I am a fifth year PhD student at the Networked Systems Group (NSG) led by Prof. Dr. Laurent Vanbever. I have a background in theoretical computer science and distributed computing, with a focus on fault-tolerance. My current research interests lie in verification and synthesis of distributed network configurations.
Vita:
I received both my Bachelor's (2016) and Master’s Degree (2018) in Informatics from the Technical University of Munich, Germany. From June 2018 to August 2020, I was a researcher at the Distributed Computing Group under the supervision of Prof. Dr. Roger Wattenhofer. While I was mostly working on developing byzantine fault-tolerant systems, I have gathered additional experience in supervising student theses, as a teaching assistant and as a replacement lecturer. Until fall 2021, I was also a member of the teaching commission (UK) of the D-ITET departement of ETH. From September 2020, my research focus moved towards networking, covering projects on trust in programmable networks and transient network verification & synthesis.
BibTeX...
Tobias Bühler, Roland Schmid, Sandro Lutz, Laurent Vanbever
ACM HotNets 2022. Austin, Texas, USA (November 2022).
In theory, any network operator, developer, or vendor should have access to large amounts of live network traffic for testing their solutions. In practice, though, that is not the case. Network actors instead have to use packet traces or synthetic traffic, which is highly suboptimal: today's generated traffic is unrealistic. We propose a system for generating live application traffic leveraging massive codebases such as GitHub.
Our key observation is that many repositories have now become "orchestrable" thanks to the rise of container technologies. To showcase the practicality of the approach, we iterate through >293k GitHub repositories and manage to capture >74k traces containing meaningful and diverse network traffic. Based on this first success, we outline the design of a system, DYNAMO, which analyzes these traces to select and orchestrate open-source projects to automatically generate live application traffic matching a user's specification.
Tibor Schneider, Roland Schmid, Laurent Vanbever
IEEE ICNP 2022. Lexington, KY, USA (November 2022).
Configuration Synthesis promises to increase automation in network hardware configuration but is generally assumed to constitute a computationally hard problem. We conduct a formal analysis of the computational complexity of network-wide Configuration Synthesis to establish this claim formally. To that end, we consider Configuration Synthesis as a decision problem, whether or not the selected routing protocol(s) can implement a given set of forwarding properties.
We find the complexity of Configuration Synthesis heavily depends on the combination of the forwarding properties that need to be implemented in the network, as well as the employed routing protocol(s). Our analysis encompasses different forwarding properties that can be encoded as path constraints, and any combination of distributed destination-based hop-by-hop routing protocols. Many of these combinations yield NP-hard Configuration Synthesis problems; in particular, we show that the satisfiability of a set of arbitrary waypoints for any hop-by-hop routing protocol is NP-complete. Other combinations, however, show potential for efficient, scalable Configuration Synthesis.
Max Mathys, Roland Schmid, Jakub Sliwinski, Roger Wattenhofer
6th International Workshop on Cryptocurrencies and Blockchain Technology (CBT). Copenhagen, Denmark (September 2022).
We present Accept, a simple, asynchronous transaction system that achieves perfect horizontal scaling.
Usual blockchain-based transaction systems come with a fundamental throughput limitation as they require that all (potentially unrelated) transactions must be totally ordered. Such solutions thus require serious compromises or are outright unsuitable for large-scale applications, such as global retail payments.
Accept provides efficient horizontal scaling without any limitation. To that end, Accept satisfies a relaxed form of consensus and does not establish an ordering of unrelated transactions. Furthermore, Accept achieves instant finality and does not depend on a source of randomness.
Pál András Papp, Valentin Stoppiello, Roland Schmid, Roger Wattenhofer
arXiv CoRR 2021. (August 2021).
This paper introduces the Two-Class (r,k)-Coloring problem: Given a fixed number of k colors, such that only r of these k colors allow conflicts, what is the minimal number of conflicts incurred by an optimal coloring of the graph?
We establish that the family of Two-Class (r,k)-Coloring problems is NP-complete for any $k \geq 2$ when $(r, k) \neq (0,2)$. Furthermore, we show that Two-Class (r,k)-Coloring for $k \geq 2$ colors with one (r = 1) relaxed color cannot be approximated to any constant factor ($\notin$ APX).
Finally, we show that Two-Class (r,k)-Coloring with $k \geq r \geq 2$ colors is APX-complete.
Zeta Avarikioti, Lioba Heimbach, Roland Schmid, Laurent Vanbever, Roger Wattenhofer, Patrick Wintermeyer
arXiv CoRR 2020. (September 2020).
We introduce FnF-BFT, a parallel-leader byzantine fault-tolerant state-machine replication protocol for the partially synchronous model with theoretical performance bounds during synchrony. By allowing all replicas to act as leaders and propose requests independently, FnF-BFT parallelizes the execution of requests. Leader parallelization distributes the load over the entire network – increasing throughput by overcoming the single-leader bottleneck. We further use historical data to ensure that well-performing replicas are in command. FnF-BFT's communication complexity is linear in the number of replicas during synchrony and thus competitive with state-of-the-art protocols. Finally, with FnF-BFT, we introduce the first BFT protocol with performance guarantees in stable network conditions under truly byzantine attacks. A prototype implementation of FnF-BFT outperforms (state-of-the-art) HotStuff's throughput, especially as replicas increase, showcasing FnF-BFT's significantly improved scaling capabilities.
Manuel Eichelberger, David Geiter, Roland Schmid, Roger Wattenhofer
IEEE ITSC 2020. Rhodes, Greece (September 2020).
Hyperloop pods are expected to travel faster than 1,000 km/h. Apart from high speed, high throughput and low latency are crucial to hyperloop's success. We show that hyperloop networks have the potential to transport as many passengers as train or plane networks. Our on-demand pod scheduling method provides low passenger waiting times of only a few minutes, even at peak times. That minimizes the overall trip latencies. Further, our scheduling results in low resource usage in terms of consumed energy and required number of pods in the system.
With on-demand scheduling, passengers need not look up schedules and cannot miss connections. Rather, the schedule follows passengers' itineraries. In addition, the hyperloop concept can enable many direct connections due to small pod capacities.
We conclude that hyperloop systems have the potential to become the preferred mode of transportation by being fast, reducing waiting times and keeping up with high demand -- all while offering more convenience than current public transportation.
Roland Schmid, Roger Wattenhofer
arXiv CoRR 2019. (June 2019).
PermitBFT establishes a permissioned byzantine ledger in the partially synchronous networking model. For n replicas, PermitBFT tolerates up to f < n/3 byzantine replicas. It is the first BFT protocol to achieve a latency of just 2 message delays despite tolerating byzantine replicas throughout the “fast track”, as long as they are not the leader. The design of PermitBFT relies on two fundamental concepts. First, in PermitBFT the participating nodes do not wait for a distinguished leader to act and subsequently confirm its actions, but send permits to the next leader proactively. Second, PermitBFT achieves a separation of the decision powers that are usually concentrated on a single leader node. A leader in PermitBFT controls which transactions to include in a new block, but not where to append the block in the block graph.
BibTeX...
Georg Schwan
Supervisors: Roland Schmid, Tibor Schneider, Prof. Laurent Vanbever
Hande Harputluoglu
Supervisors: Roland Schmid, Tobias Bühler, Dr. Georgia Fragkouli, Prof. Laurent Vanbever
Hande Harputluoglu
Supervisors: Tobias Bühler, Roland Schmid, Prof. Laurent Vanbever
Maximilian Stabel
Supervisors: Roland Schmid, Tibor Schneider, Prof. Laurent Vanbever
Kaishuo Zhang
Supervisors: Roland Schmid, Prof. Laurent Vanbever
Sandro Lutz
Supervisors: Tobias Bühler, Roland Schmid, Prof. Laurent Vanbever
Dominic Bieri
Supervisors: Roland Schmid, Prof. Laurent Vanbever
Zhengqing Liu
Supervisors: Dr. Romain Jacob, Roland Schmid, Prof. Laurent Vanbever
Patrick Wintermeyer
Supervisors: Zeta Avarikioti, Roland Schmid, Prof. Roger Wattenhofer
Max Mathys
Supervisors: Roland Schmid, Jakub Sliwinski, Prof. Roger Wattenhofer
Tobias Margiani
Supervisors: Roland Schmid, Prof. Roger Wattenhofer
Lioba Heimbach
Supervisors: Roland Schmid, Zeta Avarikioti, Prof. Roger Wattenhofer
Shoma Mori
Supervisors: Roland Schmid, Jakub Sliwinski, Prof. Roger Wattenhofer
Lukas Schmid
Supervisors: Roland Schmid, Pankaj Khanchandani, Prof. Roger Wattenhofer
Noe Heim
Supervisors: Simon Tanner, Roland Schmid, Prof. Roger Wattenhofer
Thomas Filippo Tavares Marinho, Mark Vero
Supervisors: Roland Schmid, Prof. Roger Wattenhofer
Lucas Bettua
Supervisors: Zeta Avarikioti, Roland Schmid, Prof. Roger Wattenhofer
Noah Studach
Supervisors: Simon Tanner, Roland Schmid, Prof. Roger Wattenhofer
David Geiter
Supervisors: Manuel Eichelberger, Roland Schmid, Prof. Roger Wattenhofer
Starkadur Hrobjartsson
Supervisors: Manuel Eichelberger, Roland Schmid, Prof. Roger Wattenhofer
Valentin Stoppiello
Supervisors: Pál András Papp, Roland Schmid, Prof. Roger Wattenhofer
Sibylle Jeker
Supervisors: Manuel Eichelberger, Roland Schmid, Prof. Roger Wattenhofer
Anton Brucherseifer
Supervisors: Roland Schmid, Simon Tanner, Prof. Roger Wattenhofer
Lukas Bieri
Supervisors: Zeta Avarikioti, Roland Schmid, Prof. Roger Wattenhofer
Peter Müller
Supervisors: Roland Schmid, Gino Brunner, Prof. Roger Wattenhofer