International Journal of Computer Science & Management Studies, Vol. 12, Issue 02, April 2012 Protocols in Mobile Ad-Hoc Network Sachin Minocha M. Tech Student, Vaish College of Engineering, Rohtak, Haryana (India) Abstract MANETs are autonomously self-organized networks without infrastructure support. In a mobile ad hoc network, nodes move arbitrarily; therefore the network may experience rapid and unpredictable topology changes. Because nodes in a MANET normally have limited transmission ranges, some nodes cannot communicate directly with each other. Hence, routing paths in mobile ad hoc networks potentially contain multiple hops, and every node in mobile ad hoc networks has the responsibility to act as a router. This paper is a survey of active research work on routing protocols for MANET. Keywords: MANET, AODV, DSR, GSR. 1. Introduction MANET is a collection of wireless mobile nodes that communicate with each other using multi-hop wireless links without any existing network infrastructure or centralized administration [1]. Each node in the network behaves as a router and forwards packets for other nodes. A mobile ad-hoc network (MANET) is a self-configuring network of mobile routers (and associated hosts) connected by wireless links [2]. Some of the main features of MANET are listed below [3]: a. MANET can be formed without any preexisting infrastructure. b. It follows dynamic topology where nodes may join and leave the network at any time and the multi-hop routing may keep changing as nodes join and depart from the network. c. It does have very limited physical security and thus increasing security is a major concern. d. Every node in the MANET can assist in routing of packets in the network. e. Limited Bandwidth & Limited Power is mainly classified into static and dynamic routing. Static routing refers to routing strategies set in the router, manually or statistically. Dynamic routing refers to routing strategies learned by an interior or exterior routing protocol [4]. 2. in MANET is the process of information exchange from one host to the other host in a network [5]. is the mechanism of forwarding packet towards its destination using most efficient path. Efficiency of the path is measured in various metrics like, Number of hops, traffic, security, etc. There are number of routing protocols currently available in ad hoc networks [6]. Table Driven routing protocols attempts to maintain consistent up to date routing information for each and every node in the network. These protocols required to maintain a consistent view. A very different approach from table driven routing scheme is source initiated routing. This type of routing creates routes only when needed by the source node. When a node needs a route to a destination, it initiates a route discovery process with in the network. 403
International Journal of Computer Science & Management Studies, Vol. 12, Issue 02, April 2012 3. Classification of Protocols in MANET similar to DSDV but it improves DSDV in the sense that it avoids flooding of routing messages. It can be classified into two broad categories as shown in Figure 1. Pro-active Protocol GSR HSR DSDV Types of Protocol in Manet Re-active Protocol AODV LAR TORA Hybrid Protocols Figure 1: Classification of Protocol in MANET [7] 3.1. Proactive Protocol [7] In proactive routing scheme every node continuously maintains complete routing information of the network. This is achieved by flooding network periodically with network status information to find out any possible change in network topology. Current routing protocol like Link State (LSR) protocol (open shortest path first) and the Distance Vector Protocol (Bellman-Ford algorithm) are not suitable to be used in mobile environment. Destination Sequenced Distance Vector routing protocol (DSDV) and Wireless routing protocols were proposed to eliminate counting to infinity and looping problems of the distributed Bellman-Ford Algorithm. 3.1.1. Global State (GSR) ZRP In GSR protocol [8], nodes exchange vectors of link states among their neighbors during routing information exchange. Based on the link state vectors, nodes maintain a global knowledge of the network topology and optimize their routing decisions locally. Functionally, this protocol is 404 3.1.2. Hierarchical State (HSR) HSR [8] combines dynamic, distributed multilevel hierarchical clustering technique with an efficient location management scheme. This protocol partitions the network into several clusters where each elected cluster head at the lower level in the hierarchy becomes member of the next higher level. The basic idea of HSR is that each cluster head summarizes its own cluster information and passes it to the neighboring cluster heads using gateways. After running the algorithm at any level, any node can flood the obtained information to its lower level nodes. The hierarchical structure used in this protocol is efficient enough to deliver data successfully to any part of the network. 3.1.3. Destinationn Sequenced Distance Vector (DSDV) Destination-Sequenced Distance-Vector protocol [9] is a proactive table driven algorithm based on classic Bellman-Forprotocols, all nodes learn the network topology routing. In proactive before a forward request comes in. In DSDV protocol each node maintains routing information for all known destinations. The routing information is updated periodically. Each node maintains a table, which contains information for all available destinations, the next node to reach the destination, number of hops to reach the destination and sequence number. The nodes periodically send this table to all neighbors to maintain the topology, which adds to the network overhead. Each entry in the routing table is marked with a sequence number assigned by the destination node. The sequence numbers enable the mobile nodes to distinguish stale routes from new ones, thereby avoiding the formation of routing loops. 3.2. Reactive Protocol [10] Every node in this routing protocol maintains information of only active paths to the destination nodes. A route search is needed for every new destination therefore the communication overhead is reduced at the expense of delay to search the route. Rapidly changing wireless network topology may
International Journal of Computer Science & Management Studies, Vol. 12, Issue 02, April 2012 break active route and cause subsequent route search [10]. It is divided into three types that are AODV, LAR, TORA which can be explained below. 3.2.1. AODV The AODV [11] routing protocol is an on demand routing protocol, which means that routes are established when they are required. This routing protocol is based on transmitting Route Reply (RREP) packets back to the source node and routing data packets to their destination. Used algorithm consists of two steps: route discovery and route maintenance. Route discovery process begins when one of the nodes wants to send packets. That node sends Route Request (RREQ) packets to its neighbors. Neighbors return RREP packets if they have a corresponding route to destination. However, if they don t have a corresponding route, they forward RREQ packets to their neighbors, except the origin node. Also, they use these packets to build reverse paths to the source node. This process occurs until a route has been found. Figure 2 : AODV Path Discovery Process [12] 3.2.2. Location-Aided (LAR) The goal of Location-Aided (LAR) [12] is to reduce the routing overhead by the use of location information. Position information will be used by LAR for restricting the flooding to a certain area [13]. In the LAR routing technique, route request and route reply packets similar to DSR and AODV are being proposed. The implementation in the simulator follows the LAR1 algorithm similar to DSR. Location Information: When using LAR, any node needs to know its physical location. This can be achieved by using the Global Positioning System (GPS). tables which only have information about the next hop and destination are used for routing information maintenance. When a route link disconnects, for example, a mobile node is out of range, neighbor nodes will notice the absence of this link. If so, neighbor nodes will check whether there is any route in their routing tables which uses a broken link. If it exists, all sources that send traffic over the broken link will be informed with Route Error (RRER) packet. A source node will generate a new RREQ packet, if there is still a need for packet transmission. When the route request broadcast reaches the destination or an intermediate node with a fresh enough route, the node responds by sending a unicast route reply packet (RREP) back to the node from which it received the RREQ [12]. So actually the packet is sent back reverse the path built during broadcast forwarding. A route is considered fresh enough, if the intermediate node s route to the destination node has a destination sequence number which is equal or greater than the one contained in the RREQ packet. As the RREP is sent back to the source, every intermediate node along this path adds a forward route entry to its routing table. Expected Zone: When a source node S wants to send a packet to some destination node D and needs to find a new route, it first tries to make a reasonable guess where D could be located. Suppose node S knows that at time D s position was P and that the current time is. Using this information S is able to determine the expected zone of D from the viewpoint of node S by time. For instance if D traveled with an average speed v, the source node S expects D to be in a circle around the old position P with a radius ( ). The expected zone is only an estimate by S to determine possible locations of D. If D traveled with a higher speed than S expected, the destination node may be outside the expected zone at time 405 Figure 3 : LAR Expected Zone [12]
International Journal of Computer Science & Management Studies, Vol. 12, Issue 02, April 2012 3.2.3. Temporally Ordered Algorithm (TORA) TORA [14] is a distributed highly adaptive routing protocol designed to operate in a dynamic multihop network. TORA has four basic functions: route discovery, route maintenance, route erasing and route optimization. TORA uses an arbitrary height parameter to determine the direction of link between any two nodes for a given destination. Consequently, multiple routes often exist for a given destination but none of them are necessarily the shortest route. To initiate a route, the node broadcasts a QUERY packet to its neighbors. This QUERY is rebroadcasted through the network until it reaches the destination or an intermediate node that has a route to the destination. The recipient of the QUERY packet then broadcasts the UPDATE packet which lists its height with respect to the destination. When this packet propagates in the network, each node that receives the UPDATE packet sets its height to a value greater than the height of the neighbor from which the UPDATE was received. This has the effect of creating a series of directed links from the original sender of the QUERY packet to the node that initially generated the UPDATE packet. When it was discovered by a node that the route to a destination is no longer valid, it will adjust its height so that it will be a local maximum with respect to its neighbors and then transmits an UPDATE packet. If the node has no neighbors of finite height with respect to the destination, then the node will attempt to discover a new route as described above. When a node detects a network partition, it will generate a CLEAR packet that results in reset of routing over the ad hoc network. 3.3. Hybrid Protocol Often reactive or proactive feature of a particular routing protocol might not be enough; instead a mixture might yield better solution. Hence, in the recent days, several hybrid protocols are also proposed. Example of Hybrid Protocol [8] is Zone Based Protocol (ZRP). 3.3.1. Zone Based Protocol (ZRP) In ZRP [10], each node proactively maintains the topological information within its routing zone (i.e., within a predefined distance) only. ZRP exploits the structure of the routing zone through a process known as bordercasting. Border casting allows a node to send messages to its peripheral nodes (nodes on the boundary of its routing zone) and prevents non 406 peripheral nodes from accessing the messages. Route discovery is efficiently done by bordercasting a route query to all the source s peripheral nodes, which in turn bordercast the query to their peripheral nodes and so on if the destination is not within their respective routing zones. Once the destination is found, a route reply is echoed back to the source. The ZRP path, which consists of a list of peripheral nodes between the source and the destination, is stored in the packet header or cached in the queried peripheral nodes. Any change in the peripheral nodes may render another route discovery. 4. Conclusion Mobile ad hoc networks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. In Mobile Ad hoc Network (MANET), interference reduces significantly the network performance such as data loss, conflict, and retransmission and so on. Therefore, interference is one of the important problems in research. This paper focuses on many protocols to find the route in MANET. But there are not many routing protocols about interference so in future we suggest to study routing protocols about interference. References [1] S. Shah, et al., Performance Evaluation of Ad Hoc Protocols Using NS2 Simulation, Proceedings of the National Conference on Mobile and Pervasive Computing (CoMPC- 2008), Chennai, India, August 2008. [2] Wikipedia, The free encyclopedia-, Mobile adhoc Network, http://en.wikipedia.org/wiki/mobile_adhoc_network, Oct-2004 [3] Charles E.Perkins and Elizabeth M. Royer, Ad hoc on demand distance vector (AODV) routing (Internet-Draft), Aug-1998. [4] K. Gorantala, Protocols in Mobile Ad Hoc Networks, Master Thesis, Department of Computing Science, Umeøa University, Sweden, June 2006. [5] Humayun Bakht, Computing Unplugged, Wireless infrastructure, Some Applications of Mobile ad hoc networks, http://www.computingunplugged.com/issues/ issue200410/00001395001.html, April-2003. [6] Beigh Bilal Maqbool et. al., Classification of Current Protocols for Ad Hoc Networks - A Review, International Journal of Computer
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