W. Hoschek (Switzerland)
Peer-to-Peer Network, Virtual Hosting, Query Processing
In a Peer-to-Peer (P2P) network, a link topology such as a ring, tree or graph describes the link structure among autonomous nodes. A node deployment model defines where and how one or more partitions of the link topol ogy are physically running, stored and accessed. Link topology and node deployment are distinct and orthogo nal concepts, and hence a node deployment model need not correspond to a link topology at all. The sim plest (and most common) deployment model has distinct nodes running on distinct hosts. In this paper, we propose that nodes can also be concentrated in node containers, which are transparent software hosting environments that embed one or more virtual nodes. Node deployment models range from cen tralized to fully distributed. Virtual hosting has the po tential for increased query performance (as opposed to increased scalability). Thus, we introduce the separate P2P query scope parameters logical radius and physical radius, as well as three novel query execution strategies that transparently exploit the properties of virtual host ing. The key idea is to reduce or eliminate the need for messaging between container-internal nodes and to run as few as possible queries against the database of shared nodes. Under normal query execution and under collecting traversal, a query to a container node can be efficiently answered without violating the semantics of query and scope. Under the quick scope violating query strategy, a query can be answered even more efficiently, by relaxing the conditions imposed by the query scope.
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