Enforce Collaboration in Mobile Ad Hoc Network

Ning JiangSchool of EECS

University of Central Floridanjiang@cs.ucf.edu

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