Guérin, Roch A
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Publication Reliable Interdomain Routing Through Multiple Complementary Routing Processes(2008-10-15) Liao, Yong; Gao, Lixin; Guérin, Roch A; Zhang, Zhi-LiThe Internet inter-domain routing protocol, BGP, experiences frequent routing disruptions such as transient routing loops or loss of connectivity. The goal of this paper is to address this issue while preserving BGP’s benefits in terms of operational maturity and flexibility in accommodating diverse policies. In realizing this goal, we apply to inter-domain routing a common concept in the design of highly reliable systems, namely, the use of redundancy, which we introduce in a manner that maximizes compatibility with the existing BGP protocol. The basic idea is to run several, mostly unchanged BGP processes that compute complementary routes, so that in the presence of network instabilities a working path remains available to any destination. The paper outlines the design of this approach and compares it to previously proposed alternatives. The benefits of the scheme are demonstrated using actual BGP data and realistic simulations.Publication Modeling the dynamics of network technology adoption and the role of converters(2009-06-22) Sen, Soumya; Guérin, Roch; Hosanagar, Kartik; Jin, YoungmiNew network technologies constantly seek to displace incumbents. Their success depends on technological superiority, the size of the incumbent's installed base, users' adoption behaviors, and various other factors. The goal of this paper is to develop an understanding of competition between network technologies, and identify the extent to which different factors, in particular converters (a.k.a. gateways), affect the outcome. Converters can help entrants overcome the influence of the incumbent's installed base by enabling cross-technology inter-operability. However, they have development, deployment, and operations costs, and can introduce performance degradations and functionality limitations, so that if, when, why, and how they help is often unclear. To this end, the paper proposes and solves a model for adoption of competing network technologies by individual users. The model incorporates a simple utility function that captures key aspects of users' adoption decisions. Its solution reveals a number of interesting and at times unexpected behaviors, including the possibility for converters to reduce overall market penetration of the technologies and to prevent convergence to a stable state; something that never arises in their absence. The findings were tested for robustness, e.g., different utility functions and adoption models, and found to remain valid across a broad range of scenarios.Publication Functionality-rich Versus Minimalist Platforms: A Two-sided Market Analysis(2011-07-24) Sen, Soumya; Guérin, Roch A; Hosanagar, KartikShould a new ``platform'' target a functionality-rich but complex andexpensive design or instead opt for a bare-bone but cheaper one? This is afundamental question with profound implications for the eventual success ofany platform. A general answer is, however, elusive as it involves a complextrade-off between benefits and costs. The intent of this paper is tointroduce an approach based on standard tools from the fields of marketing andeconomics, which can offer some insight into this difficult question. Wedemonstrate its applicability by developing and solving a generic model thatincorporates key interactions between platform stakeholders. The solutionconfirms that the ``optimal'' number of features a platform should offerstrongly depends on variations in cost factors. More interestingly, it revealsa high sensitivity to small relative changes in those costs. The paper'scontribution and motivation are in establishing the potential of such across-disciplinary approach for providing qualitative and quantitativeinsights into the complex question of platform design.Publication Migrating the Internet to IPv6: An Exploration of the When and Why(2015-02-24) Nikkhah, Mehdi; Guerin, RochThe paper documents and to some extent elucidates the progress of IPv6 across major Internet stakeholders since its introduction in the mid 90’s. IPv6 offered an early solution to a well-understood and well-documented problem IPv4 was expected to encounter. In spite of early standardization and awareness of the issue, the Internet’s march to IPv6 has been anything but smooth, even if recent data point to an improvement. The paper documents this progression for several key Internet stakeholders using available measurement data, and identifies changes in the IPv6 ecosystem that may be in part responsible for how it has unfolded. The paper also develops a stylized model of IPv6 adoption across those stakeholders, and validates its qualitative predictive ability by comparing it to measurement data.Publication Always Acyclic Distributed Path Computation(2008-05-20) Guérin, Roch A; Ray, Saikat; Kwong, Kin-Wah (Eric); Sofia, RuteDistributed routing algorithms may give rise to transient loops during path recomputation, which can pose significant stability problems in high-speed networks. We present a new algorithm, Distributed Path Computation with Intermediate Variables (DIV), which can be combined with any distributed routing algorithm to guarantee that the directed graph induced by the routing decisions remains acyclic at all times. The key contribution of DIV, besides its ability to operate with any routing algorithm, is an update mechanism using simple message exchanges between neighboring nodes that guarantees loop-freedom at all times. DIV provably outperforms existing loop-prevention algorithms in several key metrics such as frequency of synchronous updates and the ability to maintain paths during transitions. Simulation results quantifying these gains in the context of shortest path routing are presented. In addition, DIV's universal applicability is illustrated by studying its use with a routing that operates according to a non-shortest path objective. Specifically, the routing seeks robustness against failures by maximizing the number of next-hops available at each node for each destination.Publication On the Feasibility and Efficacy of Protection Routing in IP Networks(2009-12-10) Kwong, Kin-Wah (Eric); Guérin, Roch A; Gao, Lixin; Zhang, Zhi-LiWith network components increasingly reliable, routing is playing an ever greater role in determining network reliability. This has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. Centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. However, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. This paper leverages the flexibility afforded by centralized routing to address these challenges. Specifically, we explore when and how standby backup forwarding options can be activated, while waiting for an update from the centralized server after the failure of an individual component (link or node). We provide analytical insight into the feasibility of such backups as a function of network structure, and quantify their computational complexity. We also develop an efficient heuristic reconciling protectability and performance, and demonstrate its effectiveness in a broad range of scenarios. The results should facilitate deployments of centralized routing solutions.Publication Improving VoIP Quality Through Path Switching(2005-03-13) Tao, Shu; Xu, Kuai; Estepa, Antonio; Fei, Teng; Gao, Lixin; Guérin, Roch A; Kurose, Jim; Towsley, Don; Zhang, Zhi-LiThe current best-effort Internet cannot readily provide the service guarantees that VoIP applications often require. Path switching can potentially address this problem without requiring new network mechanisms, simply by leveraging the robustness to performance variations available from connectivity options such as multi-homing and overlays. In this paper, we evaluate the effectiveness and benefits of path switching in improving the quality of VoIP applications, and demonstrate its feasibility through the design and implementation of a prototype gateway. We argue for an application-driven path switching system that accounts for both network path characteristics and application-specific factors (e.g., codec algorithms, playout buffering schemes). We also develop an application path quality estimator based on the ITU-T E-model for voice quality assessment, and an application-driven path switching algorithm that dynamically adapts the time scales over which path switching decisions are made to maximize voice quality. Through network emulation and experiments over a wide-area multi-homed testbed, we show that, with sufficient path diversity, path switching can yield meaningful improvements in voice quality. Hence by exploiting the inherent path diversity of the Internet, application-driven path switching is a viable option in providing quality-of-service to applications.Publication Application-Specific Path Switching: A Case Study for Streaming Video(2004-10-10) Tao, Shu; Guérin, Roch AThe focus of this paper is on improving the quality of streaming video transmitted over the Internet. The approach we investigate assumes the availability of multiple paths between the source and the destination, and dynamically selects the best one. Although this is not a new concept, our contribution is in estimating the "goodness" of a path from the perspective of the video stream, instead of relying only on raw network performance measures. The paper starts by showing that the use of raw network performance data to control path switching decisions can often result in poor choices from an application perspective, and then proceeds to develop a practical approach for evaluating, in real-time, the performance of different paths in terms of video quality. Those estimates are used to continuously select the path that yields the best possible transmission conditions for video streaming applications. We demonstrate the feasibility and performance of the scheme through experiments involving different types of videos.Publication Achieving Near-Optimal Traffic Engineering Solutions for Current OSPF/IS-IS Networks(2005-04-01) Sridharan, Ashwin; Guérin, Roch A; Diot, ChristopheTraffic engineering is aimed at distributing traffic so as to "optimize" a given performance criterion. The ability to carry out such an optimal distribution depends on the routing protocol and the forwarding mechanisms in use in the network. In IP networks running the OSPF or IS-IS protocols, routing is along shortest paths, and forwarding mechanisms are constrained to distributing traffic "uniformly" over equal cost shortest paths. These constraints often make achieving an optimal distribution of traffic impossible. In this paper, we propose and evaluate an approach that is capable of realizing near optimal traffic distribution without any change to existing routing protocols and forwarding mechanisms. In addition, we explore the trade-off that exists between performance and the overhead associated with the additional configuration steps that our solution requires. The paper's contributions are in formulating and evaluating an approach to traffic engineering for existing IP networks that achieves performance levels comparable to that offered when deploying other forwarding technologies such as MPLS.Publication Exploring the Performance Benefits of End-to-End Path Switching(2004-10-05) Tao, Shu; Xu, Kuai; Xu, Ying; Fei, Teng; Gao, Lixin; Guérin, Roch A; Kurose, Jim; Towsley, Don; Zhang, Zhi-LiThis paper explores the feasibility of improving the performance of end-to-end data transfers between different sites through path switching. Our study is focused on both the logic that controls path switching decisions and the configurations required to achieve sufficient path diversity. Specifically, we investigate two common approaches offering path diversity – multi-homing and overlay networks – and investigate their characteristics in the context of a representative wide-area testbed. We explore the end-to-end delay and loss characteristics of different paths and find that substantial improvements can potentially be achived by path switching, especially in lowering end-to-end losses. Based on this assessment, we develop a simple path-switching mechanism capable of realizing those performance improvements. Our experimental study demonstrates that substantial performance improvements are indeed achievable using this approach.