Distributed Systems

Distributed systems consist of multiple independent components that are connected by a network and provide a common service. Depending on the particular use case, this includes deployments in which a collection of small data sets is distributed among a few nodes, as well as architectures for the massively parallelized processing of large workloads in the context of cloud applications. While on the one hand the distribution of a system offers new opportunities, for example the improvement of fault-tolerance properties through replication of data and computations, on the other hand it also creates additional challenges such as the need for an efficient implementation of services when several geographic sites are involved. A key goal of this group's research activities is the development of concepts and techniques that enable systems to leverage the advantages associated with distribution and at the same time use the available resources as efficiently as possible.

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Term: 1. September 2022 - 31. August 2024
Funding source: Bundesministerium für Wirtschaft und Klimaschutz (BMWK)
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Das Konzept von Distributed Ledger Systemen (Blockchain) ist eine grundlegend neue Basistechnologie, welche in der öffentlichen Wahrnehmung derzeit verstärkt im Fokus steht und welche erhöhtes Potential zur Lösung von Problemstellungen in einer Vielzahl von Anwendungsbereichen verspricht.

Daneben wandelt sich die Luftverkehrslandschaft absehbar mit einer massiven Zunahme an Luftverkehrsteilnehmern und weiteren Luftverkehrsarten wie autonomen Kleinstsystemen. Des Weiteren besteht ein…

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Term: 1. September 2022 - 1. September 2025
Funding source: Deutsche Forschungsgemeinschaft (DFG)
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Distributed Ledger Technologies (DLTs), often referred to as blockchains, enable the realisation of reliable and attack-resilient services without a central infrastructure. However, the widely used proof-of-work mechanisms for DLTs suffer from high latencies of operations and enormous energy costs. Byzantine fault-tolerant (BFT) consensus protocols prove to be a potentially energy-efficient alternative to proof-of-work. However, current BFT protocols also present challenges that still limit their practical use in production systems. This research project addresses these challenges by (1) improving the scalability of BFT consensus protocols without reducing their resilience, (2) applying modelling approaches for making the expected performance and timing behaviour of these protocols more predictable, even under attacks, taking into consideration environmental conditions, and (3) supporting the design process for valid, automated testable BFT systems from specification to deployment in a blockchain infrastructure. The topic of scalability aims at finding practical solutions that take into account challenges such as recovery from major outages or upgrades, as well as reconfigurations at runtime. We also want to design a resilient communication layer that decouples the choice of a suitable communication topology from the actual BFT consensus protocol and thus reduces its complexity.This should be supported by the use of trusted hardware components. In addition, we want to investigate combinations of these concepts with suitable cryptographic primitives to further improve scalability. Using systematic modelling techniques, we want to be able to analyse the efficiency of scalable, complex BFT protocols (for example, in terms of throughput and latency of operations), already before deploying them in a real environment, based on knowledge of system size, computational power of nodes, and basic characteristics of the communication links. We also want to investigate robust countermeasures that help defending against targeted attacks in large-scale blockchain systems. The third objective is to support the systematic and valid implementation in a practical system, structured into a constructive, modular approach, in which a validatable BFT protocol is assembled based on smaller, validatable building blocks; the incorporation of automated test procedures based on a heuristic algorithm which makes the complex search space of misbehaviour in BFT systems more manageable; and a tool for automated deployment with accompanying benchmarking and stress testing in large-scale DLTs.

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Term: 1. November 2024 - 31. October 2027
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
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Network-based services such as distributed databases, file systems, or blockchains are essential parts of today's computing infrastructures and therefore must be able to withstand a wide spectrum of fault scenarios, including hardware crashes, software failures, and attacks. Although a variety of state-machine replication protocols exist that provide fault and intrusion tolerance, it is inherently difficult to build dependable systems based on their complex and often incomplete specifications.…

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Term: 1. January 2018 - 31. December 2026
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The processing of large amounts of data on distributed execution platforms such as MapReduce or Heron contributes significantly to the energy consumption of today's data centers. The E³ project aims at minimizing the power consumption of such execution environments without sacrificing performance. For this purpose, the project develops means to make execution environments and data-processing platforms energy aware and to enable them to exploit knowledge about applications to dynamically adapt …

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Term: 1. January 2012 - 31. December 2026
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Coordination services such as ZooKeeper are essential building blocks of today's data-center infrastructures as they provide processes of distributed applications with means to exchange messages, to perform leader election, to detect machine or process crashes, or to reliably store configuration data. Providing an anchor of trust for their client applications, coordination services have to meet strong requirements regarding stability and performance. Only this way, it is possible to ensure that…

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Term: 1. October 2009 - 31. October 2024
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
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Internet-based services play a central role in today's society. With such services progressively taking over from traditional infrastructures, their complexity steadily increases. On the downside, this leads to more and more faults occurring. As improving software-engineering techniques alone will not do the job, systems have to be prepared to tolerate faults and intrusions.

REFIT investigates how systems can provide fault and intrusion tolerance in a resource-efficient manner. The key technology…

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