IJICIS, Vol.13, No. 2 APRIL 2013 79 International Journal of Intelligent Computing and Information Science MODIFIED DYNAMIC SOURCE ROUTING (DSR) PROTOCOL FOR MOBILE AD HOC NETWORKS (MANET) A. R. Khalifa R. A. Sadek M. A. Al-Shora Systems & Computers department, Faculty of Engineering. Al-Azhar University Cairo, Egypt Computer Engineering Department, Faculty of Engineering, Arab Academy for Science Technology and Maritime Transport, Cairo - Egypt khalifah2@hotmail.com rowayda_sadek@yahoo.com M_a_m_al_shora@yahoo.com Abstract: Routing in Mobile Ad Hoc Network (MANET) is complex due to the fact that the network graph is episodically connected, and nodes get only intermittently connected because of nodes mobility, terrain, weather, and jamming that change topology rapidly. In this paper propose a new Cross-Layer Design (CLD) to achieve a reliable data transmission in MANET. A key challenge is to create a mechanism that can provide good delivery performance and high quality of service in intermittent networks. The key components of our approach include a Cross-Layer Design (CLD) to improve information sharing between different protocol layers. In order to improve the end-to-end performance of MANET, we present a mechanism that allows the network layer to adjust its routing protocol dynamically, based on signal strength along the end- to-end routing path for each transmission link. However, there is study done over the DSR routing protocol to enhance its performance. In this study, another way of enhancement studies a comparison and performance evaluation of DSR and Modified DSR routing protocols, this is done using NS2 Simulator to identify the protocol enhancement for MANET’s. Keywords: MANET, Routing Protocols, DSR, Modified DSR 1. Introduction A Mobile Ad hoc Network (MANET) is a dynamic wireless network without fixed infrastructure. Nodes may move freely and arrange themselves randomly. The contacts between nodes in the network do not occur very frequently. As a result, the network graph is rarely connected and message delivery required a mechanism to deal with this environment [1]. Routing in MANET using the shortest-path metric is not a sufficient condition to construct high-quality paths, because minimum hop count routing often chooses routes that have significantly less capacity than the best paths that exist in the network [2]. Most of the existing MANET protocols optimize hop count as building a route selection. Examples of MANET routing protocols are Ad Hoc On Demand Distance Vector (AODV) [3], Dynamic Source Routing (DSR) [4], and Destination Sequenced Distance Vector (DSDV) [5]. However, the routes selected based on hop count alone may be of bad quality, since the routing protocols do not ignore weak quality links, which are typically used to connect to remote nodes. These links usually have poor signal strength, hence higher frame error rates and lower throughput [6], [7]. The wireless channel quality among mobile nodes is time varying due to fading, Doppler Effect and path loss. Known that the shortest-path metric does not take into account the physical channel variations of the wireless medium, it is desirable to choose the route with minimum cost based on some other metrics which are aware of the wireless nature of the underlying physical channel. In MANET, there are many other metrics to be considered: signal strength, Signal to Noise Ratio (SNR), Packet Loss, Maximum available bandwidth etc. These metrics should come from a cross-layer approach in order to make the routing layer aware of