1. Rumor Routing Algorithm For Sensor Networks
David Braginsky and Deborah Estrin
WSNA’02
By Kuo, Tsung-Ming

2. Outline Introduction Motivation Flooding mechanism
Rumor Routing Algorithm
Simulation results
Conclusion

3. Introduction

4. Motivation Sometimes a non-optimal route is satisfactory
When a query is generated it can be sent on a random walk until it finds the event path
query

5. Related work
Gossip routing => reliable network broadcast (multicast)
Directed diffusion => flooding

6. Flooding mechanism Query flooding Event Flooding
Expensive for high query/event ratio
Allows for optimal reverse path setup
Event Flooding
Whenever a node witnesses an event, it can flood the network
All other nodes can form gradients toward the event
Expensive for low query/event ratio

7. Flooding mechanism-compare

8. Rumor Routing Algorithm
Monte-Carlo simulations: Two lines in a bounded rectangle have a 69% chance of intersecting
Five paths leading to an event will have a 99.7% chance meet
When a query is generated it can be sent on a random walk until it finds the event path
Event
Source

9. Rumor Routing Algorithm- exam1

10. Rumor Routing Algorithm-for node
Any node may generate a query:
Has a route to the event => transmit the query
Forward the query in a random direction => search the route to event
TTL expires, the query reaches target event
If a query does not reach Event:
Retransmitting
Give up
Under most circumstances the percent of undelivered queries is very low => flooding the query

11. Rumor Routing Algorithm- exam2

12. Rumor Routing Algorithm- exam3

13. Rumor Routing Algorithm-for node
When a node witnesses an event :
Adds it to its event table
Set a distance of zero to the event
It also probabilistically generates an agent packet E

14. Rumor Routing Algorithm-for agent
When a node witnesses an event :
Adds it to its event table
Set a distance of zero to the event
It also probabilistically generates an agent packet
agent E
agent
agent

15. Rumor Routing Algorithm-for agent
When a node witnesses an event :
Adds it to its event table
Set a distance of zero to the event
It also probabilistically generates an agent packet E
agent

16. Rumor Routing Algorithm-for agent
Agent packet:
A long-lived packet
Contains an events table
Travels the network for some number of hops (TTL) and then dies
Propagating information about local events to distant nodes
It inform every node that it visits of any events in its route

17. Rumor Routing Algorithm-for agent
How to determine the agent’s next-hop:
Agent maintains a list of recently seen nodes
It will first choose nodes not in the list as the next-hop
eliminates most loops
create fairly straight paths through the network

18. Rumor Routing Algorithm- exam4

19. Rumor Routing Algorithm- exam4

20. Simulation result Node N = {3000,4000,5000} 200 X 200 m2
Node transmission range is 5m
Event E = {10,50,100}
Events of circular shape with radius of 5m
1000 queries, each from a random node to a random event

21. Simulation result Naïve Solutions Rumor Routing (1000 queries)
Et=Es + Q*(Eq + N*(1000-Qf)/1000)
Es = avg. energy to set up path
Eq = avg. energy to route a query
Qf = successful queries
Q queries are routed
Query Flooding
Et=Q*N
Event Flooding
Et=E*N

22. Simulation result A is the number of event agents generated
La is Agent TTL
Lq is Query TTL

23. Simulation Results Bad : Agent TTL 100 number of agents (around 25)
Large value of number of agents (around 400) had high setup cost but better delivery rate(99.9%), so lower average energy consumption
Best Result
Agents = 31
Agent TTL 1000
98.1 % queries delivered
1/40 of a network flood

24. Simulation result Algorithm Stability Fault Tolerance
At about 5% node failure we can expect 90% of the queries to be delivered

25. Conclusion
Rumor Routing algorithm provides a good method for delivering queries to events in large networks