International Journal of IT, Engineering and Applied Sciences Research (IJIEASR) ISSN: 2319-4413 Volume 2, No. 3, March 2013 i-Xplore International Research Journal Consortium www.irjcjournals.org 1 Multipath Routing Protocol for Congestion Control in Mobile Ad-hoc Network Nilima Walde, Assistant Professor, Department of Information Technology, Army Institute of Technology, Pune, India Dhananjay Singh, Student of 2 nd Year, IT Deptt., Army Institute of Technology, Pune,India ABSTRACT Congestion occurs in mobile ad hoc networks (MANETs) with limited resources. Congestion control is a key problem in mobile ad-hoc networks. In such networks, packet transmissions suffer from interference and fading, due to the shared wireless channel and dynamic topology. Mobile ad hoc networks are wireless networks without the support of any fixed network infrastructure, which are typically characterized by no centralized access, self- organizing, rapid development, dynamic topology, multiple hops and so on. Due to such characteristics, MANETs have much potential for many applications. To answer those challenges, many routing algorithms in MANETs were proposed, so here by we are trying to identify the best routing algorithm which will improve the congestion control mechanism. Keywords MANETs, Ad-hoc network, congestion control I. INTRODUCTION A wireless ad hoc network is usually defined as a set of wireless mobile nodes dynamically self-organizing a temporary network without any central administration or existing network infrastructure. Since the nodes in wireless ad hoc networks can serve as routers and hosts, they can forward packets for other nodes if they are on the route from source to the destination. To prepare for this promising future, besides other issues, routing is an important problem in need of a solution that not only works well with a small network, but also sustains efficiency and scalability as the network gets expanded and the application data gets transmitted in larger volume. Though essential, routing in MANETs is a nontrivial matter. MOBILE AD-HOC NETWORK An ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any stand-alone infrastructure or centralized administration. Mobile Ad-hoc networks are self-organizing and self- configuring multihop wireless networks where, the structure of the network changes dynamically. This is mainly due to the mobility of the nodes. Nodes in these networks utilize the same random access wireless channel, cooperating in a friendly manner to engaging themselves in multihop forwarding. The node in the network not only acts as hosts but also as routers that route data to/from other nodes in network. In mobile ad-hoc networks where there is no infrastructure support as is the case with wireless networks, and since a destination node might be out of range of a source node transmitting packets; a routing procedure is always needed to find a path so as to forward the packets appropriately between the source and the destination. Within a cell, a base station can reach all mobile nodes without routing via broadcast in common wireless networks. In the case of ad-hoc networks, each node must be able to forward data for other nodes. This creates additional problems along with the problems of dynamic topology which is unpredictable connectivity changes. When too many packets are present in a part of a subnet, the performance degrades; this situation is called as congestion. Congestion in a network may occur when the load on the network i.e the number of packets sent to the network is greater than the capacity of network. Congestion is a problem that occurs on shared networks when multiple users contend for access to the same resources (bandwidth, buffers, and queues). II. MINIMUM OVERHEAD MULTIPATH ROUTING PROTOCOLS Multipath routing protocols that have been proposed for discovering and using multiple paths with minimum routing overhead fall into this category. Multipath routing protocols inherently need to discover as many paths as possible. To discover as many path as possible, a multipath routing protocol uses an additional type of control messages other than route request, route reply and route error messages. Thus, a lot of control overhead messages are generated in the network to discover and to maintain these paths. That is why discovering multiple paths with low overhead is the main objective of the following multipath routing protocols. 2.1 SPLIT MULTIPATH ROUTING The main objective of SMR is to reduce the frequency of route discovery processes and thereby reduce the control overhead in the network. The protocol uses a per packet allocation scheme to distribute a load into multiple paths. When a destination node receives route request packets from different paths, it chooses multiple disjoint routes