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Benjamin Erb

Benjamin Erb holds a Diploma degree in Computer Science in Media and a Bachelor degree in Psychology from Ulm University. He is currently employed as a research assistant at the Institute of Distributed Systems.

Research Outline: Chronograph

As part of my thesis, I am currently working on Chronograph – a novel graph computing platform that combines concepts of traditional graph computing with features from event-driven architectures. The platform combines a vertex-based programming model, an asynchronous concurrency model using message passing, and an alternative persistence approach that is based on event sourcing.

Research Interests 

  • Distributed Computing
    • Graph-based computing
    • Event processing
    • Distribution and parallelization aspects
    • Time & programming models
  • Distributed systems & architectures
    • Event-driven architectures
    • Event sourcing & CQRS
    • Scalability of architectures
    • Concurrency and parallelism
  • Other Topics
    • Psychology & Privacy
    • Web technologies & web architectures
    • Programming languages and concepts
    • Open data


  • SIDGRAPH (started 2014/08 – 2017/07; completed): Development of scalability and distribution mechanisms for graph-based and event-driven computations and simulations
  • PRIPARE (2013/10 – 2015/09; completed): Design and implementation of a collaborative web portal for patterns and best practices for privacy
  • diretto / diretto.resc (2009/10 – 2011/08; completed): The main target of this student project has been the design and prototypical implementation of a platform for distributed reporting. Use cases include collaborations in disaster scenarios and the live coverage of large-scale public events. The second stage of the project has been funded by MFG Stiftung Baden-Württemberg as part of a Karl-Steinbuch scholarship.



Bendig, Eileen; Erb, Benjamin; Schulze-Thuesing, Lea; Baumeister, Harald
Next Generation: Chatbots in Clinical Psychology and Psychotherapy to Foster Mental Health – A Scoping Review
März 2019

Zusammenfassung: Background and Purpose: The present age of digitalization brings with it progress and new possibilities for health care in general and clinical psychology/psychotherapy in particular. Internet- and mobile-based interventions (IMIs) have often been evaluated. A fully automated version of IMI are chatbots. Chatbots are automated computer programs that are able to hold, e.g., a script-based conversation with a human being. Chatbots could contribute to the extension of health care offers. The aim of this review is to conceptualize the scope and to work out the current state of the art of chatbots fostering mental health. Methods: The present article is a scoping review on chatbots in clinical psychology and psychotherapy. Studies that utilized chatbots to foster mental health were included. Results: The technology of chatbots is still experimental in nature. Studies are most often pilot studies by nature. The field lacks high-quality evidence derived from randomized controlled studies. Results with regards to practicability, feasibility, and acceptance of chatbots to foster mental health are promising but not yet directly transferable to psychotherapeutic contexts. Discussion: The rapidly increasing research on chatbots in the field of clinical psychology and psychotherapy requires corrective measures. Issues like effectiveness, sustainability, and especially safety and subsequent tests of technology are elements that should be instituted as a corrective for future funding programs of chatbots in clinical psychology and psychotherapy.

Bendig, Eileen; Erb, Benjamin; Meißner, Dominik; Hannaby, Bronte; Baumeister, Harald
Chatbots and mental health: Current advances in software agents providing psychological interventions and results from a pretest-posttest feasibility trial on the software agent 'SISU' (Abstract)
International Society for Research on Internet Interventions 10th Conference
Februar 2019


Lukaseder, Thomas; Stölzle, Kevin; Kleber, Stephan; Erb, Benjamin; Kargl, Frank
An SDN-based Approach For Defending Against Reflective DDoS Attacks
Proceedings of the 43rd IEEE Conference on Local Computer Networks
Oktober 2018

Zusammenfassung: Distributed Reflective Denial of Service (DRDoS) attacks are an immanent threat to Internet services. The potential scale of such attacks became apparent in March 2018 when a memcached-based attack peaked at 1.7 Tbps. Novel services built upon UDP increase the need for automated mitigation mechanisms that react to attacks without prior knowledge of the actual application protocols used. With the flexibility that software-defined networks offer, we developed a new approach for defending against DRDoS attacks; it not only protects against arbitrary DRDoS attacks but is also transparent for the attack target and can be used without assistance of the target host operator. The approach provides a robust mitigation system which is protocol-agnostic and effective in the defense against DRDoS attacks.

Lukaseder, Thomas; Maile, Lisa; Erb, Benjamin; Kargl, Frank
SDN-Assisted Network-Based Mitigation of Slow DDoS Attacks
August 2018

Zusammenfassung: Slow-running attacks against network applications are often not easy to detect, as the attackers behave according to the specification. The servers of many network applications are not prepared for such attacks, either due to missing countermeasures or because their default configurations ignores such attacks. The pressure to secure network services against such attacks is shifting more and more from the service operators to the network operators of the servers under attack. Recent technologies such as software-defined networking offer the flexibility and extensibility to analyze and influence network flows without the assistance of the target operator. Based on our previous work on a network-based mitigation, we have extended a framework to detect and mitigate slow-running DDoS attacks within the network infrastructure, but without requiring access to servers under attack. We developed and evaluated several identification schemes to identify attackers in the network solely based on network traffic information. We showed that by measuring the packet rate and the uniformity of the packet distances, a reliable identificator can be built, given a training period of the deployment network.

Erb, Benjamin; Meißner, Dominik; Steer, Benjamin A.; Margan, Domagoj; Kargl, Frank; Cuadrado, Felix; Pietzuch, Peter
GraphTides: A Framework for Evaluating Stream-based Graph Processing Platforms
Proceedings of the 1st Joint International Workshop on Graph Data Management Experiences & Systems (GRADES) and Network Data Analytics (NDA)
Juni 2018

Zusammenfassung: Stream-based graph systems continuously ingest graph-changing events via an established input stream, performing the required computation on the corresponding graph. While there are various benchmarking and evaluation approaches for traditional, batch-oriented graph processing systems, there are no common procedures for evaluating stream-based graph systems. We, therefore, present GraphTides, a generic framework which includes the definition of an appropriate system model, an exploration of the parameter space, suitable workloads, and computations required for evaluating such systems. Furthermore, we propose a methodology and provide an architecture for running experimental evaluations. With our framework, we hope to systematically support system development, performance measurements, engineering, and comparisons of stream-based graph systems.

Meißner, Dominik; Erb, Benjamin; Kargl, Frank; Tichy, Matthias
retro-λ: An Event-sourced Platform for Serverless Applications with Retroactive Computing Support
Proceedings of the 12th ACM International Conference on Distributed Event-Based Systems
Juni 2018

Zusammenfassung: State changes over time are inherent characteristics of stateful applications. So far, there are almost no attempts to make the past application history programmatically accessible or even modifiable. This is primarily due to the complexity of temporal changes and a difficult alignment with prevalent programming primitives and persistence strategies. Retroactive computing enables powerful capabilities though, including computations and predictions of alternate application timelines, post-hoc bug fixes, or retroactive state explorations. We propose an event-driven programming model that is oriented towards serverless computing and applies retroaction to the event sourcing paradigm. Our model is deliberately restrictive, but therefore keeps the complexity of retroactive operations in check. We then introduce retro-λ, a runtime platform that implements the model and provides retroactive capabilites to its applications. While retro-λ only shows negligible performance overheads compared to similar solutions for running regular applications, it enables its users to execute retroactive computations on the application histories as part of its programming model.

Meißner, Dominik; Erb, Benjamin; Kargl, Frank
Poster: Performance Engineering in Distributed Event-sourced Systems
Proceedings of the 12th ACM International Conference on Distributed Event-Based Systems
Juni 2018

Zusammenfassung: Distributed event-sourced systems adopt a fairly new architectural style for data-intensive applications that maintains the full history of the application state. However, the performance implications of such systems are not yet well explored, let alone how the performance of these systems can be improved. A central issue is the lack of systematic performance engineering approaches that take into account the specific characteristics of these systems. To address this problem, we suggest a methodology for performance engineering and performance analysis of distributed event-sourced systems based on specific measurements and subsequent, targeted optimizations. The methodology blends in well into existing software engineering processes and helps developers to identify bottlenecks and to resolve performance issues. Using our structured approach, we improved an existing event-sourced system prototype and increased its performance considerably.

Erb, Benjamin; Meißner, Dominik; Ogger, Ferdinand; Kargl, Frank
Poster: Log Pruning in Distributed Event-sourced Systems
Proceedings of the 12th ACM International Conference on Distributed Event-Based Systems
Juni 2018

Zusammenfassung: Event sourcing is increasingly used and implemented in event-based systems for maintaining the evolution of application state. However, unbounded event logs are impracticable for many systems, as it is difficult to align scalability requirements and long-term runtime behavior with the corresponding storage requirements. To this end, we explore the design space of log pruning approaches suitable for event-sourced systems. Furthermore, we survey specific log pruning mechanisms for event-sourced logs. In a brief evaluation, we point out the trade-offs when applying pruning to event logs and highlight the applicability of log pruning to event-sourced systems.


Erb, Benjamin; Meißner, Dominik; Pietron, Jakob; Kargl, Frank
Chronograph – A Distributed Processing Platform for Online and Batch Computations on Event-sourced Graphs
Proceedings of the 11th ACM International Conference on Distributed Event-Based Systems
Juni 2017

Zusammenfassung: Several data-intensive applications take streams of events as a continuous input and internally map events onto a dynamic, graph-based data model which is then used for processing. The differences between event processing, graph computing, as well as batch processing and near-realtime processing yield a number of specific requirements for computing platforms that try to unify theses approaches. By combining an altered actor model, an event-sourced persistence layer, and a vertex-based, asynchronous programming model, we propose a distributed computing platform that supports event-driven, graph-based applications in a single platform. Our Chronograph platform concept enables online and offline computations on event-driven, history-aware graphs and supports different processing models on the evolving graph.

Erb, Benjamin; Meißner, Dominik; Habiger, Gerhard; Pietron, Jakob; Kargl, Frank
Consistent Retrospective Snapshots in Distributed Event-sourced Systems
Proceedings of the International Conference on Networked Systems 2017
März 2017

Zusammenfassung: An increasing number of distributed, event-based systems adopt an architectural style called event sourcing, in which entities keep their entire history in an event log. Event sourcing enables data lineage and allows entities to rebuild any previous state. Restoring previous application states is a straightforward task in event-sourced systems with a global and totally ordered event log. However, the extraction of causally consistent snapshots from distributed, individual event logs is rendered non-trivial due to causal relationships between communicating entities. High dynamicity of entities increases the complexity of such reconstructions even more. We present approaches for retrospective and global state extraction of event-sourced applications based on distributed event logs. We provide an overview on historical approaches towards distributed debugging and breakpointing, which are closely related to event log-based state reconstruction. We then introduce and evaluate our approach for non-local state extraction from distributed event logs, which is specifically adapted for dynamic and asynchronous event-sourced systems.


Erb, Benjamin; Kargl, Frank
Chronograph–A Distributed Platform for Event-Sourced Graph Computing
Proceedings of the Posters and Demos Session of the 17th International Middleware Conference
Dezember 2016

Zusammenfassung: Many data-driven applications require mechanisms for processing interconnected or graph-based data sets. Several platforms exist for offline processing of such data and fewer solutions address online computations on dynamic graphs. We combined a modified actor model, an event-sourced persistence layer, and a vertex-based, asynchronous programming model in order to unify event-driven and graph-based computations. Our distributed chronograph platform supports both near-realtime and batch computations on dynamic, event-driven graph topologies, and enables full history tracking of the evolving graphs over time.

Seybold, Daniel; Wagner, Nicolas; Erb, Benjamin; Domascka, Jörg
Is Elasticity of Scalable Databases a Myth?
4th Workshop on Scalable Cloud Data Management
Dezember 2016
Lukaseder, Thomas; Bradatsch, Leonard; Erb, Benjamin; van der Heijden, Rens W.; Kargl, Frank
A Comparison of TCP Congestion Control Algorithms in 10G Networks
Proceedings of the 41st IEEE Conference on Local Computer Networks (LCN) , Seite 706-714.
November 2016

Zusammenfassung: The increasing availability of 10G Ethernet network capabilities challenges existing transport layer protocols. As 10G connections gain momentum outside of backbone networks, the choice of appropriate TCP congestion control algorithms becomes even more relevant for networked applications running in environments such as data centers. Therefore, we provide an extensive overview of relevant TCP congestion control algorithms for high-speed environments leveraging 10G. We analyzed and evaluated six TCP variants using a physical network testbed, with a focus on the effects of propagation delay and significant drop rates. The results indicate that of the algorithms compared, BIC is most suitable when no legacy variant is present; CUBIC is suggested otherwise.

Lukaseder, Thomas; Bradatsch, Leonard; Erb, Benjamin; Kargl, Frank
Setting Up a High-Speed TCP Benchmarking Environment — Lessons Learned
Proceedings of the 41st IEEE Conference on Local Computer Networks (LCN) , Seite 160-163.
November 2016

Zusammenfassung: There are many high-speed TCP variants with different congestion control algorithms, which are designed for specific settings or use cases. Distinct features of these algorithms are meant to optimize different aspects of network performance, and the choice of TCP variant strongly influences application performance. However, setting up tests to help with the decision of which variant to use can be problematic, as many systems are not designed to deal with high bandwidths, such as 10 Gbps or more. This paper provides an overview of pitfalls and challenges of realistic network analysis to help in the decision making process.

Meißner, Dominik; Erb, Benjamin; van der Heijden, Rens W.; Lange, Kristin; Kargl, Frank
Mobile Triage Management in Disaster Area Networks Using Decentralized Replication
Proceedings of the Tenth ACM MobiCom Workshop on Challenged Networks , Seite 7-12.
Herausgeber: ACM,
Oktober 2016
ISBN: 978-1-4503-4256-8

Zusammenfassung: In large-scale disaster scenarios, efficient triage management is a major challenge for emergency services. Rescue forces traditionally respond to such incidents with a paper-based triage system, but technical solutions can potentially achieve improved usability and data availability. We develop a triage management system based on commodity hardware and software components to verify this claim. We use a single-hop, ad-hoc network architecture with multi-master replication, a tablet-based device setup and a mobile application for emergency services. We study our system in cooperation with regional emergency services and describe experiences from a field exercise. We show that state-of-the-art commodity technology provides the means necessary to implement a triage management system compatible with existing emergency service procedures, while introducing additional benefits. This work highlights that powerful real-world ad-hoc networking applications do not require unreasonable development effort, as existing tools from distributed systems, like replicating No-SQL databases, can be used successfully.

Erb, Benjamin; Habiger, Gerhard; Hauck, Franz J.
On the Potential of Event Sourcing for Retroactive Actor-based Programming
Proceedings of the 1st Workshop on Programming Models and Languages for Distributed Computing
Juli 2016

Zusammenfassung: The actor model is an established programming model for distributed applications. Combining event sourcing with the actor model allows the reconstruction of previous states of an actor. When this event sourcing approach for actors is enhanced with additional causality information, novel types of actor-based, retroactive computations are possible. A globally consistent state of all actors can be reconstructed retrospectively. Even retroactive changes of actor behavior, state, or messaging are possible, with partial recomputations and projections of changes in the past. We believe that this approach may provide beneficial features to actor-based systems, including retroactive bugfixing of applications, decoupled asynchronous global state reconstruction for recovery, simulations, and exploration of distributed applications and algorithms.

Kraft, Robin; Erb, Benjamin; Mödinger, David; Kargl, Frank
Using Conflict-Free Replicated Data Types for Serverless Mobile Social Applications
Proceedings of the 8th ACM International Workshop on Hot Topics in Planet-scale mObile computing and online Social neTworking , Seite 49-54.
Herausgeber: ACM,
Juli 2016
ISBN: 978-1-4503-4344-2

Zusammenfassung: A basic reason for backend systems in mobile application architectures is the centralized management of state. Mobile clients synchronize local states with the backend in order to maintain an up-to-date view of the application state. As not all mobile social applications require strong consistency guarantees, we survey an alternative approach using special data structures for mobile applications. These data structures only provide eventual consistency, but allow for conflict-free replication between peers. Our analysis collects the requirements of social mobile applications for being suitable for this approach. Based on exemplary mobile social applications, we also point out the benefits of serverless architecture or architectures with a thin backend layer.

Bösch, Christoph; Erb, Benjamin; Kargl, Frank; Kopp, Henning; Pfattheicher, Stefan
Tales from the Dark Side: Privacy Dark Strategies and Privacy Dark Patterns
Proceedings on Privacy Enhancing Technologies, 2016(4):237-254
Juli 2016

Zusammenfassung: Privacy strategies and privacy patterns are fundamental concepts of the privacy-by-design engineering approach. While they support a privacy-aware development process for IT systems, the concepts used by malicious, privacy-threatening parties are generally less understood and known. We argue that understanding the ``dark side'', namely how personal data is abused, is of equal importance. In this paper, we introduce the concept of privacy dark strategies and privacy dark patterns and present a framework that collects, documents, and analyzes such malicious concepts. In addition, we investigate from a psychological perspective why privacy dark strategies are effective. The resulting framework allows for a better understanding of these dark concepts, fosters awareness, and supports the development of countermeasures. We aim to contribute to an easier detection and successive removal of such approaches from the Internet to the benefit of its users.

Erb, Benjamin
Computing on Event-sourced Graphs
4th Graph-TA Workshop, Universitat Politècnica de Catalunya, Barcelona, Spain
März 2016

Zusammenfassung: While traditional graph computing usually employs batch processing, near-realtime computations on streaming data are often accomplished using event processing technologies. However, an increasing number of applications requires both computing capabilities for scenarios with highly dynamic and highly interconnected data fed by a stream of events. We suggest a novel platform architecture for graph computing that enables event-driven graph dynamicity while also supporting complex, long-running graph computations within the same system. To this end, we combine a vertex-based programming model, an asynchronous concurrency model using message passing, and an alternative persistence approach that is based on event sourcing. As a result, our approach allows for computations on dynamic live graphs as well as decoupled batch computations on graph snapshots. We also support the reconstruction of arbitrary previous graph states as well as temporal graph computations. Furthermore, our approach enables retroactive modifications of snapshot branches, so that alternate histories can be explored or future states of the graph can be simulated and predicted.


Erb, Benjamin; Kargl, Frank
A Conceptual Model for Event-sourced Graph Computing
Proceedings of the 9th ACM International Conference on Distributed Event-Based Systems aus DEBS '15 , Seite 352-355.
Herausgeber: ACM, New York, NY, USA
Juni 2015
ISBN: 978-1-4503-3286-6
Erb, Benjamin
Towards Distributed Processing on Event-sourced Graphs (Extended Abstract)
Doctoral Symposium, 9th ACM International Conference on Distributed Event-Based Systems
Juni 2015


Domaschka, Jörg; Hauser, Christopher B.; Erb, Benjamin
Reliability and Availability Properties of Distributed Database Systems
Enterprise Distributed Object Computing Conference (EDOC), 2014 18th IEEE International
September 2014
Erb, Benjamin; Kargl, Frank
Combining Discrete Event Simulations and Event Sourcing
7th International ICST Conference on Simulation Tools and Techniques, SIMUTools '14 , Seite 51-55.
August 2014
ISBN: 978-1-63190-007-5
Engelmann, Felix; Lukaseder, Thomas; Erb, Benjamin; van der Heijden, Rens W.; Kargl, Frank
Dynamic Packet-filtering in High-speed Networks Using NetFPGAs
Proceedings of the 3rd International Conference on Future Generation Communication Technology (Best Paper Award) , Seite 55-59.
Herausgeber: IEEE,
August 2014
Erb, Benjamin; Kargl, Frank; Domaschka, Jörg
Concurrent programming in web applications
it-Information Technology, 56(3):119--126
Mai 2014
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Seminars and Student Projects