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Browsing by Author "Thompson, Christopher"

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    Part I Physical Modeling Of The Chippewa River - Mississippi River Confluence
    (St. Anthony Falls Laboratory, 1981-01) Song, Charles C. S.; Jaramillo, Carlos; Ottensmann, Peggy; Thompson, Christopher
    A physical model of the confluence of the Chippewa and Mississippi Rivers, 1 to 200 horizontal and I to 40 vertical scale ratios, was constructed and tested. Commercially available sand, having the mean diameter of 0.42 rom, was used as the bed material. with this bed material it was found necessary to distort the Froude number by a factor of 1.85 in order to simulate the sediment movement correctly. The model was successfully calibrated by reproducing the bed profile change which occurred in the field between the fall of 1977 and the spring of 1978. The model was tested for eight different conditions. Four runs were specifically devoted to measuring the velocity distribution, water surface profile, and the bed profile under steady flow conditions. Two r,uns were conducted to study the filling process of a dredge cut in the Mississippi River. A run was made to study the response of the river to an extreme condition~ a combination of a very wet year in the Chippewa River and a very dry year in the Mississippi River. The last run was for the study of the effect of a low head dam in the Chippewa River. This report describes the results of, these experimental runs and presents conclusions and recommendations.
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    Taking Routers Off Their Meds: Unstable Routers and the Buggy BGP Implementations That Cause Them
    (2011-11-30) Schuchard, Max; Thompson, Christopher; Hopper, Nicholas J.; Kim, Yongdae
    Both academic research and historical incidents have shown the impact of unstable BGP speakers on network performance and reliability. A large amount of time and energy has been invested improving router stability. In this paper, we show how an adversary in control of a BGP speaker in a transit AS can cause a victim router in an arbitrary location on the Internet to become unstable. Through experimentation with both hardware and software routers, we examine the behavior of routers under abnormal conditions and come to four conclusions. First, routers placed in certain states behave in anything but a stable manner. Second, unexpected but perfectly legal BGP messages can place routers into those states with disconcerting ease. Third, an adversary can use these messages to disrupt a victim router to which he is not directly connected. Fourth, modern best practices do little to prevent these attacks. These conclusions lead us to recommend more rigorous testing of BGP implementations, focusing as much on protocol correctness as software correctness.