A Persistent Structured Hierarchical Overlay Network to Counter Intentional Churn Attack

Algorithm 5

Key lookup operation in proposed architecture.

Key_Lookup

  // lookup algorithm for key issued by node

  () If is a super node of tree , then

  () If ( can answer query) then

// if issued query lies in local tree

  () Node = .Search_Tree()

  () Else // if cannot answer the query

  ()  = .Find_Tree()

  // query is routed in the top layer overlay to find the super node responsible for the key

  () Node = .Search_Tree()

  // find the node responsible for the storage of key in tree

  () Else

  // is not a super node

  () If ( can answer query) then

// if issued query lies in local sub tree range

  () 

  () Node = .Search_Tree()

  () Else // if query is not in local subtree

  () .Forward _Request(, root)

  // node will forward the key lookup request to its root

  () Go to step ().

  () Return 

.Find_Tree

  // node will find the super node responsible for node

  ()  = (, successor)

  () if ()

  // super node responsible for the key is found

  () return

  () else

  // forward the query to next node of the ring

  () .Find_Tree () 

.Forward_Request , Root

// Forward the request from node to the root of the tree

  () If ( is not a root node), then

  ()  = parent()

  () .Forward_Request(, Root)

  () else

  () Root =

Return