Abstract
We analyze in detail the content retrieval process in kad. kad implements content search (publish and retrieval) functions that use the Kademlia Distributed Hash Table for content routing. Node churn is quite common in peer-to-peer systems and results in information loss and stale routing table entries. To deal with node churn, kad issues parallel route requests and publishes multiple redundant copies of each piece of information. We identify the key design parameters in kad and present an analytical model to evaluate the impact of changes in the values of these parameters on the overall lookup latency and message overhead. Extensive measurements of the lookup performance using an instrumented client allow us to validate the model. The overall lookup latency is in most cases 5 s or larger. We elucidate the cause for such high lookup latencies and propose an improved scheme that significantly decreases the overall lookup latency without increasing the overhead.
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Notes
This is an unrealistic assumption that provide optimistic results; for our purpose, this coarse analysis is sufficient to understand the impact of the parameters.
We provide the modified files of the aMule client as well as the list of keywords we used at http://www.eurecom.fr/~btroup/kadlookup/.
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Acknowledgements
The authors would like to thank Antonio Trifilo and Emanuele Leomanni for their work on the aMule code.
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This work was done while M. Steiner and D. Carra were at Eurecom.
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Steiner, M., Carra, D. & Biersack, E.W. Evaluating and improving the content access in KAD. Peer-to-Peer Netw. Appl. 3, 115–128 (2010). https://doi.org/10.1007/s12083-009-0053-7
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DOI: https://doi.org/10.1007/s12083-009-0053-7