Mobile Ad hoc Network (MANET) is a self-organized wireless network, consisting of nodes (mobile devices) responsible for its creation, operation and maintenance. The communication in the MANET is of multihop in nature due to absence of any fixed infrastructure. An attacker may intrude easily into MANET by posing as legitimate intermediate node and present various types of security attacks on data exchanges taking place between source and destination. In this paper we study the impact of presence of black hole node on MANET performance on the basis of reachability, hop count, neighbor node density and path optimality. We observe that as the percentage of black hole nodes increases, the MANET performance degrades significantly.

Communication in Mobile Ad Hoc Network (MANET) is accomplished using routing protocols. These protocols provide an efficient and reliable path for data sharing. In static environment where the nodes are stationary these protocols performs exceptionally well but in an environment having mobile nodes the performance of these protocols degrade drastically. To investigate this factor various researchers developed mobility models using simulation tools such as QUALNET, NS-2 etc. These models represent the erratic movement of nodes and give us an idea regarding their location, velocity and acceleration change over time. This paper is an effort to study the effect of mobility models such as Random Way Point, File and Group Mobility Models on the performance of routing protocols using QUALNET simulator. The results show that the choice of mobility models affect the performance of routing protocol significantly.

In order to facilitate communication in Mobile Ad hoc Network (MANET), routing protocols are developed. The performance of these protocols depends upon various factors such as: transmission range, number of nodes deployed and mobility of the nodes. Another factor which affects the performance of MANET routing protocols is the environment in which ad hoc network is deployed. The MANET environment may contain obstacles such as mountains lakes, buildings and river. These obstacles restrict nodes movement but may or may not obstruct the effective transmission range of nodes deployed. This paper is an effort to evaluate the performance of MANET routing protocols in presence of obstacles by designing a simulator in MATLAB-10. To make the situation more realistic obstacle of different shapes, size, number and type were introduced in the simulation region. We found significant impact of the same on the performance of routing protocols.