Publikationen
Konferenzbeiträge | Dissertationen | Technische Berichte
Konferenzbeiträge
N. I. Damm, Dietrich Fahrenholtz und Volker Turau. On Fluctuation Resilience of Second Generation Distributed Hash Tables. In Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in verteilten Systemen (KiVS'07), Februar 2007, pp. 105–110. Bern, Switzerland.
@InProceedings{Telematik_DFT_2007_FluctuationResilience,
author = {N. I. Damm and Dietrich Fahrenholtz and Volker Turau},
title = {On Fluctuation Resilience of Second Generation Distributed Hash Tables},
booktitle = {Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in verteilten Systemen (KiVS'07)},
pages = {105-110},
month = feb,
year = 2007,
location = {Bern, Switzerland},
}
Abstract:
Every Peer-to-Peer system destined for wide-spread use has to face the challenges imposed by peer population dynamics, which result from peers joining and leaving the system at their own discretion. So any Distributed Hash Table (DHT) design must take precautions against this peer population fluctuation (aka. churn) to sustain efficient lookup performance. Although important, an analysis of the influence of fluctuation on the performance of second generation DHTs in a unified attempt has not been done yet. An existing performance versus cost analysis by Li et al. aims at finding optimal parameters for DHTs being evaluated. However, their analysis focuses on one fluctuation scenario only. In this paper, we analyse second generation DHTs covering a wide range of topologies in a simulation framework under different fluctuation rates and evaluate their performance. Overall Kademlia attains the best lookup performance but its bandwidth consumption goes up significantly when increasing fluctuation rate. With a limited bandwidth budget and high fluctuation rate, Kelips lookup performance is the best among all examined DHTs.
Dietrich Fahrenholtz, Volker Turau und Andreas Wombacher. On Optimal Replication Group Splits in P2P Data Stores Based on the Hypercube. In Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'07), Februar 2007, pp. 155–162. Bern, Switzerland.
@InProceedings{Telematik_FTW_2007_ReplicationGroupHypercube,
author = {Dietrich Fahrenholtz and Volker Turau and Andreas Wombacher},
title = {On Optimal Replication Group Splits in P2P Data Stores Based on the Hypercube},
booktitle = {Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'07)},
pages = {155-162},
month = feb,
year = 2007,
location = {Bern, Switzerland},
}
Abstract:
P2P data stores excel if availability of inserted data items must be guaranteed. Their inherent mechanisms to counter peer population dynamics make them suitable for a wide range of application domains. This paper presents and analyzes the split maintenance operation of our P2P data store. The operation aims at reorganizing replication groups in case operation of them becomes suboptimal. To this end, we present a formal cost model that peers use to compute optimal points when to run performance optimizing maintenance. Finally, we present experimental results that validate our cost model by simulating various network conditions.
Dietrich Fahrenholtz und Volker Turau. Improving Churn Resistance of P2P Data Stores Based on the Hypercube. In Proceedings of the the 5th International Symposium on Parallel and Distributed Computing (ISPDC'06), Juli 2006, pp. 263–270. Timisoara, Romania.
@InProceedings{Telematik_FT_2006_ImprovingChurnResistance,
author = {Dietrich Fahrenholtz and Volker Turau},
title = {Improving Churn Resistance of P2P Data Stores Based on the Hypercube},
booktitle = {Proceedings of the the 5th International Symposium on Parallel and Distributed Computing (ISPDC'06)},
pages = {263-270},
day = {6-9},
month = jul,
year = 2006,
location = {Timisoara, Romania},
}
Abstract:
P2P data stores as opposed to pure P2P networks display their special strength if availability of inserted data items must be guaranteed. Their inherent mech- anisms to counter peer population fluctuation, where peers continuously join or leave the network, make P2P data stores suitable for a wide range of application do- mains. This paper examines one of their maintenance operations called fusion. It reorganizes parts of our P2P data store in case the peer population shrinks so much that data availability is threatened. We present a formal cost model that is used to estimate the optimal point when a fusion is to be invoked. Finally, the paper presents experimental results showing our cost model is valid by simulating various network conditions.
Dietrich Fahrenholtz und Andreas Wombacher. A Formal Communication Model for Lookup Operations in a Hypercube-based P2P Data Store. In Proceedings of the 1st International Conference on n Collaborative Computing: Networking, Applications and Worksharing, Dezember 2005. San Jose, USA.
@InProceedings{Telematik_FaWom_2005_LookUpHypercube,
author = {Dietrich Fahrenholtz and Andreas Wombacher},
title = {A Formal Communication Model for Lookup Operations in a Hypercube-based P2P Data Store},
booktitle = {Proceedings of the 1st International Conference on n Collaborative Computing: Networking, Applications and Worksharing},
day = {19-21},
month = dec,
year = 2005,
location = {San Jose, USA},
}
Abstract:
P2P data stores achieve high data availability by introducing replication of data. As a consequence, searching data may require to follow several routing paths introducing additional communication. A formal model of this additional communication is introduced and evaluated based on a hypercube based P2P data store.
Volker Turau, Dietrich Fahrenholtz und Marcus Venzke. Online Assessment for University Admission: Goals, Problems, and Experience. In Proceedings of the 9th International Computer Assisted Assessment Conference (CAA'05), Juni 2005, pp. 457–467. Loughborough, UK.
@InProceedings{Telematik_TFV_2005_OnlineAssessment,
author = {Volker Turau and Dietrich Fahrenholtz and Marcus Venzke},
title = {Online Assessment for University Admission: Goals, Problems, and Experience},
booktitle = {Proceedings of the 9th International Computer Assisted Assessment Conference (CAA'05)},
pages = {457-467},
day = {5-6},
month = jun,
year = 2005,
location = {Loughborough, UK},
}
Abstract:
This paper reports on the experience gained during the implementation and operation of an online assessment system for recruitment of engineering and computer science students. We identified problems that have to be solved to make online assessment a worthwhile building block of university admission. The presented work includes techniques for evaluating and monitoring online assessment processes.
Dietrich Fahrenholtz und Volker Turau. A Tree-based DHT Approach to Scalable Weakly Consistent Data Management. In Proceedings of the First International Workshop on P2P Data Management, Security and Trust (PDMST'04), IEEE Computer Society Press, August 2004, pp. 991–998. Zaragoza, Spain.
@InProceedings{Telematik_FT_2004_TreebasedDHT,
author = {Dietrich Fahrenholtz and Volker Turau},
title = {A Tree-based DHT Approach to Scalable Weakly Consistent Data Management},
booktitle = {Proceedings of the First International Workshop on P2P Data Management, Security and Trust (PDMST'04)},
pages = {991-998},
publisher = {IEEE Computer Society Press},
month = aug,
year = 2004,
location = {Zaragoza, Spain},
}
Dietrich Fahrenholtz und Winfried Lamersdorf. Transactional Security for a Distributed Reputation Management System. In Proceedings of the 3rd International Conference on Electronic Commerce and Web Technologies, September 2002. Aix-en-Provence, France.
@InProceedings{Telematik_FL_2002_SecurityReputation,
author = {Dietrich Fahrenholtz and Winfried Lamersdorf},
title = {Transactional Security for a Distributed Reputation Management System},
booktitle = {Proceedings of the 3rd International Conference on Electronic Commerce and Web Technologies},
day = {2-6},
month = sep,
year = 2002,
location = {Aix-en-Provence, France},
}
Dietrich Fahrenholtz und Andreas Bartelt. Towards a Sociological View of Trust in Computer Science. In Proceedings of the 8th Research Symposium on Emerging Electronic Markets, September 2001. Maastricht, Netherlands.
@InProceedings{Telematik_FB_2001_SociologicalView,
author = {Dietrich Fahrenholtz and Andreas Bartelt},
title = {Towards a Sociological View of Trust in Computer Science},
booktitle = {Proceedings of the 8th Research Symposium on Emerging Electronic Markets},
day = {16-18},
month = sep,
year = 2001,
location = {Maastricht, Netherlands},
}
Dissertationen
Dietrich Fahrenholtz. A Hypercube-based Peer-to-Peer Data Store Resilient against Peer Population Fluctuation. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2008.
@PhdThesis{Telematik_Fahrenholtz_2008_Diss,
author = {Dietrich Fahrenholtz},
title = {A Hypercube-based Peer-to-Peer Data Store Resilient against Peer Population Fluctuation},
publisher = {Cuvillier Verlag, G{\"o}ttingen, Germany},
school = {Hamburg University of Technology},
address = {Hamburg, Germany},
edition = {1st},
year = 2008,
isbn = {978-3-86727-498-2},
}
Technische Berichte
Dietrich Fahrenholtz. Addendum to 'Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation'. Technical Report Report No. TR-2006-07-01, URN: urn:nbn:de:gbv:830-opus-3116, Hamburg University of Technology, Hamburg, Germany, Juli 2006.
@TechReport{Telematik_FWT_2006_AddendumLookupHypercube,
author = {Dietrich Fahrenholtz},
title = {Addendum to 'Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation'},
number = {Report No. TR-2006-07-01, URN: urn:nbn:de:gbv:830-opus-3116},
institution = {Hamburg University of Technology},
address = {Hamburg, Germany},
month = jul,
year = 2006,
}
Abstract:
This is an addendum to our report "Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation". Here we explore two questions: First, what is the probability of a lookup to get lost and, second, what is the probability that it will be duplicated at least once. To this end, we approach the questions on a probability theoretical basis and derive equations for both probabilities, means and variances. Graphs elucidate the behavior of the model.
Dietrich Fahrenholtz, Andreas Wombacher und Volker Turau. Performance of Lookup Operations in a Hypercube-based P2P Data Store : Theoretical Model and Performance Evaluation. Technical Report Report No. TR-2005-12-01, URN: urn:nbn:de:gbv:830-opus-1057, Hamburg University of Technology, Hamburg, Germany, Dezember 2005.
@TechReport{Telematik_FWT_2005_LookupHypercube,
author = {Dietrich Fahrenholtz and Andreas Wombacher and Volker Turau},
title = {Performance of Lookup Operations in a Hypercube-based P2P Data Store : Theoretical Model and Performance Evaluation},
number = {Report No. TR-2005-12-01, URN: urn:nbn:de:gbv:830-opus-1057},
institution = {Hamburg University of Technology},
address = {Hamburg, Germany},
month = dec,
year = 2005,
}
Abstract:
One way for Peer-to-Peer data stores to achieve high data availability is to replicate their data. This is necessary to counter the effects of peer population dynamics also known as churn. A consequence of churn is that locating a data item may require a peer to resend search messages thus introducing additional communication. A formal model of this communication pertaining to data item lookups is introduced and evaluated using simulation in this paper. Results hold true for hypercube-based P2P data stores.
Dietrich Fahrenholtz und Volker Turau. Fluctuation in Peer-to-Peer Networks: Mitigating Its Effect on DHT Performance. Technical Report Report arXiv:cs/0406027, arXiv.org e-Print Archive, Cornell University, Juni 2004.
@TechReport{Telematik_FT_2004_P2PFluctuation,
author = {Dietrich Fahrenholtz and Volker Turau},
title = {Fluctuation in Peer-to-Peer Networks: Mitigating Its Effect on DHT Performance},
number = {Report arXiv:cs/0406027},
institution = {arXiv.org e-Print Archive},
address = {Cornell University},
month = jun,
year = 2004,
}
Abstract:
Due to the transient nature of peers, any Peer-to-Peer network is in peril to falling apart if peers do not receive routing table updates periodically. To this end, maintenance, which affects every peer, ensures connectedness and sustained data operation performance. However, a high rate of change in peer population usually incurs lots of network maintenance messages and can severely degrade overall performance. We discuss three methods how to tackle and mitigate the effect of peer fluctuation on a tree-based distributed hash table.