1. Environment-Aware Reputation Management for Ad Hoc Networks
Tamer Nadeem
Siemens Corporate Research

2. Significance of node cooperation
Key network functionalities such as medium access and routing depend on node cooperation.
Routing
Multi-hop communication.
Each node acts as a router as well as terminals.
Medium Access
Transmitting nodes seek exclusive access to the medium.
Node Misbehavior
Selfish
Malicious B A C
Routing is Cooperation-based D ! ! ! ! B
Medium Access is Cooperation-based A ! ! ! !

3. Problem Statement
Dynamic conditions (temporal and Spatial) perceived differently:
Channel condition
Traffic intensity,
Node available resources (e.g. battery power, bandwidth, etc.).
Topology dynamics (i.e., node mobility)
Identify node behavior and distinguish between a node’s willful decision not to cooperate (i.e. misbehavior) and its inability to do so due to adverse network environment.
This research investigates adaptation in reputation management systems.
Reputation management systems are meant to evaluate node behavior and identify node that behave inappropriately in an ad hoc network
Typically, the functionalities …. Meaning that different node carry out the different functionalities of reputation management in the same way across time and space.
However, node behavior is affected by local and network-wide conditions.

4. Challenges
Identify and accurately measure condition/resources that affect nodes’ willful decisions.
Assess and account for the impact of topology changes.
Increased awareness comes at the cost of increased complexity.
The more the nodes become aware of their surroundings, the more resources they have to consume in the process. This includes energy and computational resources. Mechanisms are needed to weigh in the need for awareness against the consumption of resources needed to be aware and to adapt node awareness temporally and spatially as needed and as can be tolerated.

5. EARMAHOC
Research towards realizing environment- awareness in reputation management system for ad hoc networks.
Aware of the temporal and spatial network environment factors that affects node behavior.
Reputation management systems are meant to evaluate node behavior and identify node that behave inappropriately in an ad hoc network
Typically, the functionalities …. Meaning that different node carry out the different functionalities of reputation management in the same way across time and space.
However, node behavior is affected by local and network-wide conditions.

6. Adaptive Slot Duration
Slot duration should adapt to network activity.
Misbehavior detection time using different evaluation slot durations.

7. Adaptive Slot Duration
We use routing activity as a measure of network activity:
Frequency of route establishment, route update, and route expiration events increases as network activity increases (otherwise network becomes unstable).
Comparing average time between consecutive routing operations to optimal average slot duration

8. Adaptive Slot Mobility Environment
Very short duration of activities irrespective of the traffic load  too few events.
Nodes evaluated within each slot may be different due to the changes in the topology.
Packet drops due to the instability of routes.

9. Adaptive Slot Mobility Environment
We allow historic records of behavior assessments and decisions to contribute to current decisions.
concept of virtual time-slotting
Virtual slot duration differs for each node under evaluation and depends on the observations made so far that reflect that node’s behavior.
virtual slotting may
spans beyond the boundaries of contiguous time slots

10. The End…

11. Use Cases
Enterprise Networks
Vehicular Networks
Social Networks

12. Reputation management systems mitigate against misbehavior
The functionalities of a reputation management system are:
Promote Cooperation: encourage nodes to cooperate.
Evaluation: evaluate nodes’ quality of behavior based on their cooperation.
Detection: distinguish nodes according to their behavior (cooperative vs. misbehaving nodes).
Reaction: appropriately react to misbehaving nodes.
Homogeneous application of the reputation management functionalities.
Reputation management systems mitigate against misbehavior

13. Overall objectives of this research
To investigate adaptation in reputation management systems.
To satisfy this goal, we:
Define a formal framework for reputation management systems:
Identify the components of a reputation management system and how these components interact.
Develop a model for detection of routes that include misbehaving nodes.
Develop an autonomous reputation management system
Assume node independence with respect to the reputation management system functionalities.
Study adaptation of the reputation management system functionalities.
Overall objectives of this research

14. Characteristics of an Adaptive Reputation Management System
Sensitive: able to capture changes in node behavior.
Adaptable: able to adjust according to the network conditions
Accurate: able to distinguish between cooperative and misbehaving nodes unambiguously.
Prompt: timely detects misbehaving nodes.
Characteristics of an Adaptive Reputation Management System

15. System Requirements
It must be aware of the network environment factors that may affect node behavior (e.g., congestion, contention, shadowing and path loss)
It must be aware of any shortage in resources that may affect other nodes’ willful decisions to forward packets.
third category of nodes can be created (where the first and second cooperative and misbehaving nodes) distinguishes such nodes as disadvantaged.
It must be aware of the topology dynamics and their impact on packet forwarding.
Reputation management systems are meant to evaluate node behavior and identify node that behave inappropriately in an ad hoc network
Typically, the functionalities …. Meaning that different node carry out the different functionalities of reputation management in the same way across time and space.
However, node behavior is affected by local and network-wide conditions.