1. Anonymous Gossip Improving Multicast Reliability in Mobile Ad Hoc Networks
Ranveer Chandra
Ramasubramanian Venugopalan
Ken Birman
Dept. of Computer Science,
Cornell University.

2. Introduction Mobile ad hoc network Harsh working conditions
wireless mobile devices capable of direct peer to peer communication.
deployable without fixed infrastructure.
Harsh working conditions
low bandwidth connections.
restricted power supply.

3. Multicast in Ad Hoc Networks
Applications of ad hoc networks.
disaster relief and rescue missions.
military coordination.
sensor networks.
Multicast is inevitable!
On demand multicast routing protocols.
MAODV, AMRIS. (tree based)
ODMRP, MCEDAR. (mesh based)

4. Reliable Multicast!
Messages not delivered to some members of the group.
mobility and congestion.
transient partitions.
maintenance of multicast structure.
No attempt to recover lost messages.

5. Classical Gossip + = Works in background with multicast protocol.
Probabilistic
Reliability =
Works in background with multicast protocol.
Members “gossip” randomly with other members to recover lost messages.
Probabilistic reliability guarantees.
see “Epidemic Algorithms…”, Demers et al.
see “Bimodal Multicast…”, Birman et al.

6. Classical Gossip S D

7. Classical Gossip Anonymous Gossip
Members should have complete or partial knowledge of other group members.
Impracticable in ad-hoc networks.
no organized hierarchies.
increased volatility in membership.
Anonymous Gossip
Our Protocol

8. Anonymous Gossip No knowledge of group membership is necessary.
Uses underlying multicast structure to direct gossip requests.
Each node chooses a random neighbor to forward gossip requests.
Gossip replies are sent back directly.

9. Anonymous Gossip S D

10. Optimization I: Informed Gossip
Circuitous gossip paths discovered.
Multicast structure may be broken.
Gossip with members discovered in earlier rounds of anonymous gossip.
Unicast gossip requests as well as replies.
Gossip across virtual partitions.

11. Informed Gossip S D

12. Optimization II: Gossip with Locality
Gossip with nearer members.
receive gossip replies faster.
reduce traffic overhead.
Gossip with distant members.
recover from regional losses.
High probability: gossip with nearer members.
Low probability: gossip with distant members.

13. AG: The Complete Protocol
Anonymous
Gossip
Informed
Gossip 
locality
Multicast Protocol

14. Simulation MAODV: underlying multicast protocol.
GloMoSim: network simulator.
Random waypoint: mobility model.
Every third node is a group member.
Node 1 sends 2201 packets over 440s.
10 runs with different seeds.

15. Packet Delivery vs. Transmission Range.

16. Packet Delivery vs. Max Speed

17. Packet Delivery vs. Number of nodes.

18. Goodput Ratio of AG

19. Analysis Increases packet delivery of MAODV.
Smoothens variation in packet delivery at different nodes.
Scalable with size of network.
Can work with unidirectional links.
Extra message overhead.
Latency in recovering lost messages.

20. Conclusions AG improves performance significantly.
Can be applied to tree based and mesh based on-demand multicast protocols.
Can be applied in wire line networks.