The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform

Miguel Rocha - One of the best experts on this subject based on the ideXlab platform.

  • DCAI - Robust Optimization of Intradomain Routing Using Evolutionary Algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • robust optimization of Intradomain Routing using evolutionary algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • multiobjective evolutionary algorithms for Intradomain Routing optimization
    Congress on Evolutionary Computation, 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

  • IEEE Congress on Evolutionary Computation - Multiobjective Evolutionary Algorithms for Intradomain Routing optimization
    2011 IEEE Congress of Evolutionary Computation (CEC), 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

Paulo Cortez - One of the best experts on this subject based on the ideXlab platform.

  • DCAI - Robust Optimization of Intradomain Routing Using Evolutionary Algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • robust optimization of Intradomain Routing using evolutionary algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • multiobjective evolutionary algorithms for Intradomain Routing optimization
    Congress on Evolutionary Computation, 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

  • IEEE Congress on Evolutionary Computation - Multiobjective Evolutionary Algorithms for Intradomain Routing optimization
    2011 IEEE Congress of Evolutionary Computation (CEC), 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

Albert Greenberg - One of the best experts on this subject based on the ideXlab platform.

  • NSDI - OSPF monitoring: architecture, design and deployment experience
    2004
    Co-Authors: Aman Shaikh, Albert Greenberg
    Abstract:

    Improving IP control plane (Routing) robustness is critical to the creation of reliable and stable IP services. Yet very few tools exist for effective IP route monitoring and management. We describe the architecture, design and deployment of a monitoring system for OSPF, an IP Intradomain Routing protocol in wide use. The architecture has three components, separating the capture of raw LSAs (Link State Advertisements - OSPF updates), the real-time analysis of the LSA stream for problem detection, and the off-line analysis of OSPF behavior. By speaking "just enough" OSPF, the monitor gains full visibility of LSAs, while remaining totally passive and visible only at the point of attachment. We describe a methodology that allows efficient real-time detection of changes to the OSPF network topology, flapping network elements, LSA storms and anomalous behavior. The real-time analysis capabilities facilitate generation of alerts that operators can use to identify and troubleshoot problems. A flexible and efficient toolkit provides capabilities for off-line analysis of LSA archives. The toolkit enables post-mortem analysis of problems, what-if analysis that can aid in maintenance, planning, and deployment of new services, and overall understanding of OSPF behavior in large networks. We describe our experiences in deploying the OSPF monitor in a large operational ISP backbone and in a large enterprise network, as well as several examples that illustrate the effectiveness of the monitor in tracking changes to the network topology, equipment problems and Routing anomalies.

  • ospf monitoring architecture design and deployment experience
    Networked Systems Design and Implementation, 2004
    Co-Authors: Aman Shaikh, Albert Greenberg
    Abstract:

    Improving IP control plane (Routing) robustness is critical to the creation of reliable and stable IP services. Yet very few tools exist for effective IP route monitoring and management. We describe the architecture, design and deployment of a monitoring system for OSPF, an IP Intradomain Routing protocol in wide use. The architecture has three components, separating the capture of raw LSAs (Link State Advertisements - OSPF updates), the real-time analysis of the LSA stream for problem detection, and the off-line analysis of OSPF behavior. By speaking "just enough" OSPF, the monitor gains full visibility of LSAs, while remaining totally passive and visible only at the point of attachment. We describe a methodology that allows efficient real-time detection of changes to the OSPF network topology, flapping network elements, LSA storms and anomalous behavior. The real-time analysis capabilities facilitate generation of alerts that operators can use to identify and troubleshoot problems. A flexible and efficient toolkit provides capabilities for off-line analysis of LSA archives. The toolkit enables post-mortem analysis of problems, what-if analysis that can aid in maintenance, planning, and deployment of new services, and overall understanding of OSPF behavior in large networks. We describe our experiences in deploying the OSPF monitor in a large operational ISP backbone and in a large enterprise network, as well as several examples that illustrate the effectiveness of the monitor in tracking changes to the network topology, equipment problems and Routing anomalies.

  • netscope traffic engineering for ip networks
    IEEE Network, 2000
    Co-Authors: Anja Feldmann, Albert Greenberg, Carsten Lund, Nick Reingold, Jennifer Rexford
    Abstract:

    Managing large IP networks requires an understanding of the current traffic flows, Routing policies, and network configuration. However, the state of the art for managing IP networks involves manual configuration of each IP router, and traffic engineering based on limited measurements. The networking industry is sorely lacking in software systems that a large Internet service provider can use to support traffic measurement and network modeling, the underpinnings of effective traffic engineering. This article describes the AT&T Labs NetScope, a unified set of software tools for managing the performance of IP backbone networks. The key idea behind NetScope is to generate global views of the network on the basis of configuration and usage data associated with the individual network elements. Having created an appropriate global view, we are able to infer and visualize the networkwide implications of local changes in traffic, configuration, and control. Using NetScope, a network provider can experiment with changes in network configuration in a simulated environment rather than the operational network. In addition, the tool provides a sound framework for additional modules for network optimization and performance debugging. We demonstrate the capabilities of the tool through an example traffic engineering exercise of locating a heavily loaded link, identifying which traffic demands flow on the link, and changing the configuration of Intradomain Routing to reduce the congestion.

Pedro Sousa - One of the best experts on this subject based on the ideXlab platform.

  • DCAI - Robust Optimization of Intradomain Routing Using Evolutionary Algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • robust optimization of Intradomain Routing using evolutionary algorithms
    Distributed Computing and Artificial Intelligence, 2013
    Co-Authors: Vitor Manuel Sa Pereira, Paulo Cortez, Pedro Sousa, Miguel Rocha
    Abstract:

    Open Shortest Path First (OSPF) is a widely used Routing protocol that depends on weights assigned to each link to make Routing decisions. If traffic demands are known, the OSPF weight setting (OSPFWS) problem can be defined to seek a set of weights that optimize network performance, typically by minimizing a congestion measure. The OSPFWS problem is NP-hard and, thus, meta-heuristics such as Evolutionary Algorithms (EAs) have been used in previous work to obtain near optimal solutions. However, the dynamic nature of this problem leads to the necessity of addressing these problems in a more robust manner that can deal with changes in the conditions of the network. Here, we present EAs for two of those tasks, defining objective functions that take into account, on the one hand, changes in the traffic demand matrices and, on the other, single link failures. Those functions use weighting schemes to provide trade-offs between the behaviour of the network in distinct conditions, thus providing robust sets of OSPF weights.The algorithms are implemented in the open-source software NetOpt framework.

  • multiobjective evolutionary algorithms for Intradomain Routing optimization
    Congress on Evolutionary Computation, 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

  • IEEE Congress on Evolutionary Computation - Multiobjective Evolutionary Algorithms for Intradomain Routing optimization
    2011 IEEE Congress of Evolutionary Computation (CEC), 2011
    Co-Authors: Miguel Rocha, Tiago Sa, Pedro Sousa, Paulo Cortez
    Abstract:

    Evolutionary Algorithms (EAs) have been used to develop methods for Traffic Engineering (TE) over IP-based networks in the last few years, being used to reach the best set of link weights in the configuration of intra-domain Routing protocols, such as OSPF. In this work, the multiobjective nature of a class of optimization problems provided by TE with Quality of Service constraints is identified. Multiobjective EAs (MOEAs) are developed to tackle these tasks and their results are compared to previous approaches using single objective EAs. The effect of distinct genetic representations within the MOEAs is also explored. The results show that the MOEAs provide more flexible solutions for network management, but are in some cases unable to reach the level of quality obtained by single objective EAs. Furthermore, a freely available software application is described that allows the use of the mentioned optimization algorithms by network administrators, in an user-friendly way by providing adequate user interfaces for the main TE tasks.

Renata Teixeira - One of the best experts on this subject based on the ideXlab platform.

  • Network sensitivity to hot-potato disruptions
    Proceedings of the 2004 conference on Applications technologies architectures and protocols for computer communications - SIGCOMM '04, 2020
    Co-Authors: Renata Teixeira, Aman Shaikh, Tim Griffin, Geoffrey M Voelker
    Abstract:

    International audienceHot-potato Routing is a mechanism employed when there are multi-ple (equally good) interdomain routes available for a given destina-tion. In this scenario, the Border Gateway Protocol (BGP) selects the interdomain route associated with the closest egress point based upon Intradomain path costs. Consequently, Intradomain Routing changes can impact interdomain Routing and cause abrupt swings of external routes, which we call hot-potato disruptions. Recent work has shown that hot-potato disruptions can have a substantial impact on large ISP backbones and thereby jeopardize the network robust-ness. As a result, there is a need for guidelines and tools to assist in the design of networks that minimize hot-potato disruptions. How-ever, developing these tools is challenging due to the complex and subtle nature of the interactions between exterior and interior rout-ing. In this paper, we address these challenges using an analytic model of hot-potato Routing that incorporates metrics to evaluate network sensitivity to hot-potato disruptions. We then present a methodology for computing these metrics using measurements of real ISP networks. We demonstrate the utility of our model by an-alyzing the sensitivity of a large AS in a tier 1 ISP network

  • predicting critical Intradomain Routing events
    Global Communications Conference, 2010
    Co-Authors: Amelie Medem, Renata Teixeira, Nicolas Usunier
    Abstract:

    Network equipments generate an overwhelming number of reports and alarms every day, but only a small fraction of these alarms require the intervention of network operators. Our goal is to build a system to automatically select the set of critical alarms, so that network operators can focus their time and effort on these critical events. As a first step, we focus on alarms from Intradomain Routing. Our key observation is that operators already use trouble ticketing systems to record all events that require their intervention. Hence, we can use the history of trouble tickets combined with Intradomain Routing messages to train a classifier. Then, we can apply this classifier online to process Intradomain Routing messages and single out the critical events. This paper shows the feasibility of this approach by using the k-nearest neighbor algorithm to build classifiers from IS-IS and trouble ticket data from two networks. Our results show that we can accurately pinpoint approximately 70% of critical events for both networks.

  • GLOBECOM - Predicting Critical Intradomain Routing Events
    2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010
    Co-Authors: Amelie Medem, Renata Teixeira, Nicolas Usunier
    Abstract:

    Network equipments generate an overwhelming number of reports and alarms every day, but only a small fraction of these alarms require the intervention of network operators. Our goal is to build a system to automatically select the set of critical alarms, so that network operators can focus their time and effort on these critical events. As a first step, we focus on alarms from Intradomain Routing. Our key observation is that operators already use trouble ticketing systems to record all events that require their intervention. Hence, we can use the history of trouble tickets combined with Intradomain Routing messages to train a classifier. Then, we can apply this classifier online to process Intradomain Routing messages and single out the critical events. This paper shows the feasibility of this approach by using the k-nearest neighbor algorithm to build classifiers from IS-IS and trouble ticket data from two networks. Our results show that we can accurately pinpoint approximately 70% of critical events for both networks.

  • joint analysis of network incidents and Intradomain Routing changes
    Conference on Network and Service Management, 2010
    Co-Authors: Amelie Medem, Renata Teixeira, Nick Feamster, Mickael Meulle
    Abstract:

    This paper studies how Intradomain Routing instability relates to events in network trouble tickets for two networks: a VPN provider and the Internet2 backbone network. Our goal in performing this joint analysis of Routing and trouble tickets is to better understand the likely underlying causes of Intradomain Routing instability. We develop a method to correlate trouble tickets with instability events and find that, although unplanned events last longer than scheduled maintenance, there is no single underlying cause for most instability, and that these causes differ across networks. In comparison to a similar study from Labovitz et al. from ten years ago, we find that, while certain causes of instability such as maintenance and circuit problems remain significant, power issues have become much less prevalent, and software-related problems have become more common.

  • CNSM - Joint analysis of network incidents and Intradomain Routing changes
    2010 International Conference on Network and Service Management, 2010
    Co-Authors: Amelie Medem, Renata Teixeira, Nick Feamster, Mickael Meulle
    Abstract:

    This paper studies how Intradomain Routing instability relates to events in network trouble tickets for two networks: a VPN provider and the Internet2 backbone network. Our goal in performing this joint analysis of Routing and trouble tickets is to better understand the likely underlying causes of Intradomain Routing instability. We develop a method to correlate trouble tickets with instability events and find that, although unplanned events last longer than scheduled maintenance, there is no single underlying cause for most instability, and that these causes differ across networks. In comparison to a similar study from Labovitz et al. from ten years ago, we find that, while certain causes of instability such as maintenance and circuit problems remain significant, power issues have become much less prevalent, and software-related problems have become more common.