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

Outline Introduction Motivation Flooding mechanism Rumor Routing Algorithm Simulation results Conclusion

Introduction

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

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

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

Flooding mechanism-compare

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

Rumor Routing Algorithm- exam1

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

Rumor Routing Algorithm- exam2

Rumor Routing Algorithm- exam3

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

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

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

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

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

Rumor Routing Algorithm- exam4

Rumor Routing Algorithm- exam4

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

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

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

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

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

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