A necessary and sufficient condition is given for the existence of prices that induce coordinatio... more A necessary and sufficient condition is given for the existence of prices that induce coordination in coupled linear dynamic systems. The condition is shown to be equivalent to the servomechanism controllability of an adjoint system.
For the engineering, operation and administration of switching systems, it is desirable to be abl... more For the engineering, operation and administration of switching systems, it is desirable to be able to quickly and accurately estimate the grade of service for different traffic loadings and for hypothetical scenarios and thus to be able to answer what-if questions. This paper presents a probabilistic model that meets this need for a class of overload controls in distributed switching systems. The model is modular and can capture the salient features of a variety of throttle and monitor designs. The model accurately calculates the probability a call is blocked given hypothetical traffic mixes, customer retry probabilities, load imbalances and load variations during the busy hour.
This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Expe... more This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Experience held in January 2016. This seminar was a followup of the seminar on Global Measurement Frameworks held in 2013, which focused on the development of global Internet measurement platforms and associated metrics. The second seminar aimed at discussing the practical experience gained with building these global Internet measurement platforms. It brought together people who are actively involved in the design and maintenance of global Internet measurement platforms and who do research on the data delivered by such platforms. Researchers in this seminar have used data derived from global Internet measurement platforms in order to manage networks or services or as input for regulatory decisions. The entire set of presentations delivered during the seminar is made publicly available at [1].
Proceedings of the ACM Internet Measurement Conference, 2020
This work presents a large-scale, longitudinal measurement study on the adoption of application u... more This work presents a large-scale, longitudinal measurement study on the adoption of application updates, enabling continuous reporting of potentially vulnerable software populations worldwide. Studying the factors impacting software currentness, we investigate and discuss the impact of the platform and its updating strategies on software currentness, device lock-in effects, as well as user behavior. Utilizing HTTP User-Agent strings from end-hosts, we introduce techniques to extract application and operating system information from myriad structures, infer version release dates of applications, and measure population adoption, at a global scale. To deal with loosely structured User-Agent data, we develop a semi-supervised method that can reliably extract application and version information for some 87% of requests served by a major CDN every day. Using this methodology, we track release and adoption dynamics of some 35,000 applications. Analyzing over three years of CDN logs, we sho...
This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Expe... more This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Experience held in January 2016. This seminar was a followup of the seminar on Global Measurement Frameworks held in 2013, which focused on the development of global Internet measurement platforms and associated metrics. The second seminar aimed at discussing the practical experience gained with building these global Internet measurement platforms. It brought together people who are actively involved in the design and maintenance of global Internet measurement platforms and who do research on the data delivered by such platforms. Researchers in this seminar have used data derived from global Internet measurement platforms in order to manage networks or services or as input for regulatory decisions. The entire set of presentations delivered during the seminar is made publicly available at [1].
Probability in the Engineering and Informational Sciences, 1995
Motivated by extreme-value engineering in service systems, we develop and evaluate simple approxi... more Motivated by extreme-value engineering in service systems, we develop and evaluate simple approximations for the distributions of maximum values of queueing processes over large time intervals. We provide approximations for several different processes, such as the waiting times of successive customers, the remaining workload at an arbitrary time, and the queue length at an arbitrary time, in a variety of models. All our approximations are based on extreme-value limit theorems. Our first approach is to approximate the queueing process by one-dimensional reflected Brownian motion (RBM). We then apply the extremevalue limit for RBM, which we derive here. Our second approach starts from exponential asymptotics for the tail of the steady-state distribution. We obtain an approximation by relating the given process to an associated sequence of i.i.d. random variables with the same asymptotic exponential tail. We use estimates of the asymptotic variance of the queueing process to determine ...
Journal of Applied Mathematics and Stochastic Analysis, 1994
An open-loop window flow-control scheme regulates the flow into a system by allowing at most a sp... more An open-loop window flow-control scheme regulates the flow into a system by allowing at most a specified window size W of flow in any interval of length L. The sliding window considers all subintervals of length L, while the jumping window considers consecutive disjoint intervals of length L. To better understand how these window control schemes perform for stationary sources, we describe for a large class of stochastic input processes the asymptotic behavior of the maximum flow in such window intervals over a time interval [0,T] as T and Lget large, with T substantially bigger than L. We use strong approximations to show that when T≫L≫logT an invariance principle holds, so that the asymptotic behavior depends on the stochastic input process only via its rate and asymptotic variability parameters. In considerable generality, the sliding and jumping windows are asymptotically equivalent. We also develop an approximate relation between the two maximum window sizes. We apply the asympt...
A necessary and sufficient condition is given for the existence of prices that induce coordinatio... more A necessary and sufficient condition is given for the existence of prices that induce coordination in coupled linear dynamic systems. The condition is shown to be equivalent to the servomechanism controllability of an adjoint system.
For the engineering, operation and administration of switching systems, it is desirable to be abl... more For the engineering, operation and administration of switching systems, it is desirable to be able to quickly and accurately estimate the grade of service for different traffic loadings and for hypothetical scenarios and thus to be able to answer what-if questions. This paper presents a probabilistic model that meets this need for a class of overload controls in distributed switching systems. The model is modular and can capture the salient features of a variety of throttle and monitor designs. The model accurately calculates the probability a call is blocked given hypothetical traffic mixes, customer retry probabilities, load imbalances and load variations during the busy hour.
This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Expe... more This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Experience held in January 2016. This seminar was a followup of the seminar on Global Measurement Frameworks held in 2013, which focused on the development of global Internet measurement platforms and associated metrics. The second seminar aimed at discussing the practical experience gained with building these global Internet measurement platforms. It brought together people who are actively involved in the design and maintenance of global Internet measurement platforms and who do research on the data delivered by such platforms. Researchers in this seminar have used data derived from global Internet measurement platforms in order to manage networks or services or as input for regulatory decisions. The entire set of presentations delivered during the seminar is made publicly available at [1].
Proceedings of the ACM Internet Measurement Conference, 2020
This work presents a large-scale, longitudinal measurement study on the adoption of application u... more This work presents a large-scale, longitudinal measurement study on the adoption of application updates, enabling continuous reporting of potentially vulnerable software populations worldwide. Studying the factors impacting software currentness, we investigate and discuss the impact of the platform and its updating strategies on software currentness, device lock-in effects, as well as user behavior. Utilizing HTTP User-Agent strings from end-hosts, we introduce techniques to extract application and operating system information from myriad structures, infer version release dates of applications, and measure population adoption, at a global scale. To deal with loosely structured User-Agent data, we develop a semi-supervised method that can reliably extract application and version information for some 87% of requests served by a major CDN every day. Using this methodology, we track release and adoption dynamics of some 35,000 applications. Analyzing over three years of CDN logs, we sho...
This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Expe... more This article summarises a 2.5 day long Dagstuhl seminar on Global Measurements: Practice and Experience held in January 2016. This seminar was a followup of the seminar on Global Measurement Frameworks held in 2013, which focused on the development of global Internet measurement platforms and associated metrics. The second seminar aimed at discussing the practical experience gained with building these global Internet measurement platforms. It brought together people who are actively involved in the design and maintenance of global Internet measurement platforms and who do research on the data delivered by such platforms. Researchers in this seminar have used data derived from global Internet measurement platforms in order to manage networks or services or as input for regulatory decisions. The entire set of presentations delivered during the seminar is made publicly available at [1].
Probability in the Engineering and Informational Sciences, 1995
Motivated by extreme-value engineering in service systems, we develop and evaluate simple approxi... more Motivated by extreme-value engineering in service systems, we develop and evaluate simple approximations for the distributions of maximum values of queueing processes over large time intervals. We provide approximations for several different processes, such as the waiting times of successive customers, the remaining workload at an arbitrary time, and the queue length at an arbitrary time, in a variety of models. All our approximations are based on extreme-value limit theorems. Our first approach is to approximate the queueing process by one-dimensional reflected Brownian motion (RBM). We then apply the extremevalue limit for RBM, which we derive here. Our second approach starts from exponential asymptotics for the tail of the steady-state distribution. We obtain an approximation by relating the given process to an associated sequence of i.i.d. random variables with the same asymptotic exponential tail. We use estimates of the asymptotic variance of the queueing process to determine ...
Journal of Applied Mathematics and Stochastic Analysis, 1994
An open-loop window flow-control scheme regulates the flow into a system by allowing at most a sp... more An open-loop window flow-control scheme regulates the flow into a system by allowing at most a specified window size W of flow in any interval of length L. The sliding window considers all subintervals of length L, while the jumping window considers consecutive disjoint intervals of length L. To better understand how these window control schemes perform for stationary sources, we describe for a large class of stochastic input processes the asymptotic behavior of the maximum flow in such window intervals over a time interval [0,T] as T and Lget large, with T substantially bigger than L. We use strong approximations to show that when T≫L≫logT an invariance principle holds, so that the asymptotic behavior depends on the stochastic input process only via its rate and asymptotic variability parameters. In considerable generality, the sliding and jumping windows are asymptotically equivalent. We also develop an approximate relation between the two maximum window sizes. We apply the asympt...
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