| 1. |
- Shafaat, Tallat M., et al.
(författare)
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A Practical Approach to Network Size Estimation for Structured Overlays
- 2008
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Ingår i: SELF-ORGANIZING SYSTEMS, PROCEEDINGS. - Berlin : SPRINGER-VERLAG. - 9783540921561 ; , s. 71-83
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Konferensbidrag (refereegranskat)abstract
- Structured overlay networks have recently received much attention due to their self-* properties under dynamic and decentralized settings. The number of nodes in all overlay fluctuates all the time due to churn. Since knowledge of the size of the. overlay is a core requirement for many systems, estimating the size in a decentralized manner is a challenge taken up by recent research activities. Gossip-based Aggregation has been shown to give accurate estimates for the network size, but previous work done is highly sensitive to node failures. In this paper, we present a gossip-based aggregation-style network size estimation algorithm. We discuss shortcomings of existing aggregation-based size estimation algorithms, and give a solution that is highly robust to node failures and is adaptive to network delays. We examine our solution in various scenarios to demonstrate. its effectiveness.
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| 2. |
- Shafaat, Tallat M., et al.
(författare)
-
Key-based consistency and availability in structured Overlay Networks
- 2008
-
Ingår i: Proceedings of the 17th International Symposium on High Performance Distributed Computing 2008, HPDC'08. - New York, NY, USA : ACM. - 9781595939975 ; , s. 235-236
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Konferensbidrag (refereegranskat)abstract
- Structured Overlay Networks (SONs) provide a promising platform for high performance applications since they are scalable, fault-tolerant and self-managing. SONs provide lookup services that map keys to nodes that can be used as processing or storage resources. In SONs, lookups for a key may return inconsistent results. Consequently, it is difficult to provide consistent data services on top of SONs that build on key-based search. In this paper, we study the frequency of occurrence of inconsistent lookups. We show that the affect of lookup inconsistencies can be reduced by using node responsibilities. We present our results as a trade-off between consistency and availability of keys.
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| 3. |
- Shafaat, Tallat M., et al.
(författare)
-
On consistency of data in structured overlay networks
- 2008
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Ingår i: GRID COMPUTING. - NEW YORK : SPRINGER. - 9780387094564 ; , s. 249-260
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Konferensbidrag (refereegranskat)abstract
- Data consistency can be violated in Distributed Hash Tables (DHTs) due to inconsistent lookups. In this paper, we identify the events leading to inconsistent lookups and inconsistent responsibilities for a key. We find the inaccuracy of failure detectors as the main reason for inconsistencies. By simulations with inaccurate failure detectors, we study the probability of reaching a system configuration which may lead to inconsistent data. We analyze majority-based algorithms for operations on replicated data. To ensure that concurrent operations do not violate consistency, they have to use non-disjoint sets of replicas. We analytically derive the probability of concurrent operations including disjoint replica sets. By combining the simulation and analytical results, we show that the probability for a violation of data consistency is negligibly low for majority-based algorithms in DHTs.
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