Talcott, Carolyn

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2012 - 20132
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  • Publication
    Reduction-Based Formal Analysis of BGP Instances
    (2012-01-01) Wang, Anduo; Talcott, Carolyn; Gurney, Alexander JT; Loo, Boon Thau; Scedrov, Andre
    Today’s Internet interdomain routing protocol, the Border Gateway Protocol (BGP), is increasingly complicated and fragile due to policy misconfigurations by individual autonomous systems (ASes). These misconfigurations are often difficult to manually diagnose beyond a small number of nodes due to the state explosion problem. To aid the diagnosis of potential anomalies, researchers have developed various formal models and analysis tools. However, these techniques do not scale well or do not cover the full set of anomalies. Current techniques use oversimplified BGP models that capture either anomalies within or across ASes, but not the interactions between the two. To address these limitations, we propose a novel approach that reduces network size prior to analysis, while preserving crucial BGP correctness properties. Using Maude, we have developed a toolkit that takes as input a network instance consisting of ASes and their policy configurations, and then performs formal analysis on the reduced instance for safety (protocol convergence). Our results show that our reduction based analysis allows us to analyze significantly larger network instances at low reduction overhead.
  • Publication
    A Reduction-Based Approach Towards Scaling Up Formal Analysis of Internet Configurations
    (2013-01-01) Wang, Anduo; Gurney, Alexander JT; Han, Xianglong; Cao, Jinyan; Loo, Boon T; Talcott, Carolyn; Scedrov, Andre
    The Border Gateway Protocol (BGP) is the single inter-domain routing protocol that enables network operators within each autonomous system (AS) to influence routing decisions by independently setting local policies on route filtering and selection. This independence leads to fragile networking and makes analysis of policy configurations very complex. To aid the systematic and efficient study of the policy configuration space, this paper presents network reduction, a scalability technique for policy-based routing systems. In network reduction, we provide two types of reduction rules that transform policy configurations by merging duplicate and complementary router configurations to simplify analysis. We show that the reductions are sound, dual of each other and are locally complete. The reductions are also computationally attractive, requiring only local configuration information and modification. We have developed a prototype of network reduction and demonstrated that it is applicable on various BGP systems and enables significant savings in analysis time. In addition to making possible safety analysis on large networks that would otherwise not complete within reasonable time, network reduction is also a useful tool for discovering possible redundancies in BGP systems.