123 Chapter 8 Conclusions As a consequence to the previous chapters, a conclusion is finally presented here, summarising the findings, contributions and scope of future research in this field. 8.1. Summary of Works An important network system, as it is, Mobile Ad-Hoc Networks are deployable anywhere, anytime and is very flexible as well as cost-effective. However, in the context of vast potential of MANETs, they are not devoid of security issues. This thesis takes into account, and thereby analyses and proposes solutions to, these issues. Chapter 2 surveys and analyses MANET vulnerabilities. Inherently, ad-hoc networks are very prone to security threats. To meet all requirements and requisite conditions, these networks need to be highly secure and robust. There is still scope for improvement in bandwidth capacity, propagation, spectral reuse and certain energy issues. Ad-hoc networks are small in size, considerably cheap and have the inherent ability to be deployed even in dense forms such as the battlefield, etc. This chapter concludes that ad-hoc networks have a great future and research in this field will continue to be very active and imaginative. Chapter 3 carries out a detailed NS-2 based comparative simulation study of the performance characteristics of AODV, DSDV and DSR, with an attempt to compare these protocols in hybrid networking environment. The results indicate superiority in the performance of the two On-demand protocols namely DSR and AODV against the Tabledriven protocol, namely DSDV. It is also observed that DSR outperforms AODV in less stressful situations, whereas AODV outperforms DSR in more stressful situations. The routing overhead is consistently low for DSR and AODV than in comparison with DSDV especially for large number of nodes. It also shows that for real time traffic AODV is 124 preferred over DSR and DSDV. For less number of nodes and less mobility, DSDV’s performance is superior. Chapter 4 includes the routing security issues of MANETs, black hole attacks that can be mounted against a MANET and a proposed solution feasible for it in the AODV protocol. This solution may be applied for identifying single and multiple black hole nodes cooperating with each other in a MANET; and for discovering secure paths from source to destination by avoiding multiple black hole nodes acting in cooperation. The results show that the presence of a single black hole considerably increases packet loss (by 88.3% on average) and with two black hole nodes (by 98.2%) in the network. This loss is partially (49.86% and 66.52%) due to packets dropped in the black hole node and partially due to congestion in the network over the paths towards the black hole node. The proposed modified AODV protocol reduced the packet loss by 7.66% in presence of a single black hole node and by 17.57 % in case of two black hole nodes. The results also point at a reduction in Packet Delivery Ratio and Throughput. The detection of black holes in an adhoc network is challenging, and their attacks can cause serious damage. Keeping this in mind, the modified AODV routing protocol has been used for detecting and minimising the effects of a black hole attack. Chapter 5 deals with flooding attacks on MANETs and makes a venture to simulate and study the same. MANETs, being very important, efficient security models are needed to counter security attacks. With this in mind, a new trust establishment scheme (with trust function in DSR protocol) has been used for detection and prevention of flooding attacks. Though whole-hearted steps have been taken to minimize flooding attacks and their effects, there is still scope for further development so as to provide with a trustworthy security framework against flooding attacks on MANETs. Chapter 6 deals with Wormhole nodes and misbehaving nodes and finds ways to detect and prevent them. This chapter makes use of dynamic source routing protocol (DSR), modified in order to show the impact of the misbehaving nodes in the network. From the simulations results, the detection of wormhole nodes or malicious nodes by the proposed DSR i.e. WDSR is shown. These results also show that the mechanism correctly identifies such nodes and simply drops the routes containing the same. 125 Chapter 7 discusses the issue of different attacks and their effect(s) on the DSR-based routing protocol. In contrast to former investigations of single attack possibilities, the present analysis gives a detailed overview of each attack and allows the reader to directly compare and evaluate possible risks using defined criteria. Damage resulting from a successful attack is analysed, alongwith necessary effort, probability and skill levels completing a full picture of each attack, thus allowing comparison between the attacks. This systematic approach proves that the greatest damage results from a successful wormhole attack or black-hole attack, which also requires the greatest effort. On the other hand, flooding attacks have an average success probability but cause relatively low levels of damage though they are easy to perform. 8.2. Summary of Contribution In this thesis the main contribution is to find the problems and prospects of Mobile Ad Hoc Network. In this context, different MANET routing protocols are studied under various attacks along with their behaviour and their performance are analysed as well. After a detailed study, the proactive and reactive routing protocols (DSDV, AODV and DSR) were simulated to show which routing protocol is more prone to the attack due to their own characteristics. Then the black hole attacks is analysed which is one of the most severe attack on this wireless network and a modified protocol “Modified AODV” is proposed which is resistive to this type of attack and can detect and prevent the black hole attack to a greater extent. A new trust establishment scheme is used to detect and prevent another attack on similar environment i.e. flooding attack. A modified DSR protocol is proposed in which the trust estimation function is used and the performance of the network under the flooding attack is measured. Again a new modified routing protocol WDSR is developed which is based on traditional DSR for detection and prevention of wormhole attack. A comparative analysis of wormhole attack for both protocols (DSR and WDSR) is taken into account and is demonstrated with the help of performance metrics based on which the effectiveness of the proposed algorithm is shown. Finally in this thesis the performance comparison of these three attacks are shown under proposed and existing model in terms of cost, probability, skills and damage resulting from a successful attack. It is to be noted that the security threats that an ad hoc network faces are analysed and methods are shown to model these attacks in Network Simulator-2. 126 8.3. Future Research In future, several security solutions that have been proposed to secure routing protocols will be investigated and classified based on this classification. The investigation will include various techniques that might be employed in protecting, detecting, and responding to the attacks against the routing messages. There are plans to enhance our framework by automatically extracting useful features for detection of unknown attacks. It may be planned to design an intrusion detection system across multiple network layers to detect more sophisticated attacks. Also there may be comparisons in the performance of routing protocols with different types of selfish nodes in a bigger area with longer simulation time with different node pause time. Studies may also be conducted on the robustness of proactive and reactive routing protocol like OLSR, TBPF, ARIADNE etc. and find a way of detecting misbehaving nodes in MANETs.