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  1. The main premise of this work is that since large cloud providers can and do manipulate probe packets that traverse their privately owned and operated backbones, standard traceroute-based measurement techniques are no longer a reliable means for assessing network connectivity in large cloud provider infrastructures. In response to these developments, we present a new empirical approach for elucidating private connectivity in today's Internet. Our approach relies on using only "light-weight" ( i.e., simple, easily-interpretable, and readily available) measurements, but requires applying a "heavy-weight" or advanced mathematical analysis. In particular, we describe a new method for assessing the characteristics of network path connectivity that is based on concepts from Riemannian geometry ( i.e., Ricci curvature) and also relies on an array of carefully crafted visualizations ( e.g., a novel manifold view of a network's delay space). We demonstrate our method by utilizing latency measurements from RIPE Atlas anchors and virtual machines running in data centers of three large cloud providers to (i) study different aspects of connectivity in their private backbones and (ii) show how our manifold-based view enables us to expose and visualize critical aspects of this connectivity over different geographic scales. 
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  4. Optical fiber deployments in metropolitan areas are critical for information distribution to businesses and large segments of the population. In this paper, we describe a char- acterization study of metropolitan area fiber networks in the US. The goal of our work is to elucidate the key aspects of these infrastructures and to assess how they can be enhanced to support growth in cloud-mobile via expanded connectivity to data centers. We collect maps of 204 metro fiber networks and transcribe these into a geographic information system for analysis and visualization. We report on characteristics including raw miles, geography, proximity to users, correspondence to other infrastructure and PoP/data center proximity. These characteris- tics indicate highly diverse deployments in different metro areas and suggest different strategies for future deployments. Next, we conduct a resource allocation analysis to assess how fiber infrastructure can be deployed in metro areas to reduce the physical distance to data centers over a range of cost scenarios. Our results show that a small number of new connections to data centers can significantly reduce physical distances to users. 
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  5. In this paper, we report on our investigation of how current local time is reported accurately by devices connected to the internet. We describe the basic mechanisms for time management and focus on a critical but unstudied aspect of managing time on connected devices: the time zone database (TZDB). Our longitudinal analysis of the TZDB highlights how internet time has been managed by a loose confederation of contributors over the past 25 years. We drill down on details of the update process, update types and frequency, and anomalies related to TZDB updates. We find that 76% of TZDB updates include changes to the Daylight Saving Time (DST) rules, indicating that DST has a significant influence on internet-based time keeping. We also find that about 20% of updates were published within 15 days or less from the date of effect, indicating the potential for instability in the system. We also consider the security aspects of time management and identify potential vulnerabilities. We conclude with a set of proposals for enhancing TZDB management and reducing vulnerabilities in the system. 
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  6. Physical infrastructures that facilitate e.g., delivery of power, water and communication capabilities are of intrinsic importance in our daily lives. Accurate maps of physical infrastructures are important for permitting, maintenance, repair and growth but can be considered a commercial and/or security risk. In this paper, we describe a method for obfuscating physical infrastructure maps that removes sensitive details while preserving key features that are important in commercial and research applications. We employ a three-tiered approach: tier 1 does simple location fuzzing, tier 2 maintains connectivity details but randomizes node/link locations, while at tier 3 only distributional properties of a network are preserved. We implement our tiered approach in a tool called Bokeh which operates on GIS shapefiles that include detailed location information of infrastructure and produces obfuscated maps. We describe a case study that applies Bokeh to a number of Internet Service Provider maps. The case study highlights how each tier removes increasing amounts of detail from maps. We discuss how Bokeh can be generally applied to other physical infrastructures or in local services that are increasingly used for e-marketing. 
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  7. In this paper, we describe an architecture for clock synchronization in IoT devices that is designed to be scalable, flexibly accommodate diverse hardware, and maintain tight synchronization over a range of operating conditions. We begin by examining clock drift on two standard IoT prototyping platforms. We observe clock drift on the order of seconds over relatively short time periods, as well as poor clock rate stability, each of which make standard synchronization protocols ineffective. To address this problem, we develop a synchronization system, which includes a lightweight client, a new packet exchange protocol called SPoT and a scalable reference server. We evaluate the efficacy of our system over a range of configurations, operating conditions and target platforms. We find that SPoT performs synchronization 22x and 17x more accurately than MQTT and SNTP, respectively, at high noise levels, and maintains a clock accuracy of within ∼15ms at various noise levels. Finally, we report on the scalability of our server implementation through microbenchmark and wide area experiments, which show that our system can scale to support large numbers of clients efficiently. 
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  8. One-way delay (OWD) between end hosts has important implications for Internet applications, protocols, and measurement-based analyses. We describe a new approach for identifying OWDs via passive measurement of Network Time Protocol (NTP) traffic. NTP traffic offers the opportunity to measure OWDs accurately and continuously from hosts throughout the Internet. Based on detailed examination of NTP implementations and in-situ behavior, we develop an analysis tool that we call TimeWeaver, which enables assessment of precision and accuracy of OWD measurements from NTP. We apply TimeWeaver to a ∼1TB corpus of NTP traffic collected from 19 servers located in the US and report on the characteristics of hosts and their associated OWDs, which we classify in a precision/accuracy hierarchy. To demonstrate the utility of these measurements, we apply iterative hard-threshold singular value decomposition to estimate the missing OWDs between arbitrary hosts from the highest tier in the hierarchy. We show that this approach results in highly accurate estimates of missing OWDs, with average error rates on the order of less than 2%. 
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