Estimating Dynamic Traffic Matrices by using Viable Routing Changes

Abstract: In this paper we propose a new approach for dealing with the ill-posed nature of traffic matrix estimation. We present three solution enhancers: an algorithm for deliberately changing link weights to obtain additional information that can make the underlying linear system full rank; a cyclo-stationary model to capture both long-term and short-term traffic variability, and a method for estimating the variance of origin-destination (OD) flows. We show how these three elements can be combined into a comprehensive traffic matrix estimation procedure that dramatically reduces the errors compared to existing methods. We demonstrate that our variance estimates can be used to identify the elephant OD flows, and we thus propose a variant of our algorithm that addresses the problem of estimating only the heavy flows in a traffic matrix. One of our key findings is that by focusing only on heavy flows, we can simplify the measurement and estimation procedure so as to render it more practical. Although there is a tradeoff between practicality and accuracy, we find that increasing the rank is so helpful that we can nevertheless keep the average errors consistently below the 10% carrier target error rate. We validate the effectiveness of our methodology and the intuition behind it using commercial traffic matrix data from Sprint's Tier-1 backbon

How Will American Households Respond to the New Tax Reform?

A historical tax cut was one of the promises President Donald Trump made during his presidential campaign. On December 22nd, 2017 that proposal was enacted into a law that aims to revitalize the United States’ economy. To achieve this goal, there is one action that the government expects American households will respond to: savings. According to the House Speaker Paul Ryan, the H.R. 1, Tax Cuts and Jobs Act “provides particular relief to low income and middle class families to make sure they keep more of their hard-earned money” (n.d). From this Government’s perspective, saving should prevail over consumption for an economic growth in the short term. The dilemma comes when how the target audience, in this case American households will respond to this stimulus. Thus, this research addresses two questions: 1. How American households have responded regarding consumption and saving due to past tax cuts? 2. What would be the households’ response to consumption and saving with the new H.R. 1, Tax Cuts and Jobs Act enacted by President Donald Trump’s administration

Teaching archive skills: a pedagogical journey with impact

This article considers the pedagogical practice of the Special Collections staff team at the University of Sussex and the impact of the group visit experience on student learning. It addresses our current group visit teaching offer to students at the University of Sussex and our move to a more student-led active learning approach. It considers the use of the ‘pedagogical toolkit’ including technology within the classroom, and the creation of a document identification form to encourage critical thinking. Our aim for any group visit is to provide a positive first experience and get students enthused about using archives. In 2017 we undertook our own impact study, detailed within the article, to follow the student journey with the intention of finding out if students returned to use archives for their studies as a result of their group visit. Moving forward, this article considers our future activities in response to the impact study and institutional initiatives

Peer-to-Peer Communication Across Network Address Translators

Network Address Translation (NAT) causes well-known difficulties for peer-to-peer (P2P) communication, since the peers involved may not be reachable at any globally valid IP address. Several NAT traversal techniques are known, but their documentation is slim, and data about their robustness or relative merits is slimmer. This paper documents and analyzes one of the simplest but most robust and practical NAT traversal techniques, commonly known as "hole punching." Hole punching is moderately well-understood for UDP communication, but we show how it can be reliably used to set up peer-to-peer TCP streams as well. After gathering data on the reliability of this technique on a wide variety of deployed NATs, we find that about 82% of the NATs tested support hole punching for UDP, and about 64% support hole punching for TCP streams. As NAT vendors become increasingly conscious of the needs of important P2P applications such as Voice over IP and online gaming protocols, support for hole punching is likely to increase in the future.Comment: 8 figures, 1 tabl

Improving early design stage timing modeling in multicore based real-time systems

This paper presents a modelling approach for the timing behavior of real-time embedded systems (RTES) in early design phases. The model focuses on multicore processors - accepted as the next computing platform for RTES - and in particular it predicts the contention tasks suffer in the access to multicore on-chip shared resources. The model presents the key properties of not requiring the application's source code or binary and having high-accuracy and low overhead. The former is of paramount importance in those common scenarios in which several software suppliers work in parallel implementing different applications for a system integrator, subject to different intellectual property (IP) constraints. Our model helps reducing the risk of exceeding the assigned budgets for each application in late design stages and its associated costs.This work has received funding from the European Space Agency under Project Reference AO=17722=13=NL=LvH, and has also been supported by the Spanish Ministry of Science and Innovation grant TIN2015-65316-P. Jaume Abella has been partially supported by the MINECO under Ramon y Cajal postdoctoral fellowship number RYC-2013-14717.Peer ReviewedPostprint (author's final draft