Enforce Collaboration in Mobile Ad Hoc Network
Ning JiangSchool of EECS
University of Central [email protected]
Outline
Mobile Ad Hoc Network Existing Techniques DSG Approach Conclusion
Mobile Ad Hoc Network A collection of devices equipped with
wireless communications and networking capability
Devices heterogeneity Palm, laptop, mobile phone, etc.
Infrastructureless Self-organizing and adaptive Nodes relay data packets for each other
Energy critical
Mobile Ad Hoc Network
Mobile Ad Hoc Network Applications
In the office Traveling Wireless home network Location/context based services Battlefield
Collaboration in Mobile Ad Hoc Network
Routing Dynamic Source
Routing Routing Request Routing Reply
Packet forwarding
Detecting Selfish Nodes Marti et al. ACM MOBICOM,
2001 Watchdog
Each node in promiscuous mode Each node verifies whether its
downstream node forwards packets
Packet loss threshold Inform the source node of the
misbehaving node Path Rater
Nodes select paths without selfish nodes
Drawbacks of the Approach No punishment to selfish nodes Each packet should be monitored Slow propagation of warning
information Selfish nodes have no chance to
rejoin
Packet Purse Model Hubaux et al. IEEE/ACM Workshop on
Mobile Ad Hoc Networking and Computing Reward the packet forwarding service
The originator loads each packet with a number of “nuggets”
Each forwarding node acquires one or more nuggets
Packets with insufficient nuggets are discarded Selfish nodes are detected and fined Relies on a temper resistant security module Cryptographic techniques are applied to
prevent abuse
Packet Purse Model Advantages
Secure Nodes are motivated to collaborate Selfish nodes are punished Node enjoin enabled
Disadvantages Still monitor each packet Generally, nodes have no knowledge of
selfish nodes Cryptographic overhead
CONFIDANT Protocol Birds and Mobile Ad Hoc Network
Sucker birds Cheating birds Grudger birds Interesting observation: starting with
a majority of cheating birds, grudger birds finally win over
Can Mobile Ad Hoc nodes also act like grudger birds? – Yes!!
CONFIDANT Protocol Sonja et al. MOBIHOC 2002 Monitor
Neighbor watch Reputation System
Evaluates selfish behaviors
CONFIDANT Protocol Trust Manager
Sends alarms to “friend” nodes A friend list
Checks the trustiness of incoming alarms
Several levels of trustiness Maintains a trust table of nodes
Path Manager Path ranking and management
CONFIDANT Protocol Drawbacks
Only informs friends about the malicious nodes
Control overhead Need to manage complex trust
relationships Rejoin not addressed
DSG Approach Main idea
Let the cheating bird inform others! Assumptions
Omni-directional antenna Security Module (smart card) There are TCP traffics
DSG Approach Finite State Model
Normal Detecting Penalized Rejoin
States stored in the security module
DSG Approach – Detecting Mechanism
Initially all nodes in Normal state Source monitors its TCP traffic No acknowledgement -> Detecting immediate
downstream node Two possibilities:
Neighboring node forwards packets -> detecting propagate
Neighboring node discards packets -> Marked as penalized, does not forward source node!
DSG Approach – Selfish Node Avoidance Selfish nodes are recognized and their
states switched to penalized Security Module marks DSR Routing packets
Penalized bit Source node picks the best path
DSG Approach – Node Rejoin
Selfish nodes switch to rejoin state after certain timeout
A rejoining node broadcasts to inform its neighbors
Each neighboring node monitors the target rejoining node
The node is switched back to Normal state if it forwards enough packets
DSG Approach - Analysis On-demand selfish node detection
Saves energy Instant selfish node avoidance Minimum control packets
transmission No need to inform nodes about a
selfish node Node rejoin supported
DSG Approach - FSM
Penalize packet received
Normal
Rejoin
Detecting
Penalized
Too many packets lost, or detecting packet received
Enough packets forwarded, or timeout
Penalize packet received
timeout
Random time, or selfish node detected
Experiment Preliminary experimental results
illustrate a 60% increase in throughput under 30% malicious nodes configuration
Most of the TCP sessions closed
Conclusion Collaboration is vital to the good
performance of Mobile Ad Hoc network
Existing techniques cannot solve the problem well enough
DSG Approach incurs minimum overhead, requires minimum energy consumption