I am a researcher at Internet Initiative Japan (IIJ) Research Laboratory. Before that, I was a postdoc at CAIDA, UC San Diego
and at the CMAND lab
at NPS in Monterey, California.
I completed my Ph.D. in computer science at the Internet Network Architectures (INET) group, Technische Universität
Berlin.
My research investigates the security, scalability, and resilience of distributed systems, particularly Internet routing systems, using data-driven modeling and measurement infrastructure.
A central premise of my work is that a meaningful understanding of BGP requires understanding BGP communities.
Communities encode much of the routing policy, operational intent, and location information that govern how
routes are propagated and selected in practice, yet they remain largely opaque: the vast majority of communities
observed in the wild lack public documentation.
I develop models that extract structure and meaning from undocumented BGP communities, enabling inference of routing intent and the interaction between logical connectivity and physical geography. By making these signals interpretable, my research aims to explain how policy and deployment decisions shape the robustness of Internet connectivity.
Beyond routing policy, I also investigate the deployment and effectiveness of key Internet security mechanisms, including RPKI and DDoS protection services, with the goal of understanding their real-world adoption, operational trade-offs, and impact on Internet resilience.
To support this work, I design and operate measurement infrastructure that broadens visibility into Internet routing and enables large-scale, longitudinal, and reproducible analysis of BGP behavior. This includes community-facing services such as BGP2GO, which lowers the barrier to routing analysis by allowing users to efficiently locate relevant BGP update data without downloading large volumes of raw measurements.
This research agenda develops along two main directions: interpreting routing policy signals encoded in BGP communities, and expanding the measurement infrastructure used to study Internet routing behavior.
Much of the operational logic of Internet routing is encoded in BGP communities,
which network operators use to signal routing policy, operational intent, and geographic location.
In the IMC paper “Coarse-grained Inference of BGP Community Intent”
(Best Paper Runner-up), I demonstrated how coarse-grained routing policies encoded in communities
can be systematically interpreted using large-scale BGP measurements and operator-documented
community semantics, building a cornerstone for subsequent finer-grained inference methods.
Building on this foundation, my more recent work investigates how BGP location communities can be used to
infer where networks interconnect geographically. This includes the CoNEXT paper “Towards
Understanding City-Level Routing Using BGP Location Communities” and my ongoing APNIC-
funded project “Mapping Internet Peering Locations for Resilience and Policy in the Asia-Pacific.”
Together, this line of work aims to reveal the geographic and policy-shaped structure of Internet
connectivity using signals embedded in public routing data.
A second research direction focuses on improving the infrastructure used to collect BGP data for
Internet measurement. In the SIGCOMM Best Paper “The Next Generation of BGP Data Collection
Platforms,” I contributed to the design of a novel sampling strategy for selectively collecting BGP
updates from an order of magnitude larger set of BGP peers than traditional systems. This significantly
improves visibility into global routing dynamics and helps mitigate the long-standing hidden-link
problem in BGP measurements.
Another effort in this direction is BGPFiend, a
modular framework for exploring and analyzing BGP data and BGP communities. This work will be
presented as an INFOCOM poster titled “Modernizing BGP Data Access with BGPFiend.” The goal of
this line of work is to modernize the infrastructure used in Internet measurement and enable researchers
to more easily build datasets and analyses of global routing behavior.
XoX: A System for Fast, Accurate, and Intuitive Querying of Large-Scale BGP Datasets Thomas Holterbach, Thomas Alfroy, Abbas Mohsenpour, Thomas Krenc, kc claffy, Cristel Pelsser
To appear in ACM IMC'26
Constructing a High-precision and Semantically Rich BGP Community Dictionary via LLMs Yizhe Zhang, Hongying Dong, Anxiao He, Guanlong Wu, Thomas Krenc, Hyojoon Kim, Yixin Sun
To appear in ACM CoNEXT'26
Modernizing BGP Data Access with BGPFiend Thomas Krenc, Justin Loye, Dimitrios Giakatos, Hans Kuhn, Owen Conway, Ties de Kock, kc claffy
@inproceedings{krenc2026modernizing,
title={Modernizing BGP Data Access with BGPFiend},
author={Krenc, Thomas and Loye, Justin and Giakatos, Dimitrios and Kuhn, Hans and Conway, Owen A and de Kock, Ties and Claffy, Kimberly},
booktitle={IEEE INFOCOM 2026-IEEE Conference on Computer Communications},
pages={3689--3690},
year={2026},
organization={IEEE}
}
Towards Understanding City-Level Routing using BGP Location Communities Thomas Krenc, Shivani Hariprasad, Matthew Luckie, Benoit Donnet, kc claffy
@article{krenc2025towards,
title={Towards Understanding City-Level Routing using BGP Location Communities},
author={Krenc, Thomas and Hariprasad, Shivani and Luckie, Matthew and Donnet, Benoit and Claffy, kc},
journal={Proceedings of the ACM on Networking},
volume={3},
number={CoNEXT4},
pages={1--13},
year={2025},
publisher={ACM New York, NY, USA}
}
Noisy Neighbours: Keep the Neighbourhood Quiet Ebrima Jaw, Thomas Krenc, Moritz Müller, kc claffy, Lambert Nieuwenhuis, Cristian Hesselman
@inproceedings{jaw2025noisy,
title={Noisy neighbours: Keep the neighbourhood quiet},
author={Jaw, Ebrima and Krenc, Thomas and M{\"u}ller, Moritz and Claffy, Kc and Nieuwenhuis, Lambert and Hesselman, Cristian},
booktitle={2025 21st International Conference on Network and Service Management (CNSM)},
pages={1--9},
year={2025},
organization={IEEE}
}
The Next Generation of BGP Data Collection Platforms Thomas Alfroy, Thomas Holterbach, Thomas Krenc, kc claffy, Cristel Pelsser
@inproceedings{alfroy2024next,
title={The Next Generation of BGP Data Collection Platforms},
author={Alfroy, Thomas and Holterbach, Thomas and Krenc, Thomas and Claffy, KC and Pelsser, Cristel},
booktitle={Proceedings of the ACM SIGCOMM 2024 Conference},
pages={794--812},
year={2024}
}
Measuring Internet Routing from the Most Valuable Points Thomas Alfroy, Thomas Holterbach, Thomas Krenc, kc claffy, Cristel Pelsser
@misc{alfroy2024measuringinternetroutingvaluable,
title={Measuring Internet Routing from the Most Valuable Points},
author={Thomas Alfroy and Thomas Holterbach and Thomas Krenc and KC Claffy and Cristel Pelsser},
year={2024},
eprint={2405.13172},
archivePrefix={arXiv},
primaryClass={cs.NI},
url={https://arxiv.org/abs/2405.13172},
}
Internet Science Moonshot: Expanding BGP Data Horizons Thomas Alfroy, Thomas Holterbach, Thomas Krenc, kc claffy, Cristel Pelsser
@inproceedings{alfroy2023internet,
title={Internet science moonshot: Expanding BGP data horizons},
author={Alfroy, Thomas and Holterbach, Thomas and Krenc, Thomas and Claffy, KC and Pelsser, Cristel},
booktitle={Proceedings of the 22nd ACM Workshop on Hot Topics in Networks},
pages={102--108},
year={2023}
}
Coarse-grained Inference of BGP Community Intent Thomas Krenc, Matthew Luckie, Alexander Marder, kc claffy
@inproceedings{krenc2023coarse,
title={Coarse-grained Inference of BGP Community Intent},
author={Krenc, Thomas and Luckie, Matthew and Marder, Alexander and claffy, kc},
booktitle={Proceedings of the 2023 ACM on Internet Measurement Conference},
pages={66--72},
year={2023}
}
IRR Hygiene in the RPKI Era Ben Du, Gautam Akiwate, Thomas Krenc, Cecilia Testart, Alexander Marder, Bradley Huffaker, Alex C. Snoeren, and kc claffy In PAM'22
@inproceedings{du2022irr,
title={IRR Hygiene in the RPKI Era},
author={Du, Ben and Akiwate, Gautam and Krenc, Thomas and Testart, Cecilia and Marder, Alexander and Huffaker, Bradley and Snoeren, Alex C and Claffy, Kimberly C},
booktitle={International Conference on Passive and Active Network Measurement},
pages={321--337},
year={2022},
organization={Springer}
}
AS-Level BGP Community Usage Classification Thomas Krenc, Robert Beverly and Georgios Smaragdakis
@inproceedings{krenc2021level,
title={AS-level BGP community usage classification},
author={Krenc, Thomas and Beverly, Robert and Smaragdakis, Georgios},
booktitle={Proceedings of the 21st ACM Internet Measurement Conference},
pages={577--592},
year={2021}
}
Keep your Communities Clean: Exploring the Routing Message Impact of BGP Communities Thomas Krenc, Robert Beverly and Georgios Smaragdakis In ACM CoNEXT'20
@inproceedings{krenc2020keep,
title={Keep your communities clean: exploring the routing message impact of BGP communities},
author={Krenc, Thomas and Beverly, Robert and Smaragdakis, Georgios},
booktitle={Proceedings of the 16th International Conference on emerging Networking EXperiments and Technologies},
pages={443--450},
year={2020}
}
BGP Prefix Delegations: A Deep Dive Thomas Krenc and Anja Feldmann In ACM IMC'16
@inproceedings{krenc2016bgp,
title={BGP prefix delegations: a deep dive},
author={Krenc, Thomas and Feldmann, Anja},
booktitle={Proceedings of the 2016 Internet Measurement Conference},
pages={469--475},
year={2016}
}
An Internet Census Taken by an Illegal Botnet: A Qualitative Assessment of Published Measurements Thomas Krenc, Oliver Hohlfeld and Anja Feldmann In ACM SIGCOMM CCR (2014)
@misc{krenc2014internet,
title={An internet census taken by an illegal botnet: a qualitative assessment of published measurements},
author={Krenc, Thomas and Hohlfeld, Oliver and Feldmann, Anja},
journal={ACM SIGCOMM Computer Communication Review},
volume={44},
number={3},
pages={103--111},
year={2014},
publisher={ACM New York, NY, USA}
}
On the Benefits of Using a Large IXP As an Internet Vantage Point Nikolaos Chatzis, Georgios Smaragdakis, Jan Böttger, Thomas Krenc and Anja Feldmann In ACM IMC'13
@inproceedings{chatzis2013benefits,
title={On the benefits of using a large IXP as an Internet vantage point},
author={Chatzis, Nikolaos and Smaragdakis, Georgios and B{\"o}ttger, Jan and Krenc, Thomas and Feldmann, Anja},
booktitle={Proceedings of the 2013 conference on Internet measurement conference},
pages={333--346},
year={2013}
}
Service
Internet Measurement Conference (IMC): 2024, 2025, 2026
Conference on emerging Networking EXperiments and Technologies (CoNEXT): 2026
Passive and Active Measurement Conference (PAM): 2022, 2023, 2024, 2025, 2026
Network Traffic Measurement and Analysis Conference (TMA): 2026