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to their neighbors. N0 will wait for their replies for a stipulated period of
time. While N0 waits, the other nodes forward their findings, and some of
these node runs would probably inform N0 of the location of file X. At the
end of the stipulated waiting period, each node that has sent out file requests
to its neighboring nodes would have received several replies. Therefore, the
temp table for each node has to be changed.
4.4 Simulation
4.4.1 assumptions
After the requesting node obtains responses from many assigned neighbors,
they are added to the neighbor list of the requesting node and each neighbor
is given a credibility number of 0.5, which would be the neighbor's initial
credibility. The neighbor list can be updated when the requesting node sends
out resource-related queries to the neighbors and when it later begins trans-
actions. One of the problems that could be faced is that for a given requesting
node, it is difficult to establish the number of reliable neighbors. Another
problem is regarding the search depth. When the requesting node does not
know the node where the resource is located, it would send out search que-
ries to its neighbors. The requesting node's neighbors will have a depth of 1.
Further, if the neighbors do not know the location of the resource and for-
ward the node's requests to their own neighbors, these indirect neighbors
will have a depth of 2. Therefore, the request can be forwarded to any depth
ranging from 3 to the length of the resource chain L.
It is desirable that there are only a reasonable number of neighbors at each
stage of the search so that each node can refer to its limited set of neighbors and
compile the required information without a considerable amount of computing
effort. Further, it is desirable that the length of the resource chain is not very
large as to affect the search efficiency. At the same time, it is also desired that
such a resource chain can span almost all the nodes in the P2P community.
The scale of the P2P community T_Scale can be obtained in the following
manner by considering the number of neighbors for each node
N
and the
length of a resource chain
L
.
N
N
L
−
1
1
++ +++…+ =
NN NN
N
−
=
T_Scale.
2
3
4
L
−
1
1
In the case where
N
is sufficiently large, the above equation can be approxi-
mated to the following equation
N
L
−2
= T_ Scale.
