Lars Prehn

Lars Prehn

Address: Max-Planck-Institut für Informatik
Saarland Informatics Campus
Campus E1 4
66123 Saarbrücken
Location: E1 4 - 529
Phone: +49 681 9325 3532
Fax: +49 681 9325 5719
E-mail: Get email via email

Personal Information

Hobbies

My girlfriend and I take care of a young Shiba Inu lady :)
I absolutely love TED talks.
I do have a strong interest in "cardistry" and the craft of performing coin and card magic. I also do own a small collection of rare playing cards.
I used to play table tennis. However, at the moment I do play only on an occasionally basis.

Links

Out of all the talks I heared over the last couple of years the following definitively deserves to be linked:
Omid Scheybani - Breaking the Habit of Smalltalk

For more information, please visit my personal homepage.

Publications

2022

Sediqi, Z., Prehn, L., & Gasser, O. (2022). Hyper-Specific Prefixes: Gotta Enjoy the Little Things in Interdomain Routing. ACM SIGCOMM Computer Communication Review, 52(2). doi:10.1145/3544912.3544916

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@article{Sediqi22, TITLE = {Hyper-Specific Prefixes: {G}otta Enjoy the Little Things in Interdomain Routing}, AUTHOR = {Sediqi, Zubair and Prehn, Lars and Gasser, Oliver}, LANGUAGE = {eng}, DOI = {10.1145/3544912.3544916}, PUBLISHER = {ACM}, ADDRESS = {New York, NY}, YEAR = {2022}, MARGINALMARK = {$\bullet$}, JOURNAL = {ACM SIGCOMM Computer Communication Review}, VOLUME = {52}, NUMBER = {2}, PAGES = {20--34}, }

Endnote

%0 Journal Article %A Sediqi, Zubair %A Prehn, Lars %A Gasser, Oliver %+ Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society %T Hyper-Specific Prefixes: Gotta Enjoy the Little Things in Interdomain Routing : %G eng %U http://hdl.handle.net/21.11116/0000-000A-C0DF-2 %R 10.1145/3544912.3544916 %7 2022 %D 2022 %J ACM SIGCOMM Computer Communication Review %V 52 %N 2 %& 20 %P 20 - 34 %I ACM %C New York, NY

Prehn, L., Lichtblau, F., Dietzel, C., & Feldmann, A. (2022). Peering Only? Analyzing the Reachability Benefits of Joining Large IXPs Today. In Passive and Active Measurement (PAM 2022). Virtual Event: Springer. doi:10.1007/978-3-030-98785-5_15

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@inproceedings{Prehn_PAM2022, TITLE = {Peering Only? {A}nalyzing the Reachability Benefits of Joining Large {IXP}s Today}, AUTHOR = {Prehn, Lars and Lichtblau, Franziska and Dietzel, Christoph and Feldmann, Anja}, LANGUAGE = {eng}, ISBN = {978-3-030-98784-8}, DOI = {10.1007/978-3-030-98785-5_15}, PUBLISHER = {Springer}, YEAR = {2022}, MARGINALMARK = {$\bullet$}, DATE = {2022}, BOOKTITLE = {Passive and Active Measurement (PAM 2022)}, EDITOR = {Hohlfeld, Oliver and Moura, Giovane and Pelsser, Cristel}, PAGES = {338--366}, SERIES = {Lecture Notes in Computer Science}, VOLUME = {13210}, ADDRESS = {Virtual Event}, }

Endnote

%0 Conference Proceedings %A Prehn, Lars %A Lichtblau, Franziska %A Dietzel, Christoph %A Feldmann, Anja %+ Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society %T Peering Only? Analyzing the Reachability Benefits of Joining Large IXPs Today : %G eng %U http://hdl.handle.net/21.11116/0000-000A-28C0-0 %R 10.1007/978-3-030-98785-5_15 %D 2022 %B 23rd Annual Passive and Active Measurement Conference %Z date of event: 2022-03-28 - 2022-03-30 %C Virtual Event %B Passive and Active Measurement %E Hohlfeld, Oliver; Moura, Giovane; Pelsser, Cristel %P 338 - 366 %I Springer %@ 978-3-030-98784-8 %B Lecture Notes in Computer Science %N 13210

Prehn, L., Foremski, P., & Gasser, O. (2022). Kirin: Hitting the Internet with Millions of Distributed IPv6 Announcements.

(arXiv: 2210.10676)

Abstract

The Internet is a critical resource in the day-to-day life of billions of users. To support the growing number of users and their increasing demands, operators have to continuously scale their network footprint -- e.g., by joining Internet Exchange Points -- and adopt relevant technologies -- such as IPv6. IPv6, however, has a vastly larger address space compared to its predecessor, which allows for new kinds of attacks on the Internet routing infrastructure. In this paper, we present Kirin: a BGP attack that sources millions of IPv6 routes and distributes them via thousands of sessions across various IXPs to overflow the memory of border routers within thousands of remote ASes. Kirin's highly distributed nature allows it to bypass traditional route-flooding defense mechanisms, such as per-session prefix limits or route flap damping. We analyze the theoretical feasibility of the attack by formulating it as a Integer Linear Programming problem, test for practical hurdles by deploying the infrastructure required to perform a small-scale Kirin attack using 4 IXPs, and validate our assumptions via BGP data analysis, real-world measurements, and router testbed experiments. Despite its low deployment cost, we find Kirin capable of injecting lethal amounts of IPv6 routes in the routers of thousands of ASes.

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@online{Prehn2210.10676, TITLE = {Kirin: Hitting the Internet with Millions of Distributed {IPv6} Announcements}, AUTHOR = {Prehn, Lars and Foremski, Pawel and Gasser, Oliver}, LANGUAGE = {eng}, EPRINT = {2210.10676}, EPRINTTYPE = {arXiv}, YEAR = {2022}, MARGINALMARK = {$\bullet$}, ABSTRACT = {The Internet is a critical resource in the day-to-day life of billions of users. To support the growing number of users and their increasing demands, operators have to continuously scale their network footprint -- e.g., by joining Internet Exchange Points -- and adopt relevant technologies -- such as IPv6. IPv6, however, has a vastly larger address space compared to its predecessor, which allows for new kinds of attacks on the Internet routing infrastructure. In this paper, we present Kirin: a BGP attack that sources millions of IPv6 routes and distributes them via thousands of sessions across various IXPs to overflow the memory of border routers within thousands of remote ASes. Kirin's highly distributed nature allows it to bypass traditional route-flooding defense mechanisms, such as per-session prefix limits or route flap damping. We analyze the theoretical feasibility of the attack by formulating it as a Integer Linear Programming problem, test for practical hurdles by deploying the infrastructure required to perform a small-scale Kirin attack using 4 IXPs, and validate our assumptions via BGP data analysis, real-world measurements, and router testbed experiments. Despite its low deployment cost, we find Kirin capable of injecting lethal amounts of IPv6 routes in the routers of thousands of ASes. }, }

Endnote

%0 Report %A Prehn, Lars %A Foremski, Pawel %A Gasser, Oliver %+ Internet Architecture, MPI for Informatics, Max Planck Society External Organizations Internet Architecture, MPI for Informatics, Max Planck Society %T Kirin: Hitting the Internet with Millions of Distributed IPv6 Announcements : %G eng %U http://hdl.handle.net/21.11116/0000-000C-1816-1 %D 2022 %X The Internet is a critical resource in the day-to-day life of billions of users. To support the growing number of users and their increasing demands, operators have to continuously scale their network footprint -- e.g., by joining Internet Exchange Points -- and adopt relevant technologies -- such as IPv6. IPv6, however, has a vastly larger address space compared to its predecessor, which allows for new kinds of attacks on the Internet routing infrastructure. In this paper, we present Kirin: a BGP attack that sources millions of IPv6 routes and distributes them via thousands of sessions across various IXPs to overflow the memory of border routers within thousands of remote ASes. Kirin's highly distributed nature allows it to bypass traditional route-flooding defense mechanisms, such as per-session prefix limits or route flap damping. We analyze the theoretical feasibility of the attack by formulating it as a Integer Linear Programming problem, test for practical hurdles by deploying the infrastructure required to perform a small-scale Kirin attack using 4 IXPs, and validate our assumptions via BGP data analysis, real-world measurements, and router testbed experiments. Despite its low deployment cost, we find Kirin capable of injecting lethal amounts of IPv6 routes in the routers of thousands of ASes. %K Computer Science, Networking and Internet Architecture, cs.NI

2021

Prehn, L., & Feldmann, A. (2021). How Biased is our Validation (Data) for AS Relationships? In IMC ’21, ACM Internet Measurement Conference. Virtual Event, USA: ACM. doi:10.1145/3487552.3487825

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@inproceedings{Prehn_IMC21, TITLE = {How Biased is our Validation (Data) for {AS} Relationships?}, AUTHOR = {Prehn, Lars and Feldmann, Anja}, LANGUAGE = {eng}, ISBN = {978-1-4503-9129-0}, DOI = {10.1145/3487552.3487825}, PUBLISHER = {ACM}, YEAR = {2021}, MARGINALMARK = {$\bullet$}, BOOKTITLE = {IMC '21, ACM Internet Measurement Conference}, PAGES = {612--620}, ADDRESS = {Virtual Event, USA}, }

Endnote

%0 Conference Proceedings %A Prehn, Lars %A Feldmann, Anja %+ Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society %T How Biased is our Validation (Data) for AS Relationships? : %G eng %U http://hdl.handle.net/21.11116/0000-0009-7426-A %R 10.1145/3487552.3487825 %D 2021 %B ACM Internet Measurement Conference %Z date of event: 2021-11-02 - 2021-11-04 %C Virtual Event, USA %B IMC '21 %P 612 - 620 %I ACM %@ 978-1-4503-9129-0

2020

Prehn, L., Lichtblau, F., & Feldmann, A. (2020). When Wells Run Dry: The 2020 IPv4 Address Market. In CoNEXT’20, 16th International Conference on Emerging Networking Experiments And Technologies. Barcelona, Spain (Virtual Event): ACM. doi:10.1145/3386367.3431301

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@inproceedings{Prehn_CoNEXT2020, TITLE = {When wells run dry: the 2020 {IPv4} address market}, AUTHOR = {Prehn, Lars and Lichtblau, Franziska and Feldmann, Anja}, LANGUAGE = {eng}, ISBN = {9781450379489}, DOI = {10.1145/3386367.3431301}, PUBLISHER = {ACM}, YEAR = {2020}, BOOKTITLE = {CoNEXT'20, 16th International Conference on Emerging Networking Experiments And Technologies}, EDITOR = {Han, Dongsu and Feldmann, Anja}, PAGES = {46--54}, ADDRESS = {Barcelona, Spain (Virtual Event)}, }

Endnote

%0 Conference Proceedings %A Prehn, Lars %A Lichtblau, Franziska %A Feldmann, Anja %+ Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society Internet Architecture, MPI for Informatics, Max Planck Society %T When Wells Run Dry: The 2020 IPv4 Address Market : %G eng %U http://hdl.handle.net/21.11116/0000-0007-853A-2 %R 10.1145/3386367.3431301 %D 2020 %B 16th International Conference on Emerging Networking Experiments And Technologies %Z date of event: 2020-12-01 - 2020-12-04 %C Barcelona, Spain (Virtual Event) %B CoNEXT'20 %E Han, Dongsu; Feldmann, Anja %P 46 - 54 %I ACM %@ 9781450379489

Marcos, P., Prehn, L., Leal, L., Dainotti, A., Feldmann, A., & Barcellos, M. (2020). AS-Path Prepending: There is No Rose without a Thorn. In IMC ’20, 20th ACM Internet Measurement Conference. Virtual Event, USA: ACM. doi:10.1145/3419394.3423642

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@inproceedings{Marcos_IMC2020, TITLE = {{AS-Path Prepending}: {T}here is No Rose without a Thorn}, AUTHOR = {Marcos, Pedro and Prehn, Lars and Leal, Lucas and Dainotti, Alberto and Feldmann, Anja and Barcellos, Marinho}, LANGUAGE = {eng}, ISBN = {9-781-4503-8138-3}, DOI = {10.1145/3419394.3423642}, PUBLISHER = {ACM}, YEAR = {2020}, DATE = {2020}, BOOKTITLE = {IMC '20, 20th ACM Internet Measurement Conference}, PAGES = {506--520}, ADDRESS = {Virtual Event, USA}, }

Endnote

%0 Conference Proceedings %A Marcos, Pedro %A Prehn, Lars %A Leal, Lucas %A Dainotti, Alberto %A Feldmann, Anja %A Barcellos, Marinho %+ External Organizations Internet Architecture, MPI for Informatics, Max Planck Society External Organizations External Organizations Internet Architecture, MPI for Informatics, Max Planck Society External Organizations %T AS-Path Prepending: There is No Rose without a Thorn : %G eng %U http://hdl.handle.net/21.11116/0000-0007-854C-E %R 10.1145/3419394.3423642 %D 2020 %B 20th ACM Internet Measurement Conference %Z date of event: 2020-10-27 - 2020-10-29 %C Virtual Event, USA %B IMC '20 %P 506 - 520 %I ACM %@ 9-781-4503-8138-3

Research Interests

At some point I maintained a list of topics; however, it grew to the point where keeping it became sort of meaningless.
Yet, my current situation is ridiculously easy to explain: regardless of the topic, if an idea piques my interest I'm in on it.

Reviewing Activity & Workshop / Conference positions

Student scribe for the CoNEXT 2020 TPC meeting

Teachings

Teachings for MPI INET:

Summer Term 2020: Data Networks online course (Administration; tutoring)
Winter Term 2020/2021: Hot Topics in Data Networks Seminar (Administration; tutoring & supervision of participating students)

I have been a Tutor for the following courses at Technische Universität Berlin:

Summer Term 2016: Algorithms and Datastructures
Winter Term 2016: Communication Networks
Summer Term 2017: Algorithms and Datastructures
Winter Term 2017: Network Protocols and Algorithms
Winter Term 2018: Network Protocols and Algorithms

Recent Positions

November 2018 - now:
PhD-Student at MPI in Saarbrücken

November 2017 - October 2018:
student worker with research tasks at Technische Universität Berlin in Berlin

April 2016 - October 2017:
student worker with teaching tasks at Technische Universität Berlin in Berlin

October 2014 - March 2016:
student worker in the field of data acquisition at TEAS Germany GmbH in Berlin

Education

November 2018 - present:
Ph. D. student in Computer Science at the Universität des Saarlandes, Saarbrücken, Germany and the Max-Planck-Institut für Informatik

My current research focuses on the quality of publicly available data sources to reveal the Internet's logical structure as well as the mapping of this logical structure onto physical infrastructure. Apart from that I'm also interested in topics regarding route propagation, congestion inference, and content delivery.

November 2017 - October 2018:
Master in Computer Science at the technische Universität Berlin

Starting from October 2017 I pursued my master's degree in Computer Science at the Technische Universität Berlin. Since I developed a special interest in networks during my bachelor degree I choose 'Distributed Systems and Networks' as my major subject. The accompanying courses gave me the chance to better understand the full specturm of building blocks that today's Internet consists of; I learned about the Internet's control plane - which is where my interest for interdomain routing as well as congestion identification started from, the business related aspects that drove its current evolution, as well as how to configure the hardware that it runs on. To complement my theoretical knowledge I took projects that were closely related to research topics that reflected my interests. In one of those projects I analyzed the difference in congestion singals that can be derived from both explicit and implicit - RTT - signals. In my master thesis I collected Internet topology data from various sources, analyzed their individual contribution, and evaluated different methods for inferring the Internet hierarchies top. After a year of study I received my master's degree in October 2018 with a final grade of 1.0.

October 2014 - March 2018:
Bachelor in Computer Science at the technische Universität Berlin

August 2008 - August 2014:
Abitur at the Strittmatter Gymnasium Gransee in Gransee