Essay: Modifications to Existing Ad Hoc Networks

Essay: Modifications to Existing Ad Hoc Networks
12/04/2011 Comments Off on Essay: Modifications to Existing Ad Hoc Networks Academic Papers on Information Technology,Sample Academic Papers admin

Sample Essay

In order to overcome the vulnerabilities of ad hoc network and to overcome the shortcomings of existing trust models, new trust mechanisms have been developed. These trust models are implemented as augmentation or modification to existing ad hoc routing protocols, which are Dynamic Source Routing (DSR) and Ad-hoc On-Demand Distance Vector (AODV) routing.  The DSR protocol According to Pirzada, Dutta and McDonald is a reactive routing protocol which uses IP source routing. This means that all data packets that are sent with the help of DSR protocol include a list of node that the packet needs to go through in order to get to its destination. When a route needs to be discovered, a packet with a unique identification number is sent out by a node.

All nodes which receive this packet append their IP address in its list and forward the packet to other nodes. The packet continues to traverse the network until it reaches its destination or it Time-to-Live timer expires. When the destination node receives the packet, it creates a reply packet containing the list of nodes through which the previous packet has traversed. The source node when receives this packet updates its route information to that particular node (Pirzada, Datta & McDonald, 2006). In AODV, however, a node only performs routing when it is required to discover or update its route paths for other nodes. When a route request packet is sent out by a node, each of the other nodes which receive this packet checks its own routing table for an entry to the destination, if a route is found or the node is itself the destination a route reply packet is broadcasted back, which is then unicast by intermediate nodes to the request originating node (Li, Lyu & Liu, 2004).

One of the trusts models which are implemented by modification of DSR protocol is suggested by Pirzada, Datta, and McDonald. In this implementation, the DSR protocol is modified such that the trust is enforced on the network. The protocol is modified so that each node measures the trust on other nodes by checking on their performance on the network. This model also implements a DSR-base trust dispersal mechanism which makes use of ROUTE REPLY packets of DSP to spread the trust information among the nodes of the network. The authors suggest that this implementation is best used with pure ad hoc network in which pre or post establishment requirements cannot be imposed (Pirzada, Datta & McDonald, 2006).

Another implementation of trust mechanism using DSR protocol is Ariadne. Ariadne uses TESLA broadcast protocol in order to authenticate routing message. This protocol carefully modifies the DSR protocol messages to implementation and authentication mechanism which is used by the destination to verify the originator of the message during route discovery. The initiator can also verify each entry in the ROUTE REPLY message sent by the destination node. It further implements security mechanism to prevent unauthorized nodes from sending ROUTE ERROR messages and flooding the network (Hu, Perrig & Johnson, 2005). However, as mentioned by Zapata and Asokan, this protocol requires clock synchronization which is considered to be an unrealistic requirement for ad hoc networks (Zapata & Asokan, 2002).

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