FILE SHARING
Reduction of overhead is
essential in increasing the scalability and power efficiency of peer-to-peer (P2P)
file sharing systems for mobile ad hoc networks (MANET). Previously researchers
mainly focused on reducing overhead of query process, and paid little attention
to file transfer process. A cluster-based P2P file sharing protocol for MANET,
focusing on file transfer process. This protocol uses the concept of cluster to
reduce overhead and applies a three-way handshaking process to form a cluster.
Within a cluster, a request agent transmits requests on behalf of other nodes
in the cluster, and a provider provides data packets for the cluster at the
request of the request agent. By confining the request response process between
the request agent and the provider, protocol overhead can be effectively
decreased. Moreover, this protocol utilizes request suppression to effectively
reduce the number of requests.
The cluster-based P2P
file sharing protocol operates alternately in two stages, i.e., cluster
formation stage and data transmission stage. During cluster formation stage, a
cluster is formed through a three-way handshaking process. After a cluster is
formed, the protocol shifts to data transmission stage, during which the
provider of the cluster periodically sends data packets to the whole cluster at
the request of the request agent. This stage lasts until the provider has
provided all requested data blocks, or the cluster breaks up due to node
mobility.
To simplify the design of the protocol, we
assume that each node has the same wireless transmission range and will
cooperate with other nodes by responding their requests. We also assume that
the maximum transmission unit of wireless network is equal for all nodes. The
file to be shared is split into blocks of equal size, each of which can fit
into a single packet. Each block is assigned a block identifier, which ranges
from zero to n-1, where n stands for the number of blocks in the file.
It
utilizes the location and interest feature of peers to improve the efficiency
of file query. Peers
are clustered based on the location and sub clustered based on the interest and file replication in peers so that
content delivery can be done fast and overloading on a single peer can be
avoided. Current peer-to-peer (P2P) file sharing methods in
mobile ad hoc networks (MANETs) can be classified into three groups: flooding-based,
advertisement-based, and social contact-based.
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