can be operated at the peak electronic rate. Commercial systems with 128 wavelengths and transmission rates of up to 40 Gbps per wavelength have been made possible using state of the art optical technologies to deal with physical impairments. Systems with higher capacities are likely to evolve in the future. The end user requirements for bandwidth, on the other hand, have been ranging from 155 Mbps to 2.5 Gbps. Dedicating a wavelength for each end user will lead to severe underutilization of WDM channels. This brings to forefront the requirement for sharing of bandwidth in a wavelength among multiple end users.;The concept of wavelength sharing among multiple clients is called grooming. Grooming can be done purely at the optical layer (optical grooming) or it can be done with support from the client layer (electronic grooming). The advantage of all optical grooming is the ease of scalability due to its transparency as opposed to electronic grooming which is constrained by electronic bottlenecks. Efforts towards enhancing optical grooming is pursued through increasing optical switching speeds. However, technologies to make optical switches with high speeds, large port counts and low insertion losses have been elusive and may continue to remain so in the near future.;Recently, there have been some research into designing new architectures and protocols focused on optical grooming without resorting to fast optical switching. Typically, this is achieved in three steps: (1) configure the circuit in the form of a path or a tree; (2) use optical devices like couplers or splitters to allow multiple transmitters and/or receivers to share the same circuit; and (3) provide an arbitration mechanism to avoid contention among end users of the circuit. This transparent sharing of the wavelength channel utilizes the network resources better than the conventional low-speed circuit switched approaches. Consequently, it becomes important to quantify the improvement in achieved performance and evaluate if the reaped benefits justify the cost of the required additional hardware and software.;The contribution of this thesis is two fold: (1) developing a new architecture called light-trails as an IP based solution for next generation WDM optical networks, and (2) designing a unified framework to model Path Level Aggregation of Traffic in metrO Optical Networks (PLATOONs). The algorithms suggested here have three features: (1) accounts for four different path level aggregation strategies---namely, point to point (for example, lightpaths), point to multi-point (for example, source based light-trails), multi-point to point (for example, destination based light-trails) and multi-point to multi-point (for example, light-trails); (2) incorporates heterogenous switching architectures; and (3) accommodates multi-rate traffic. Algorithms for network design and survivability are developed for PLATOONs in the presence of both static and dynamic traffic. Connection level dedicated/shared, segregated/mixed protection schemes are formulated for single link failures in the presence of static and dynamic traffic. A simple medium access control protocol that avoids collisions when the channel is shared by multiple clients is also proposed.;Based on extensive simulations, we conclude that, for the studied scenarios, (1) when client layer has no electronic grooming capabilities, light-trails (employing multi-point to multi-point aggregation strategy) perform several orders of magnitude better than lightpaths and (2) when client layer has full electronic grooming capabilities, source based light-trails (employing point to multi-point aggregation strategy) perform the best in wavelength limited scenarios and lightpaths perform the best in transceiver limited scenarios.;The algorithms that are developed here will be helpful in designing optical networks that deploy path level aggregation strategies. The proposed ideas will impact the design of transparent, high-speed all-optical networks.</p