Dr.-Ing. Kalman Graffi


Phone:   +49-6151-16 4959  
Location: S3|20 213

Email: Kalman.Graffi@...

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All publications of Kalman Graffi

This website is outdated - Since 2011 I am at the University of Paderborn --> Link


All publications of Kalman Graffi

Short Bio

Kalman Graffi graduated from the Technische Universität Darstadt with a PhD in electrical engineering and information technology, a diploma in computer science and a diploma in mathematics in 2006. He is in the Multimedia Communications Lab and working at KOM in the DFG funded reasearch group „QuaP2P: Improving the quality of peer-to-peer systems“. He is focusing on the monitoring and management of peer-to-peer systems as well as on peer-to-peer based online social networks.

Monitoring the quality of service of peer-to-peer systems, help commercial system providers and users to observe the behavior of the system. With an automated re-configuration approach misleading trends and quality issues can be tackled, resulting in a self-optimizing peer-to-peer network. An overview on this topic is given in www.skynet-project.com

Online social networks are very popular nowadays, however, using a peer-to-peer based approach could both benefit the system providers and users. With LifeSocial.KOM he persented an operational peer-to-peer-based prototype at the CeBIT 2009. The solution is reliable, monitored, secure and provides in addition to the typical functionalities of online social networks some collaborative elements. An overview and videos are given in www.lifesocial.org

Research Area

Monitoring and Managing Peer-to-Peer Systems

  • Monitoring and information aggregation approaches for p2p system
  • Quality management and enforcement in p2p systems
  • Engineering of reliable multi-purpose p2p-platforms
  • Modeling and standardization of functional layers in peer-to-peer systems
  • General efficiency-centric mechanisms and approaches in peer-to-peer systems
  • Scheduling and task priorization in self-managing autonomous distributed systems

Peer-to-Peer-based Social Online Networks

  • Reliable and efficient distributed data storage
  • Quality management and enforcement in p2p systems
  • Engineering of reliable multi-purpose p2p-platforms
  • Modeling of functional layers in peer-to-peer systems and applied data mining
  • General efficiency-centric mechanisms and approaches in peer-to-peer systems
  • Scheduling and task priorization self-managing autonomous distributed systems


  • Security-issues in p2p-based online social networks
  • Privacy and deletion-enforcement in distributed data storages
  • Secure routing in p2p and wireless mesh networks
  • (Colluding) routing misbehavior detection and prevention

Focus 1: SkyNet.KOM - Monitoring and Management of Peer-to-Peer Systems

Short: P2P-based platforms need the manageablity and monitoring of the quality of service in order to make it commercially usable. SkyNet.KOM aims at solving this issues.

Long: Peer-to-peer systems are very popular in current time. In peer-to-peer systems every peer contributes to maintain the infrastructure, ressources are shared and consumed. Millions of users user applications like Skype or BitTorrent. However, there is more below the surface of p2p applications.

For future peer-to-peer applications, like e.g. for peer-to-peer based social online networks or decentralized Service-oriented Architectures, the quality of service is crucial. A peer-to-peer infrastructure needs to be reliable against peer failures and provide a controlable quality similar to server-based solutions. In order to have a QoS-aware peer-to-peer infrastructure, novel monitoring and management solutions have been developed at KOM.

We can now observe the key performance indicators of a large-scale peer-to-peer system in the wild. Our monitoring approachs SkyEye.KOM gives us around 100 metrics regarding the CPU consumption at the peers, the hop count, response times, bandwidth utilization, memory usage, uptime behavior and many more. This information can be used to detect flaws, trends and shortcomings in the setup and configuration of the system.

As a next step, the user or provider of the peer-to-peer system may define quality goals, that are then automatically reached by the peer-to-peer system. For this, the monitored peer-to-peer system status is automatically analyzed using machine learning algorithms to detect effective re-configuration approaches, that are then implemented automatically. Thus a fully self-observing, self-configuring peer-to-peer system is created, that reaches and holds predefined quality goals.

Focus 2: LifeSocial.KOM - the Peer-to-Peer based Social Online Network 

Short: The decentralization of online social networks platforms may lead to profitable business cases, advanced user interaction and much more fun for the participants.

Long: LifeSocial is a peer-to-peer based online social network, using the capacities of the peers to provide a multimedia-rich platform to meet and collaborate with friends. This work is motivated by the weak collaboration features in current web-based social online networks and the immense costs that they generate at the provider. LifeSocial.KOM, not only offers more features for totaly no costs for the provider, it is also secure: Leaving the users the right to choose who may see their data.

LifeSocial.KOM is based on a OSGi-based framework, which allows to dynamically add new plugins and thus functionality to the system. It is easy to use and offers great possibilities also for the graphical user interface. A video of the features and the graphical user interfase can be found here.

LifeSocial is secure, provides authenticated communication and access control. You as a user have the solely power about you data, privacy concerns are strictly considered.

Currently LifeSocial is extended to become part of the SkyNet Project "Towards a Sentient Distributed Network". This enables the LifeSocial network to be self aware and to decide without user interaction about steps to improve its existence. As a next step we perform an alpha test, preparing a public beta test in January. We are looking for interested design students creating a corporate identity for LifeSocial.KOM.


All publications of Kalman Graffi - until 2010


Kalman Graffi, Dominik Stingl, Julius Rückert, Aleksandra Kovacevic, Ralf Steinmetz:
Monitoring and Management of Structured Peer-to-Peer Systems  In: The 9th IEEE International Conference on Peer-to-Peer Computing (P2P'09), IEEE Computer Society Press, September 2009.


Parag Mogre, Kalman Graffi, Matthias Hollick, Ralf Steinmetz: “A Security Framework for Wireless Mesh Networks“, to appear in Wiley InterScience Wireless Communications and Mobile Computing (WCMC), Special Issue on "Architectures and Protocols for Wireless Mesh, Ad Hoc, and Sensor Networks", 2010.


Kalman Graffi, Patrick Mukherjee, Burkhard Menges, Daniel Hartung, Aleksandra Kovacevic, Ralf Steinmetz:
Practical Security in P2P-based Social Networks. In: IEEE International Conference on Local Computer Networks (IEEE LCN '09), IEEE Computer Society Press, October 2009


Kalman Graffi, Aleksandra Kovacevic, Song Xiao, Ralf Steinmetz:
SkyEye.KOM: An Information Management Over-Overlay for Getting the Oracle View on Structured P2P Systems. In: The 14th IEEE International Conference on Parallel and Distributed Systems (ICPADS'08), p. 279--286, IEEE Computer Society Press, December 2008.


Kalman Graffi, Sergey Podrajanski, Patrick Mukherjee, Aleksandra Kovacevic, Ralf Steinmetz:
A Distributed Platform for Multimedia Communities. In: IEEE International Symposium on Multimedia (ISM '08), p. 6, IEEE Computer Society Press, December 2008.


Kalman Graffi, Aleksandra Kovacevic, Nicolas Liebau, and Ralf Steinmetz:
From Cells to Organisms: Long-Term Guarantees on Service Provisioning in Peer-to-Peer Networks. In: ACM: 8th ACM SIGAPP International Conference on New Technologies of Distributed Systems (NOTERE '08), p. 6, ACM Press, June 2008.


Kalman Graffi, Sebastian Kaune, Konstantin Pussep, Aleksandra Kovacevic, Ralf Steinmetz:
Load Balancing for Multimedia Streaming in Heterogeneous Peer-to-Peer Systems. In: ACM Press: 18th International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV '08), p. 6, ACM SIGMM, May 2008.


Kalman Graffi, Aleksandra Kovacevic, Ralf Steinmetz:
Towards an Information and Efficiency Management Architecture for Peer-to-Peer Systems based on Structured Overlays. no. KOM-TR-2008-2, March 2008.


Kalman Graffi, Aleksandra Kovacevic, Kyra Wulffert, Ralf Steinmetz:
ECHoP2P: Emergency Call Handling over Peer-to-Peer Overlays . In: International Workshop on Peer-to-Peer Network Virtual Environments (P2P-NVE), p. 58-67, National Tsing Hua University, Hsinchu, Taiwan, December 2007. ISBN 978-1-4244-1890-9.


Kalman Graffi, Parag Mogre, Matthias Hollick, Ralf Steinmetz:
Detection of Colluding Misbehaving Nodes in Mobile Ad Hoc and Mesh Networks. In: IEEE Global Communications Conference: GLOBECOM '07, November 2007.


Kalman Graffi, Konstantin Pussep, Sebastian Kaune, Aleksandra Kovacevic, Nicolas Liebau, Ralf Steinmetz:
Overlay Bandwidth Management: Scheduling and Active Queue Management of Overlay Flows. In: IEEE Computer Society, USA: IEEE Local Computer Networks '07, p. 334-342, October 2007. ISBN 0-7695-3000-1.


Parag Mogre, Kalman Graffi, Matthias Hollick, Ralf Steinmetz:
AntSec, WatchAnt and AntRep:Innovative Security Mechanisms for Wireless Mesh Networks. In: IEEE Local Computer Networks: IEEE LCN '07, p. 539-547, IEEE, October 2007. ISBN 978-0-7695-3000-0.


Nicolas Liebau, Konstantin Pussep, Kalman Graffi, Sebastian Kaune, Eric Jahn, André Beyer, Ralf Steinmetz:
The Impact Of The P2P Paradigm. In: Proceedings of Americas Conference on Information Systems 2007, August 2007.


Kalman Graffi, Aleksandra Kovacevic, Patrick Mukherjee, Michael Benz, Christof Leng, Dirk Bradler, Julian Schroeder-Bernhardi, Nicolas Liebau:
Peer-to-Peer Forschung - Überblick und Herausforderungen. In: it - Information Technology (Methods and Applications of Informatics and Information Technology), vol. 46, no. 5, p. 272-279, July 2007. ISSN 1611-2776.  http://it-information-technology.de/.


Kalman Graffi, Konstantin Pussep, Nicolas Liebau, Ralf Steinmetz:
Taxonomy of Active Queue Management Strategies in Context of Peer-to-Peer Scenarios. no. KOM-TR-2007-01, January 2007.


Kalman Graffi, Nicolas Liebau, Ralf Steinmetz:
Taxonomy of Message Scheduling Strategies in Context of Peer-to-Peer Scenarios. no. KOM-TR-2007-02, January 2007.

Lecturing and Students

Lectures and Exercises at Technische Universität Darmstadt

WS06/07 - WS09/10 Lecture “Communication Networks II” - Lecture, exam and exercise organization, design and implementation, designated responsibility

SS09 Lecture “Quality of Service in Telecommunication Networks“ - Support in organization of exam

Seminars, Lab Exercises at Technische Universität Darmstadt

Seminar “Advanced Topics of Future Internet Research” (WS06/07, WS07/08, WS08/09):
Selected topics, supervised the students. Topics include modeling of peer-to-peer systems, QoS-awareness and monitoring in peer-to-peer systems.

Project seminar “Advanced Topics in Distributed Systems“ (SS07, SS08, SS09):
Selected topics, implementation and evalutation of p2p mechanisms in state-of-the-art P2P simulators.

Bachelor lab exercise “Advanced Topics in Distributed Systems“ (WS 08/09, WS 09/10):
Design and implementation of GUI elements for a p2p-based online social network.

Master lab exercise “Advanced Topics in Distributed Systems“ (WS 08/09, WS 09/10):
Engineering of collaboration and management tools for a p2p-based online social network.

Supervised Diploma and Master Theses

1. Mu Mu, KOM-D-285, 2006, “User-Centric End-to-End QoS for Next Generation Network Services“
2. Kyra Wulffert, KOM-D-294, 2007, “Emergency Call Handling in Peer-to-Peer and Next Generation Networks“
3. Inna Kotchourova, KOM-D-299, 2007, “Evaluation and Extension of Analytical Models for P2P Systems“
4. Song Xiao, KOM-D-306, 2008, „Management Architectures for Efficient Resource Allocation in Peer-to-Peer Systems“
5. Daniel Brückmann, KOM-D-312, 2008, „Implementation and Evaluation of Distributed and Cooperative Authentication Mechanisms for Decentralized Systems“
6. Sergey Podrajanski, KOM-D-316, 2008, „A Peer-to-Peer based Framework for Large-Scale Social Networking Platforms“
7. Burkhard Menges, KOM-D-317, 2008, „Design and Implementaion of a Security Framework for Peer-to-Peer based Online Community Architectures“
8. Thomas Wetter, KOM-D-331, 2009, „Technical and Economical Model for the Cooperation of Internet Service Providers and Peer-to-Peer Applications“
9. Dominik Stingl, KOM-D-334, 2008, „Development of a Self-Optimizing Life Cycle Framework for Structured Peer-to-Peer Systems“
10. Christian Groß, KOM-D-351, 2009, „Live-Monitoring of Large-Scale Peer-to-Peer Systems“
11. Moustafa Zohdi, KOM-D-355, 2009, „Adaptation of Management and Leadership Strategies in Peer-to-Peer Networks“
12. Vitaliy Rapp, KOM-D-358, 2010, „Monitoring Solutions for Structured and Unstructured Peer-to-Peer Overlays“
13. Luciana Alvite, KOM-D-367, 2010, „A Flexible Framework for P2P Systems“
14. Florian Gattung, KOM-D-370, 2010, „Benchmarking and Prototypical Implementation of a Social Knowledge Network“
15. Holger Becker, KOM-D-368, ongoing, „Machine Learning of the Interdependencies in Peer-to-Peer Systems“
16. Benedikt Lind, KOM-D-399, ongoing, „Beta-Test of a P2P-based Digital Social Network“

Supervised Bachelor Theses

17. Jun Chen, KOM-S-244, 2007, „Analysis and Evaluation of Mechanisms that Monitor the Resource Usage in Peer-to-Peer Systems“
18. Jiawei Du, KOM-S-245, 2007, „Analysis and Evaluation of Matching Algorithms for Efficient Resource Allocation in Peer- to-Peer Systems"
19. Andreas Straninger, KOM-S-252, „Evaluation of Mechanisms for a Self-Organizing Self-Conscious Intelligent Network“
20. Yevgen Fanshil, KOM-S-259, 2008, „Design and Implementation of a Monitoring Architecture for Peer-to-Peer based Systems (e.g. FreePastry)“
21. Rubén Fraile Blázquez, KOM-S-264, 2008, „Literature Survey on Information Management Architectures for Peer-to-Peer Systems“
22. Ling Wang, KOM-S-268, 2008, „Taxonomy on Context Information in Peer-to-Peer Systems and their Measurement Methodology“
23. Yue Sheng, KOM-S-269, 2008, „Implementation of Chord and the Key-Based Routing Interface in PeerfactSim.KOM“
24. Jonas Oppenländer, coadvised at Department for Business Startups, 2008, „Market Analysis and Marketing Concept for a P2P-based Social Online Community“
25. Luciana Alvite, KOM-S-279, 2008, „Design and Implementation of a Service Oriented, Dynamic and Modular P2P-based Multimedia Online Community Platform using OSGi “
26. Moritz Bornwasser, KOM-S-281, 2008, „Design and Implementation of an extendible User Interface for LifeSocial.KOM“
27. Julius Rückert, KOM-S-0295, 2009, „Details and Principles in Monitoring and Systematically Improving of Large-Scale Structured Peer-to-Peer Systems“
28. Carsten Snider, KOM-S-0296, 2009, „Mobility Aware Peer-to-Peer Networking“
29. Christoph Neumann, KOM-S-0303, 2009, „Survey and Prototypical Implementation of Semantical Networks using Peer-to-Peer Technology“
30. Michael Behrisch, KOM-S-0318, 2009, „Literaturey Survey on Autonomic Computing in Peer-to-Peer Systems“
31. Hoang Minh Nguyen, KOM-S-0319, 2009, „Longterm Service Level Agreements in unreliable Peer-to-Peer Systems“
32/33. Damian A. Czarny and Alexander Gebhardt , coadvised at Real Time Systems Lab, 2010, "Engineering of an automated Evaluation Platform for distributed Applications"
34. Yang Yang, KOM-S-0320, ongoing, „Testing-Methodologies of large-scale Peer-to-Peer Systems“
35. Johannes Beutel, KOM-S-0361, ongoing, „Systematic Improvement of the Monitoring Solution SkyEye.KOM“