Marco Conti, Enrico Gregori, Giovanni Turi Istituto di Informatica e Telematica – CNR MobiHoc ‘ Jongsoo Lee A Cross-Layer Optimization of Gnutella for Mobile Ad hoc Network

2/21 Content Introduction Why P2P in Ad-hoc network? Problems Gnutella Cross-Layer Gnutella Conclusion

3/21 Many P2P systems provide large-scale data sharing Interesting features Self-configuration Self-healing Complete decentralization Ad-hoc network need many similar features Why P2P in Ad-hoc network?

4/21 Problems Most P2P system designed for Internet. Ad-hoc network has many dynamics Current P2P system + Ad-hoc network → severe performance degradation Cross-layer architecture

5/21 Content Introduction Gnutella Architecture Algorithm Performance evaluation Cross-Layer Gnutella Conclusion

6/21 Architecture Content-based P2P system Servent works as server and client Parameters Lower bound (LB) Upper bound (UB) State Connecting Connected Full N 6 Boot : 2 LB : 2 UB : 6 TTL : 2 7 ConnectingFullConnected

7/21 Architecture Messages Ping : discover hosts on the network ־Probe and Discovery Pong : response to a Ping ־Address of connected servent, Amount of data Query/QueryHit Push Pong Cache Significantly reduce the discovery overhead local cache contains enough items → answer using local cache

8/21 Performance evaluation Modifications Remember fully connected peers Re-consider unconnected boot-servers as possible candidates Simulation environment Network Simulator2 Routing protocols ־AODV ־OLSR MAC NameDefault Value Probe interval Probe retries Discovery Ping interval Pong cache threshold (PT) Pong cache entry lifetime Lower bound (LB) Upper bound (UB) 30 sec 2 3 sec 5 10 sec 4 8

9/21 Network size Routing AODV(2KB) < OLSR(18KB) Gnutella AODV > OLSR Average connection is 3.7 Eventual overlay partitioning → Available peers is not enough AODV OLSR

10/21 Network mobility slow[1, 5] m/s & pause up to 10 sec fast[5, 15] m/s & pause up to 5 sec AODV OLSR Network mobility make partitioning! ↓ severe performance degradation

11/21 Network partitioning Partitioning make peer to connecting state Broader discovery

12/21 Content Introduction Gnutella Cross-Layer Gnutella Architecture Algorithm Performance evaluation Conclusion

13/21 Architecture OLSR + Gnutella → Cross-layer(XL) Gnutella OLSR show better result than AODV?. Spread OIGnutella → OLSR Advertisement local peer with the Hello or Topology Control message Recv OI OLSR → Gnutella Notify the local peer about the advertisement of a remote peer

14/21 Architecture Pong cache → Advertisement table Routing hops → Accurate physical distance Share message → Fewer network traffic XL-Gnutella can provide better overlay!

15/21 Algorithm Advertisement Connecting ־attempt a connection request Connected ־If new peer is closer than any of the connected peer, attempt a connection request Full ־If new peer is closer than any of the connected peer, remove furthest connection and attempt a connection request Expiration of advertisement Detected internally by the advertisement table Not probe ping

16/21 Network size 25-30% Larger OLSR traffic Only Query/QueryHit/Push → total traffic reduced 40% Independent from size Close to UB in 40 sec → Faster & More connection

17/21 Network mobility Fall down to 5-6 connection But Remain in [LB-UB] range

18/21 Network partitioning XL-GNU loose connectivity like GNU But… XL-GNU have no traffic burst like GNU Traffic burst

19/21 Network Churns 70% burst churning Churning make partitioning ↓ Recovery is difficult!

20/21 Path stretch & query success rate XL-GNU significantly closer to the real network less partitioning → higher query success rate

21/21 Content Introduction Gnutella Cross-Layer Gnutella Conclusion

22/21 Conclusion Cross-layer interaction between overlay peers and routing agents at network layer Better performance in Ad-hoc network Less network traffic More connectivity Lower bootstrap latencies Higher query success

23/21 Algorithm Ping Pong if ( is probe? ) Send Pong else { delete stale cache item if ( pong cache size > PT ) { Send Pong using cache } else { if ( state is not FULL? ) SendPong with my info if ( ping TTL > 1 ) Forward Ping } if ( Pong TTL + hops <= TTLmax ) { Add Pong cache if ( Pong TTL > 1 ) Forward Pong } Cache Content IP Address / Port number Number of files & kilobytes shares Hops value