TCP optimization in mobile ad hoc networks is a in performance in the form of poor throughput and very high challenging issue because of some unique characteristics of interactive delays. Therefore, route changes due to host MANETs. Some of the main reasons behind TCP's performance mobility can have a detrimental impact on TCP performance. degradation in these networks are lossy channels, frequent route Most of the proposed solutions to this problem on TCP deals failures, network partitions.with freezing congestion window size and retransmissionIn this paper, a cross-layer TCP protocol with adaptive modulation for MANET is proposed. Medium access (MAC) layer timeout period whenever a node receives an error message or a is responsible to decide the modulation scheme to be used at the link failure notification messages and restores them when link physical layer depending on the signal strength and queue length resumes. Certainly there is no guarantee that the route of the receiver. An ns2.30-based simulation analysis of the reestablished is same as the earlier route, in such case proposed protocol which provides better TCP performance with parameter restoration will not provide a better performance in a minimum congestion than the existing TCP protocols is described. MANETs. One of the solutions to this problem is by increasing The effects of mobility of nodes, no. of connections on TCP the data rate by using different modulation schemes between parameters such as throughput, packet delivery ratio and round nodes at the physical layer which provides better TCP trip time are investigated.performance. Since, the routes are temporary in these networks Keywords: TCP, adaptive modulation, data rate, queue length, so we try to forward the data as much as possible before the congestion, route failure. link fails.

Mobile ad-hoc networks (MANETs) are composed of mobile nodes connected by wireless links without using any pre-existent infrastructure. Hence the assigning of unique IP address to the incoming node becomes difficult. There are various dynamic auto configuration protocols available to assign IP address to the incoming nodes including grid based protocol which assigns IP address with less delay and low protocol overhead. Such protocols get affected by presence of either selfish nodes or malicious nodes. Moreover there is no centralized approach to defend against these threats like in wired network such as firewall, intrusion detection system, proxy etc. The selfish nodes are the nodes which receive packet destined to it and drop packet destined to other nodes in order to save its energy and resources. This behavior of nodes affects normal functioning of auto configuration protocol. Many algorithms are available to isolate selfish nodes but they do not deal with presence of false alarm and protocol overhead. And also there are certain algorithms which use complex formulae and tedious mathematical calculations. The proposed algorithm in this paper helps to overcome the attack of selfish nodes effect in an efficient and scalable address auto configuration protocol that automatically configures a network by assigning unique IP addresses to all nodes with a very low protocol overhead, minimal address acquisition delay and computational overhead.