Autor: | O. Waldhorst, C. Lindemann | Links: | DownloadBibtex |
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Quelle: | Proc. 3rd Int. ACM Workshop on Data Engineering for Wireless and Mobile Access (MobiDE), pp. 61-68, San Diego, California, USA, September 2003 | ||
This paper presents a general-purpose distributed lookup
service, denoted Passive Distributed Indexing (PDI). PDI
stores entries in form of (key, value) pairs in index caches
located in each mobile device. Index caches are filled by
epidemic dissemination of popular index entries. By exploiting
node mobility, PDI can resolve most queries locally without
sending messages outside the radio coverage of the inquiring
node. Thus, PDI reduces network traffic for the resolution of
keys to values. For keeping index caches coherent,
configurable value timeouts implementing implicit
invalidation and lazy invalidation caches implementing
explicit invalidation are introduced. Inconsistency in index
caches due to weak connectivity or node failure is handled by
value timeouts. Lazy invalidation caches reduce the fraction of
stale index entries due to modified data at the origin node.
Similar to index caches, invalidation caches are filled by
epidemic distributions of invalidation messages. Simulation
results show that with the suitable integration of both
invalidation mechanisms, more than 95% of results delivered
by PDI index caches are up-to-date for the considered
scenario.