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1. A Hop Away from Everywhere: A View of the Intercontinental Long-haul Infrastructure

   Carisimo, Esteban; Wang, Caleb J; Weaver, Maria; Bustamante, Fabian E; Barford, Paul (July 2024, ACM SIGMETRICS Performance Evaluation Review)

   We present a longitudinal study of intercontinental long-haul links (LHL) - links with latencies significantly higher than that of all other links in a traceroute path. Our study is motivated by the recognition of these LHLs as a network-layer manifestation of transoceanic undersea cables. We present a methodology and associated processing system for identifying long-haul links in traceroute measurements, and report on our findings from. We apply this system to a large corpus of traceroute data and report on multiple aspects of long haul connectivity including country-level prevalence, routers as international gateways, preferred long-haul destinations, and the evolution of these characteristics over a 7 year period. 

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2. A Hop Away from Everywhere: A View of the Intercontinental Long-haul Infrastructure

   https://doi.org/10.1145/3626778  

   Carisimo, Esteban; Wang, Caleb J; Weaver, Mia; Bustamante, Fabián E; Barford, Paul (December 2023, Proceedings of the ACM on Measurement and Analysis of Computing Systems)

   We present a longitudinal study of intercontinental long-haul links (LHLs) - links with latencies significantly higher than that of all other links in a traceroute path. Our study is motivated by the recognition of these LHLs as a network-layer manifestation of critical transoceanic undersea cables. We present a methodology and associated processing system for identifying long-haul links in traceroute measurements. We apply this system to a large corpus of traceroute data and report on multiple aspects of long haul connectivity including country-level prevalence, routers as international gateways, preferred long-haul destinations, and the evolution of these characteristics over a 7 year period. We identify 85,620 layer-3 links (out of 2.7M links in a large traceroute dataset) that satisfy our definition for intercontinental long haul with many of them terminating in a relatively small number of nodes. An analysis of connected components shows a clearly dominant component with a relative size that remains stable despite a significant growth of the long-haul infrastructure. 

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3. A Manifold View of Connectivity in the Private Backbone Networks of Hyperscalers

   https://doi.org/10.1145/3604620  

   Salamatian, Loqman; Anderson, Scott; Mathews, Joshua; Barford, Paul; Willinger, Walter; Crovella, Mark (August 2023, Communications of the ACM)

   As hyperscalers such as Google, Microsoft, and Amazon play an increasingly important role in today's Internet, they are also capable of manipulating probe packets that traverse their privately owned and operated backbones. As a result, standard traceroute-based measurement techniques are no longer a reliable means for assessing network connectivity in these global-scale cloud provider infrastructures. In response to these developments, we present a new empirical approach for elucidating connectivity in these private backbone networks. Our approach relies on using only lightweight (i.e., simple, easily interpretable, and readily available) measurements, but requires applying heavyweight mathematical techniques for analyzing these measurements. In particular, we describe a new method that uses network latency measurements and relies on concepts from Riemannian geometry (i.e., Ricci curvature) to assess the characteristics of the connectivity fabric of a given network infrastructure. We complement this method with a visualization tool that generates a novel manifold view of a network's delay space. We demonstrate our approach by utilizing latency measurements from available vantage points and virtual machines running in datacenters of three large cloud providers to study different aspects of connectivity in their private backbones and show how our generated manifold views enable us to expose and visualize critical aspects of this connectivity. 

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4. Electrical driving of X-band mechanical waves in a silicon photonic circuit

   https://doi.org/10.1063/1.5042428  

   Van_Laer, Raphaël; Patel, Rishi_N; McKenna, Timothy_P; Witmer, Jeremy_D; Safavi-Naeini, Amir_H (August 2018, APL Photonics)

   Reducing energy dissipation is a central goal of classical and quantum technologies. Optics achieved great success in bringing down power consumption of long-distance communication links. With the rise of mobile, quantum, and cloud technologies, it is essential to extend this success to shorter links. Electro-optic modulators are a crucial contributor of dissipation in such links. Numerous variations on important mechanisms such as free-carrier modulation and the Pockels effect are currently pursued, but there are few investigations of mechanical motion as an electro-optic mechanism in silicon. In this work, we demonstrate electrical driving and optical read-out of a 7.2 GHz mechanical mode of a silicon photonic waveguide. The electrical driving is capacitive and can be implemented in any material system. The measurements show that the mechanically mediated optical phase modulation is two orders of magnitude more efficient than the background phase modulation in our system. Our demonstration is an important step toward efficient opto-electro-mechanical devices in a scalable photonic platform. 

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5. The effects of human exposure on Galápagos sea lion behavior

   https://doi.org/10.2981/wlb.00778  

   Walsh, Justin_T; Kovaka, Karen; Vaca, Ernesto; Weisberg, Deena_Skolnick; Weisberg, Michael (December 2020, Wildlife Biology)

   The endangered Galápagos sea lion lives among a rapidly growing human population, and conflicts between humans and sea lions are increasing. Protection of this fragile species requires a better understanding of how anthropogenic activity affects its health and survival. In this study, we engaged a group of local students in a community science project to conduct long‐term observations of the effects of human disturbance on sea lion behavior. We compared three types of behavior – reaction to human approach, vocalizations and group size – across four different haul‐out sites which varied in their levels of human disturbance. We found that sea lions respond less aggressively to humans on beaches that are more disturbed. This may be because sea lions acclimate to human disturbance or because sea lions with a low tolerance for humans avoid disturbed sites. We also found that aggressive vocalizations between sea lions increase as sea lion group size increases, though group size was not linked to human disturbance. We did not quantify stress levels, but aggressive behavior often indicates elevated stress levels, which are energetically costly and can impair immune function. Our results suggest that conservation efforts should focus on limiting human–sea lion interactions and increasing the number and quality of available haul‐out sites. 

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