Thomas Krenc
IIJ Research Laboratory
Iidabashi Grand Bloom
2-10-2 Fujimi, Chiyoda-ku
Tokyo 102-0071
Japan
tkrenc@iij.ad.jp

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.

Parts of my research are supported by the APNIC Research Fellowship.

Publications

Towards Understanding City-Level Routing using BGP Location Communities
Thomas Krenc, Shivani Hariprasad, Matthew Luckie, Benoit Donnet, kc claffy
In ACM CoNEXT'25
[pdf] [website] 
@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
In IFIP CNSM'25
[pdf]

The Next Generation of BGP Data Collection Platforms
Thomas Alfroy, Thomas Holterbach, Thomas Krenc, kc claffy, Cristel Pelsser
In ACM SIGCOMM'24, Best paper award!
[pdf] [website] 
@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} }
Internet Science Moonshot: Expanding BGP Data Horizons
Thomas Alfroy, Thomas Holterbach, Thomas Krenc, kc claffy, Cristel Pelsser
In ACM HotNets'23
[pdf] [website] 
@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
In ACM IMC'23, Best Paper Runners-up!
[pdf] [website] [honorable mention] 
@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
[pdf] 
@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
In ACM IMC'21
[pdf] [website] [article] 
@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
[pdf] [website] 
@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
[pdf] 
@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)
[link] 
@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
[link] 
@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
Passive and Active Measurement Conference (PAM): 2022, 2023, 2024, 2025, 2026
Network Traffic Measurement and Analysis Conference (TMA): 2026


Teaching
INGI Seminar, April 2024, UC Louvain
(guest lecture: "Location Inference of BGP Communities")
INFO8011 (Network Infrastructures), Fall 2023, University of Liège
(guest lecture: "Internet Exchange Points")
Distributed Systems, July 2023, University of Kassel
(guest lecture: "BGP Community Intents")
CSE291-e: Internet Data Science for Cybersecurity, Winter 2023, UCSD
(guest lecture: "BGP Communities")
CSE291: Internet Infrastructure, Fall 2021, UCSD
(guest lecture: "Why IXPs matter")
CS4538: Mobile Device and Wireless Security, Spring 2021, NPS
Network Protocols and Architectures, Fall 2012 - 2018, TU Berlin
(teaching assistant + lecturing)
Internet Routing Seminar, 2013 - 2018, TU Berlin
Internet Measurement Seminar, Spring 2014 - 2015, 2018, TU Berlin
RouterLab, Spring 2014, 2018, 2019, TU Berlin


Bachelor / Master Thesis Supervision
BGP Smalltalk: A Systematic Analysis of BGP Attribute Changes
Kamil Balitzki, TU Berlin, 2022
Sources of Change in Internet Protocol Geolocation Databases
Bryan Kauffman, NPS, 2021
Autonomous System Choke Points in Country-Level Network Topology
Eric Regnier, NPS, 2021
Chasing the Unknown: A Predictive Model to Demystify BGP Community Semantics
Joshua Werner, NPS, 2020
Through the Looking Glass: Classifying Anomalous BGP Communities
Joshua Welch, NPS, 2020
The Earth is not a Sphere: On the Geographic Alignment of Autonomous Systems
Kamil Balitzki, TU Berlin, 2019
Re-evaluating the AS-level Multi-Tier Model
Lars Prehn, TU Berlin, 2018
On Inferring Primary AS Paths from BGP Routing Data
Omar Faruque, TU Berlin, 2018
Measurement and Characterization of Address Block Announcements from Different Vantage Points
Md Shihab Karim, TU Berlin, 2017
On the Potentials of Extending Conventional Measurement Tools for Network Deployments using ALTO
Johannes Schütze, TU Berlin, 2016
Measurement and Analysis of the SoShare Hybrid Server-P2P System
Li Boxuan, TU Berlin, 2016
Measuring the Indirect Prefix Delegation using Public Routing Information
Shen Jinji, TU Berlin, 2016