VLDB 2026 Research / reviewers in the wild / expert
Zachary S. Bischof
dblp:14/5053
· DBLP profile ↗
25ranked-venue papers
6as first author
10since 2021 · last 2025
0000-0001-6419-6303ORCID · verified
Domains — the database's venue-derived domains; a paper can count in several
Computer networks · 19 · 5 first-author · 8 since 2021Security and privacy · 4 · 1 first-author · 2 since 2021Applied, interdisciplinary, general and emerging computing · 2Artificial intelligence and machine learning · 1Databases, data management, data science and information retrieval · 1
| Year | Publication | Venue | Position |
|---|---|---|---|
| 2025 | Replication: A Two Decade Review of Policy Atoms - Tracing the Evolution of AS Path Sharing PrefixesabstractAfek et al. characterized the formation and stability of policy atoms, groups of prefixes that share the same Autonomous System (AS) paths as observed by BGP collectors, a concept initially defined by Broido and Claffy in 2001. Policy atoms provide a valuable perspective on the inter-domain routing policies in the Internet. With the rapid growth and increasing complexity of the Internet since these studies, we believe it is important to reassess the implications and applicability of policy atoms. In this paper, we revisit the policy atom concept after two decades and replicate the study performed by Afek et al. to assess the current state of AS path sharing and shed light on the evolution of policy atoms. We demonstrate that the Internet still operates on the level of policy atoms rather than individual ASes, as prefixes within the same atom tend to experience changes in AS path simultaneously. We apply the concept of policy atoms in IPv6 and find that this observation also holds true for IPv6 prefixes. We also relate trends in the characteristics of policy atoms with the development of inter-domain routing policies. We highlight new insights generated by the perspective of policy atoms and their potential for further applications. Our code is publicly available to support reproducibility and to encourage future research on this topic. Weili Wu 0004, Zachary S. Bischof, Cecilia Testart, Alberto Dainotti |
IMC | 2 |
| 2025 | Assessing LEO Satellite Networks for National Emergency FailoverabstractIn this paper, we study the viability of LEO networks as a failover network. We contextualize our analysis by framing the capacity of satellite networks relative to lost capacity due to submarine cable failure. Specifically, we focus on scenarios where LEO networks act as failovers for submarine cables, providing a concrete target capacity to be fulfilled by the satellite network. We introduce a new model and simulator that help us estimate the failover capacity. We identify key factors determining the actual capacity available on the satellite network: the total area of the country, the terminal distribution policy used by the government, the spectrum allocation and traffic engineering policies used by the LEO network operator. Based on our findings, we make policy recommendations to governments that can result in an increase of up to 1.8× in the failover capacity without requiring additional infrastructure. However, we find after implementing all our recommendations, with 200k terminals deployed and no competing traffic in the network, a satellite network can only satisfy 0.9-14.7% of the capacity lost due to submarine cable failure in four out of six case studies. Vaibhav Bhosale, Sameer S. Kapoor, Robin Kim, Miguel T. Schlicht, Muskaan Gupta, Ekaterina Tumanova, Zachary S. Bischof, Fabián E. Bustamante, Alberto Dainotti, Ahmed Saeed 0001 |
IMC | 8 |
| 2024 | Poster: Enhancing Internet Disruption Investigation via Path MonitoringabstractLarge-scale Internet disruptions, ranging from complete disconnections to service degradations, are increasingly common, due to factors such as government-ordered shutdowns, infrastructure failures, and sophisticated traffic manipulation techniques. While existing detection platforms are effective at identifying complete disconnections, they fail to detect service degradations, such as those caused by throttling, intentional rerouting, or network attacks, which degrade performance without blocking connectivity. In this poster, we discuss our plan to improve Internet disruption investigation through additional metrics (loss, latency) and measurement techniques (traceroutes) to help identify such events and provide researchers with the network-level information necessary for investigation. Our method not only helps to identify service degradations missed by traditional connectivity checks but also provides data for generating insights into the underlying causes and impacts of Internet disruptions. Weili Wu 0004, Zachary S. Bischof, Cecilia Testart, Alberto Dainotti |
IMC | 2 |
| 2024 | The Wisdom of the Measurement Crowd: Building the Internet Yellow Pages a Knowledge Graph for the InternetabstractThe Internet measurement community has significantly advanced our understanding of the Internet by documenting its various components. Subsequent research often builds on these efforts, using previously published datasets. This process is fundamental for researchers, but a laborious task due to the diverse data formats, terminologies, and areas of expertise involved. Additionally, the time-consuming task of merging datasets is undertaken only if the expected benefits are worthwhile, posing a barrier to simple exploration and innovation. In this paper we present the Internet Yellow Pages (IYP), a knowledge graph for Internet resources. By leveraging the flexibility of graph databases and ontology-based data integration, we compile datasets (currently 46) from diverse and independent sources into a single harmonized database where the meaning of each entity and relationship is unequivocal. Using simple examples, we illustrate how IYP allows us to seamlessly navigate data coming from numerous underlying sources. As a result, IYP significantly reduces time to insight, which we demonstrate by reproducing two past studies and extending them by incorporating additional datasets available in IYP. Finally, we discuss how IYP can foster the sharing of datasets as it provides a universal platform for querying and describing data. This is a seminal effort to bootstrap what we envision as a community-driven project where dataset curation and ontology definitions evolve with the Internet measurement community. Romain Fontugne, Malte Tashiro, Raffaele Sommese, Mattijs Jonker, Zachary S. Bischof, Emile Aben |
IMC | 5 |
| 2024 | Towards Improving Outage Detection with Multiple Probing Protocols
Manasvini Sethuraman, Zachary S. Bischof, Alberto Dainotti |
PAM (1) | 2 |
| 2023 | Improving the Inference of Sibling Autonomous Systems
Zachary S. Bischof, Cecilia Testart, Alberto Dainotti |
PAM | 2 |
| 2023 | Destination Unreachable: Characterizing Internet Outages and ShutdownsabstractIn this paper, we provide the first comprehensive longitudinal analysis of government-ordered Internet shutdowns and spontaneous outages (i.e., disruptions not ordered by the government). We describe the available tools, data sources and methods to identify and analyze Internet shutdowns. We then merge manually curated datasets on known government-ordered shutdowns and large-scale Internet outages, further augmenting them with data on real-world events, macroeconomic and sociopolitical indicators, and network operator statistics. Our analysis confirms previous findings on the economic and political profiles of countries with government-ordered shutdowns. Extending this analysis, we find that countries with national-scale spontaneous outages often have profiles similar to countries with shutdowns, differing from countries that experience neither. However, we find that government-ordered shutdowns are many more times likely to occur on days of mobilization, coinciding with elections, protests, and coups. Our study also characterizes the temporal characteristics of Internet shutdowns and finds that they differ significantly in terms of duration, recurrence interval, and start times when compared to spontaneous outages. Zachary S. Bischof, Kennedy Pitcher, Esteban Carisimo, Amanda Meng, Rafael Bezerra Nunes, Ramakrishna Padmanabhan, Margaret E. Roberts, Alex C. Snoeren, Alberto Dainotti |
SIGCOMM | 1 |
| 2022 | iGDB: connecting the physical and logical layers of the internetabstractMaps of physical and logical Internet connectivity that are informed by and consistent with each other can expand scope and improve accuracy in analysis of performance, robustness and security. In this paper, we describe a methodology for linking physical and logical Internet maps that aims toward a consistent, cross-layer representation. Our approach is constructive and uses geographic location as the key feature for linking physical and logical layers. We begin by building a representation of physical connectivity using online sources to identify locations that house transport hardware (i.e., PoPs, colocation centers, IXPs, etc.), and approximate locations of links between these based on shortest-path rights-of-way. We then utilize standard data sources for generating maps of IP-level and AS-level logical connectivity, and graft these onto physical maps using geographic anchors. We implement our methodology in an open-source framework called the Internet Geographic Database (iGDB), which includes tools for updating measurement data and assuring internal consistency. iGDB is built to be used with ArcGIS, a geographic information system that provides broad capability for spatial analysis and visualization. We describe the details of the iGDB implementation and demonstrate how it can be used in a variety of settings. Scott Anderson, Loqman Salamatian, Zachary S. Bischof, Alberto Dainotti, Paul Barford |
IMC | 3 |
| 2022 | Analysis of IPv4 address space utilization with ANT ISI dataset and censysabstractSince 2003, the ANT Lab at ISI has used active measurements to conduct a census of the IPv4 address space [1]. Each census lasts approximately 2--3 months, scanning the entire IPv4 address space using ICMP ping probes and recording replies. To date, there have been 85 surveys. One of the by-products of these surveys is the address history dataset [5], which contains the ICMP responses from more than 1.4 billion IPv4 addresses over an 18 year period, starting in 2006. Manasvini Sethuraman, Zachary S. Bischof, Alberto Dainotti |
IMC | 2 |
| 2021 | Learning to extract geographic information from internet router hostnamesabstractGeolocating Internet routers is a long-standing and notoriously difficult challenge, and current solutions lack the accuracy and adaptability to yield reliable results. We revisit this problem, designing a solution capable of accurately and comprehensively extracting geographic information that network operators embed into router interface hostnames. We train our system using dictionaries that map geographic codes to known locations, and constrain inferences with delay measurements conducted from a distributed set of vantage points. While most operators use known geographic codes, some devise their own mnemonic codes for locations, which our system also extracts and interprets. Matthew J. Luckie, Bradley Huffaker, Alexander Marder, Zachary S. Bischof, Marianne Fletcher, K. C. Claffy |
CoNEXT | 4 |
| 2020 | Out of Sight, Not Out of Mind: A User-View on the Criticality of the Submarine Cable NetworkabstractNearly all international data is carried by a mesh of submarine cables connecting virtually every region in the world. It is generally assumed that Internet services rely on this submarine cable network (SCN) for backend traffic, but that most users do not directly depend on it, as popular resources are either local or cached nearby. In this paper, we study the criticality of the SCN from the perspective of end users. We present a general methodology for analyzing the reliance on the SCN for a given region, and apply it to the most popular web resources accessed by users in 63 countries from every inhabited continent, collectively capturing ≈80% of the global Internet population. We find that as many as 64.33% of all web resources accessed from a specific country rely on the SCN. Despite the explosive growth of data center and CDN infrastructure around the world, at least 28.22% of the CDN-hosted resources traverse a submarine cable. Shucheng Liu, Zachary S. Bischof, Ishaan Madan, Peter K. Chan, Fabián E. Bustamante |
Internet Measurement Conference | 2 |
| 2019 | AMP up your Mobile Web Experience: Characterizing the Impact of Google's Accelerated Mobile ProjectabstractThe rapid growth in the number of mobile devices, subscriptions and their associated traffic, has served as motivation for several projects focused on improving mobile users' quality of experience (QoE). Few have been as contentious as the Google-initiated Accelerated Mobile Project (AMP), both praised for its seemingly instant mobile web experience and criticized based on concerns about the enforcement of its formats. This paper presents the first characterization of AMP's impact on users' QoE. We do this using a corpus of over 2,100 AMP webpages, and their corresponding non-AMP counterparts, based on trendy-keyword-based searches. We characterized AMP's impact looking at common web QoE metrics, including Page Load Time, Time to First Byte and SpeedIndex (SI). Our results show that AMP significantly improves SI, yielding on average a 60% lower SI than non-AMP pages without accounting for prefetching. Prefetching of AMP pages pushes this advantage even further, with prefetched pages loading over 2,000ms faster than non-prefetched AMP pages. This clear boost may come, however, at a non-negligible cost for users with limited data plans as it incurs an average of over 1.4~MB of additional data downloaded, unbeknownst to users. Byungjin Jun, Fabián E. Bustamante, Sung Yoon Whang, Zachary S. Bischof |
MobiCom | 4 |
| 2018 | Untangling the world-wide mesh of undersea cablesabstractThe growth of global Internet traffic has driven an exponential expansion of the submarine cable network, both in terms of the sheer number of links and its total capacity. Today, a complex mesh of hundreds of cables, stretching over 1 million kilometers, connects nearly every corner of the earth and is instrumental in closing the remaining connectivity gaps. Despite the scale and critical role of the submarine network for both business and society at large, our community has mostly ignored it, treating it as a black box in most Internet studies, from connectivity to inter-domain traffic and reliability. We make the case for a new research agenda focused on characterizing the global submarine network and the critical role it plays as a basic component of any inter-continental end-to-end connection. Zachary S. Bischof, Romain Fontugne, Fabián E. Bustamante |
HotNets | 1 |
| 2017 | The Utility Argument - Making a Case for Broadband SLAs
Zachary S. Bischof, Fabián E. Bustamante, Rade Stanojevic |
PAM | 1 |
| 2015 | In and Out of Cuba: Characterizing Cuba's ConnectivityabstractThe goal of our work is to characterize the current state of Cuba's access to the wider Internet. This work is motivated by recent improvements in connectivity to the island and the growing commercial interest following the ease of restrictions on travel and trade with the US. In this paper, we profile Cuba's networks, their connections to the rest of the world, and the routes of international traffic going to and from the island. Despite the addition of the ALBA-1 submarine cable, we find that round trip times to websites hosted off the island remain very high; pings to popular websites frequently took over 300 ms. We also find a high degree of path asymmetry in traffic to/from Cuba. Specifically, in our analysis we find that traffic going out of Cuba typically travels through the ALBA-1 cable, but, surprisingly, traffic on the reverse path often traverses high-latency satellite links, adding over 200 ms to round trip times. Last, we analyze queries to public DNS servers and SSL certificate requests to characterize the availability of network services in Cuba. Zachary S. Bischof, John P. Rula, Fabián E. Bustamante |
Internet Measurement Conference | 1 |
| 2015 | A Measurement Experimentation Platform at the Internet's EdgeabstractPoor visibility into the network hampers progress in a number of important research areas, from network troubleshooting to Internet topology and performance mapping. This persistent, well-known problem has served as motivation for numerous proposals to build or extend existing Internet measurement platforms by recruiting larger, more diverse vantage points. Capturing the edge of the network, however, remains an elusive goal. We argue that at its root the problem is one of incentives. Today's measurement platforms build on the assumption that the goals of experimenters and those hosting the platform are the same. As much of the Internet growth occurs in residential broadband networks, this assumption no longer holds. We present a measurement experimentation platform that reaches the network edge by explicitly aligning the objectives of the experimenters with those of the users hosting the platform. Dasu-our current prototype-is designed to support both network measurement experimentation and broadband characterization. Dasu has been publicly available since July 2010 and has been installed by over 100 000 users with a heterogeneous set of connections spreading across 2431 autonomous systems (ASs) and 166 countries. We discuss some of the challenges we faced building and using a platform for the Internet's edge, describe its design and implementation, and illustrate the unique perspective its current deployment brings to Internet measurement. Mario A. Sánchez, John S. Otto, Zachary S. Bischof, David R. Choffnes, Fabián E. Bustamante, Balachander Krishnamurthy, Walter Willinger |
IEEE/ACM Trans. Netw. | 3 |
| 2014 | Need, Want, Can Afford: Broadband Markets and the Behavior of UsersabstractWe present the first study of broadband services in their broader context, evaluating the impact of service characteristics (such as capacity, latency and loss), their broadband pricing and user demand. We explore these relationships, beyond correlation, with the application of natural experiments. Most efforts on broadband service characterization have so far focused on performance and availability, yet we lack a clear understanding of how such services are being utilized and how their use is impacted by the particulars of the market. By analyzing over 23-months of data collected from 53,000 end hosts and residential gateways in 160 countries, along with a global survey of retail broadband plans, we empirically study the relationship between broadband service characteristics, pricing and demand. We show a strong correlation between capacity and demand, even though subscribers rarely fully utilize their links, but note a law of diminishing returns with relatively smaller increases in demand at higher capacities. Despite the fourfold increase in global IP traffic, we find that user demand on the network over a three year period remained constant for a given bandwidth capacity. We exploit natural experiments to examine the causality between these factors. The reported findings represent an important step towards understanding how user behavior, and the market features that shape it, affect broadband networks and the Internet at large. Zachary S. Bischof, Fabián E. Bustamante, Rade Stanojevic |
Internet Measurement Conference | 1 |
| 2014 | A time for reliability: the growing importance of being always onabstractWhen a new technology reaches the market, we typically focus on the want or need that it can fulfill. As the technology becomes a commodity and its market matures, reliability often become a key differentiating factor between competing products. We posit that as broadband capacities continue to improve and users migrate to over-the-Internet services, such as on-demand video and voice-over-IP services, we will see this common pattern emerge for broadband services. In this poster, we present the first study of reliability in broadband networks. Using data collected from residential gateways (via FCC/SamKnows), we study the availability and reliability of fixed-line broadband services across the US. Using natural experiments, we look at the impact of increased network downtime on user network demand. We use traditional metrics (e.g. failure rate, MTBF, MTTR) to quantify broadband services, as well as each ISP's configured DNS. Since the impact of a network outage will depend on when it occurred (e.g. time of day), we compare ISP services by the annual average number of bytes lost, based on typical user demand during periods of network downtime. Zachary S. Bischof, Fabián E. Bustamante |
SIGCOMM | 1 |
| 2014 | A cliq of content curatorsabstractA social news site presents user-curated content, ranked by popularity. Popular curators like Reddit, or Facebook have become effective way of crowdsourcing news or sharing for personal opinions. Traditionally, these services require a centralized authority to aggregate data and determine what to display. However, the trust issues that arise from a centralized system are particularly damaging to the "Web democracy" that social news sites are meant to provide. In this poster, we present cliq, a decentralized social news curator. cliq is a P2P based social news curator that provides private and unbiased reporting. All users in cliq share responsibility for tracking and providing popular content. Any user data that cliq needs to store is also managed across the network. We first inform our design of cliq through an analysis of Reddit. We design a way to provide content curation without a persistent moderator, or usernames. Angela H. Jiang, Zachary S. Bischof, Fabián E. Bustamante |
SIGCOMM | 2 |
| 2013 | Dasu: Pushing Experiments to the Internet's Edge
Mario A. Sánchez, John S. Otto, Zachary S. Bischof, David R. Choffnes, Fabián E. Bustamante, Balachander Krishnamurthy, Walter Willinger |
NSDI | 3 |
| 2013 | Trying Broadband Characterization at Home
Mario A. Sánchez, John S. Otto, Zachary S. Bischof, Fabián E. Bustamante |
PAM | 3 |
| 2011 | Dasu - ISP characterization from the edge: a BitTorrent implementationabstractEvaluating and characterizing access ISPs is critical to consumers shopping for alternative services and governments surveying the availability of broadband services to their citizens. We present Dasu, a service for crowdsourcing ISP characterization to the edge of the network. Dasu is implemented as an extension to a popular BitTorrent client and has been available since July 2010. While the prototype uses BitTorrent as its host application, its design is agnostic to the particular host application. The demo showcases our current implementation using both a prerecorded execution trace and a live run. Mario A. Sánchez, John S. Otto, Zachary S. Bischof, Fabián E. Bustamante |
SIGCOMM | 3 |
| 2011 | Controlled Multi-Path Routing in Sensor Networks Using Bezier CurvesabstractWe address the problem of extending the lifetime of wireless sensor networks using multi-path routing based on a family of flexible routes with soft quality of service guarantees in terms of the packets’ delivery latency. We introduce a methodology based on Bezier curves as guiding trajectories in the routing process and we address the balancing of the workload among neighboring nodes. An added benefit, due to the flexibility of the Bezier curves, is that the shapes of the (alternate) routes can be constructed in a manner that prolongs the lifetime of the nodes in the vicinity of a given source/sink. We describe a forwarding algorithm, where the relay nodes can determine locally the Bezier curve they belong to and which requires only the transmission of the so-called control points that determine the shape of one (boundary) curve. We also show how our forwarding algorithm can be adapted to incorporate the sleep-schedule of the individual nodes, thereby further prolonging the networks’ lifetime. Our simulations demonstrate that the Bezier-based routing algorithms can yield significant improvements in the networks’ overall lifetime. Oliviu Ghica, Goce Trajcevski, Peter Scheuermann, Nikolay Valtchanov, Zachary S. Bischof |
Comput. J. | 5 |
| 2009 | Range queries for mobile objects in wireless sensor networksabstractThis work addresses the problem of processing spatio-temporal range queries when the mobile entities are tracked in Wireless Sensor Network (WSN). We demonstrate that in many realistic settings, depending on the parameters of a given range query, the tracking of a particular moving object may not be needed past certain thresholds in space and/or time. We also propose and analyze distributed data-reduction techniques for the purpose of reducing the energy consumption due to communication. Goce Trajcevski, Zachary S. Bischof, Peter Scheuermann |
GIS | 2 |
| 2008 | SIDnet-SWANS: a simulator and integrated development platform for sensor networks applicationsabstractThis work presents the SIDnet, a simulation-based environment for applications development in wireless sensor networks settings. It enables run-time interactions with the network for the purpose of observing the behavior of algorithms protocols in the presence of various conditions such as phenomena fluctuations, or a sudden loss of service both at an individual node, as well as a collection of nodes. Oliviu Ghica, Goce Trajcevski, Peter Scheuermann, Zachary S. Bischof, Nikolay Valtchanov |
SenSys | 4 |