New Abstraction

      Multipath routing, sometimes called traffic dispersion , has been one of the most important current directions in the area of routing. The current routing is based on the single path routing - between a source and a destination, the single minimum-cost path tends to be selected although different cost metrics may yield different paths. However, in a reasonably well-connected network, there may exist several paths between a source-destination pair. The concept of multipath routing is to give the source node a choice at any given time of multiple paths to a particular destination by taking advantage of the connectivity redundancy of the underlying network. The multiple paths may be used alternately, namely, traffic taking one path at a time, or they may be used concurrently, namely, traffic flowing through multiple paths simultaneously.

                                Multipath was first proposed by Maxemchuk to spread the traffic from a source in space rather than in time as a means for load balancing and fault handling in packet switching networks .The method was shown to equalize load and increase overall network utilization; with redundancy, it improves the delay and packet loss properties at the expense of sending more data through the network. Since then, the multipath routing technique has been applied to various types of networks, such as the communication networks, B-ISDN, ATM networks, etc., and for various network control and management purposes, such as aggregating the bandwidth, minimizing the delay, supporting the Quality of Service (QoS) routing, smoothing the burstiness of the traffic, alleviating the network congestion, and improving the fault tolerance,

1.2 NEW EXISTING SYSTEM

      Mobile ad hoc networks (MANETs) and wireless sensor networks (WSNs) have received tremendous attention in the past few years. A MANET is a collection of nodes that can move freely and communicate with each other using thewireless devices. For the nodes that are not within the direct communication range, other nodes in the network work collectively to relay packets for them. A MANET is characterized by its dynamic topological changes, limited communication bandwidth, and limited battery power of nodes. The network topology of a MANET can change frequently and dramatically. One reason is that nodes in a MANET are capable of moving collectively or randomly. When one node moves out of/in to the transmission range of another node, the link between the two becomes down/up. Another reason that causes the topological changes is the unstable wireless links, which might become up and down due to the signal fading (obstacles between the two end nodes), interference from other signals, or the changing of transmission power levels. Most of the mobile nodes are battery powered, when the nodes run out of the battery power, the node failure will also cause the topological changes. Although a close relative to MANETs, a WSN differs from an ad hoc network in many aspects . The number of nodes in a WSN is usually much larger than that in an ad hoc network. Sensor nodes are more resource constrained in terms of power, computational capabilities, and memory. Sensor nodes are typically randomly and densely deployed (e.g., by aerial scattering) within the target sensing area. The post-deployment topology is not predetermined. Although in many cases the nodes are static, the topology might change frequently because the sensor nodes and the wireless channels are prone to failure.

1.2 PROPOSED SYSTEM

  Multipath routing has been studied for various network control and management purposes in various types of networks. In this section, we outline some of the applications of multipath routing that improve the performance of an ad hoc network and a sensor network.