The current peer-to-peer (P2P) content
distribution systems are constricted by their simple on-demand content
discovery mechanism. The utility of these systems can be greatly enhanced by
incorporating two capabilities, namely a mechanism through which peers can
register their long term interests with the network so that they can be
continuously notified of new data items, and a means for the peers to advertise
their contents. Although researchers have proposed a few unstructured
overlay-based publish-subscribe systems that provide the above capabilities,
most of these systems require intricate indexing and routing schemes, which not
only make them highly complex but also render the overlay network less flexible
toward transient peers. This paper argues that for many P2P applications,
implementing full-fledged publish-subscribe systems is an overkill. For these
applications, we study the alternate continuous query paradigm, which is a
best-effort service providing the above two capabilities. We present a scalable
and effective middleware, called CoQUOS, for supporting continuous queries in
unstructured overlay networks. Besides being independent of the overlay
topology, CoQUOS preserves the simplicity and flexibility of the unstructured
P2P network. Our design of the CoQUOS system is characterized by two novel
techniques, namely cluster-resilient random walk algorithm for propagating the
queries to various regions of the network and dynamic probability-based query
registration scheme to ensure that the registrations are well distributed in
the overlay. Further, we also develop effective and efficient schemes for
providing resilience to the churn of the P2P network and for ensuring a fair
distribution of the notification load among the peers. This paper studies the
properties of our algorithms through theoretical analysis. We also report
series of experiments evaluating the effectiveness and the costs of the
proposed schemes.
Keywords:
- Knowledge and Data Engineering Title, Data Mining
Title, Cloud Computing Title, Networking Title, wireless Compunctions Title.
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