SIL Model

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					Fast Searching in Peer-to-Peer
          Networks
  Self-Organizing Parallel Search Clusters

              Rocky Dunlap
                   Agenda
•   Peer-to-peer Networks
•   Search Links/Index Links Model
•   Parallel Search Clusters
•   Self-Organizing Parallel Search Clusters
•   Further Research
        Peer-to-Peer Networks
•   Peer = Client + Server
•   Anyone can send/process messages
•   Highly Distributed
•   Highly Parallel
•   Data-centric routing
    P2P Networks – Two Types
• Unstructured             • Structured
• “Loose” network          • Specific network
  structure                  structure
• Requires less control    • Distributed Hash Tables
                              – Smart routing
  of peers (casual
  searching)               • Guarantees:
                              – Bounded hops
• Fault tolerance, churn      – Bounded state
• Keyword searching           – Ability to search entire
                                network
Unstructured Searching




         ?
             The Problems
• Query saturation – every node processes
  every query
• Query processing redundancy
• Slow response time from distant nodes
• In reality, cannot search entire network
  (TTL)
• Need a model for studying P2P networks
                SIL Model
• Search Links (forwarding)




• Index Links (non-forwarding)
    SIL Model


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              Parallel Search Clusters




                                    Searches remain
                                    inside cluster
Index links provide
full coverage
        Parallel Search Clusters
• Assumptions
   – Keep network essentially unstructured (keyword
     searching, fault tolerance)
   – Search rate is high
   – Update rate is low
• Limit the number of nodes that processes query
• Provide full (or high) coverage of network
• Index links allow some nodes to proxy searches
  for others
              The Challenge
• Self-Organizing Parallel
  Search Clusters
• Decentralized
• Nodes only know a few
  neighbors
• Dealing with “churn”
• Minimal interruption of
  normal operations
             Proposed Solution
• Existing clusters split into two new clusters
• Advantages
   – Solves origin problem (start with one cluster)
   – Clusters split autonomously
   – Automatic load balancing
• Three phase approach
   – Color
   – Replicate Links
   – Split
Splitting Cluster




       !

                    Phase 1
                    Coloring
Splitting Cluster




          !

                     Phase 1
Color (radius = 2)   Coloring
Splitting Cluster




                     Phase 1
Color (radius = 2)   Coloring
         Splitting Cluster

green




        green
                                  red

                      red




                red

                            red

                                          Phase 2
                                        Replicate Links
              Splitting Cluster

      red




              red




red




        red
                                    Phase 2
                                  Replicate Links
Splitting Cluster




        X
                    Phase 3
                     Split
Splitting Cluster


            X



                    Phase 3
                     Split
Splitting Cluster




                    Phase 3
                     Split
        Splitting Cluster

                     X
    X
          X    X
X

X        X    X
                            Phase 3
                             Split
Splitting Cluster




                    Phase 3
                     Split
Splitting Cluster




                    Phase 3
                     Split
              Further Research
• Initiating the split
• Choosing the radius for coloring phase
   – Want two clusters of same size
• Overloading index links
• Dealing with “churn”
   – Nice nodes
   – Not-so-nice nodes
• Merge operation?
• Simulation
              Bibliography
• B. F. Cooper and H. Garcia-Molina. SIL:
  Modeling and Measuring Scalable Peer-to-peer
  Search Networks. http://www-
  db.stanford.edu/~cooperb/pubs/searchnets.pdf,
  2003.
• B. Yang and H. Garcia-Molina. Improving Search
  in Peer-to-Peer Networks.
  http://dbpubs.stanford.edu:8090/pub/2002-28,
  2002.

				
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posted:11/16/2011
language:English
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