Cooperative and Reliable Packet-Forwarding on Top of AODV

1. Cooperative and Reliable Packet-Forwarding on Top of AODV Bracha Hod March 2006

2. Outline • Background • Mobile ad hoc network • Ad-hoc On Demand Distance Vector • Trust and reputation • Problem statement • Solution • Misbehaving detection • Reputation system • Misbehavior reaction • Simulation results • Conclusions

3. Mobile Ad hoc Network • An autonomous, self-configuring system of mobile devices (laptops, smart phones, sensors, etc.) connected by wireless links • Each node operates as both an end-system and a router • MANET characteristics: • Mobility and dynamic topology • Bandwidth-constrained • Energy-constrained • Prone to security threats

4. Mobile Ad hoc Network

5. MANET Routing Protocols • Proactive/Table-driven • Periodically broadcast information across the network in a controlled flood • Waste bandwidth and power consumption • Reactive/On-demand • Initiate a route only when it is required • Delay when building new routes

6. Ad-hoc On-demand Distance Vector • RFC 3561 (2003) • One of the leading protocols for MANET • Uses sequence numbers to avoid loops • Quick adaptation to dynamic networks • Low processing and memory overhead • Scalable

7. AODV Route Discovery Route Request Reverse Route Route Reply A B C D G E F

8. AODV Route Maintenance Hello Message Route Error A B C D G E F

9. Trust and Reputation • Trust • A subjective expectation a node has about another node’s future behavior, based on the history of their encounters • Reputation • A perception that a node creates through past actions about its intentions and norms • Reputation System • A system in which the nodes who participate in it compute rating values and then advertise these values among the other nodes

10. Problem Statement • MANET is vulnerable to many attacks • Packet dropping is the most common attack • Motivation to misbehave • Selfish nodes are interested in saving their battery life • Malicious nodes aim to damage other nodes • Misbehavior patterns we handle • Black hole node advertises itself as part of a path and then drop the packets • Gray hole node adversary selectively drops some packets but not other

11. Solution • Misbehavior Detection • Watch the neighbors and record their behavior • Reputation System • Maintain direct rating according to the observations • Exchange rating among nodes • Incorporate direct and indirect rating • Use trust information • Misbehavior Reaction • Classify nodes • Select reliable paths • Punish misbehaving nodes

12. First-Hand Observations • Overhear neighbors • Direct mode – getting packets explicitly • Promiscuous mode • Examine the overheard packets • Update the positive and negative actions i k j h

13. Direct Rating • Calculation and management of the rating using the Beta distribution function • Direct rating of a node j by its neighbor i

14. Rating Exchange • Local model as a result of MANET constrains • Reputation distribution is performed continuously • Neighbors’ direct rating and a black list of misbehaving nodes are exchanged among 1-hop neighbors • Limited detection and punishment in large and mobile networks

15. Trust • Misbehaving nodes might spread false rating information • The trust estimates the reliability of the reports

16. Second-Hand Observations • Accept indirect rating DRk,j if the node is trusted or if it passes the deviation test • Estimate of the indirect positive and negative actions based on the indirect rating • Combine the direct and indirect rating to a total rating

17. Misbehavior Reaction • Nodes’ classification • Total rating value with total positive and negative actions • Two nodes with the same total rating, but with different history are classified differently • Path selection • Greedy selection of the next hop • Path maintenance for partial dropping • Punishment of misbehaving nodes • Second chance when the rating is faded

18. Simulation Model • Simulation in GloMoSim • Standard parameters of the channel and radio model • IEEE 802.11 as the medium access protocol • Nodes are places randomly in the area • Movement by random waypoint model • Speed range of 5-20 m/s • Pause time range of 0-500s • Data packets transmission at constant bit rate (CBR) on routes above 1-hop length

19. Throughput of Well-behaving Nodes 50 Nodes 100 Nodes 15 Sources, 15 Black-holes 20 Sources, 30 Black-holes

20. Punishment of Misbehaving Nodes Data Packets Transmitted Data Packets for by Misbehaving Nodes Misbehaving Nodes That were not Transmitted 50 Nodes, 15 Sources, 15 Black-holes

21. Partial Dropping (Gray holes) Data Packets Dropped Dropping percentage of 50% Different Dropping (32% of the total rating) Percentages 50 Nodes, 15 Sources, 15 Gray-holes

22. Robustness against Advanced Liars Data Packets Received False Positives 50 Nodes, 15 Sources, 10 Black-holes

23. Scalability over AODV Throughput Data Packets Dropped 500 Nodes, 250 static and the remainder walk on speed of 5-10 m/s. 30 Sources, 50 black holes

24. Conclusions • A reputation system on top of AODV is effective for both partial and complete dropping • The reputation system remained robust against advanced liars, when a majority of the nodes are trustworthy • In large and unstable networks, it is better to rely on self-observations because the network conditions have greater effect than the reputation system benefits

25. Thank you!