Content-Based Routing in Mobile Ad Hoc Networks

1. Content-Based Routing in Mobile Ad Hoc Networks Milenko Petrovic, Vinod Muthusamy, Hans-Arno Jacobsen University of Toronto July 18, 2005 MobiQuitous 2005San Diego, CA

2. Mobile Ad Hoc Networks • Mobile Ad Hoc Network • Autonomous system of wireless mobile routers • Characteristics • Varying bandwidth, latency, connectivity • Mobile nodes, and highly dynamic topology • Applications • Interactive games, location based advertising, mobile auctions, financial services, selective information dissemination • Communication primitives • Unicast • Broadcast • Multicast Content-Based Routing in MANET

3. Content Based Routing in MANET • Content Based Routing (a.k.a. publish/subscribe) • Unicast, multicast, broadcast • No addresses loose coupling • Supports large number of fine-grained groups • Expressive group membership • Applications • Stock updates • Mobile games • Accident information dissemination Content-Based Routing in MANET

4. Agenda • Background: Publish/Subscribe • Model • Wired distributed algorithm • Benefits • Content-Based Routing • Protocols • Evaluation • Conclusions Content-Based Routing in MANET

5. Notification Notification Publish/Subscribe Model TSX Stock markets NASDAQ NYSE Publisher Publisher AMGN=58 Publications IBM=84 ORCL=12 JNJ=58 HON=24 INTC=19 MSFT=27 BrokerNetwork Subscriptions: IBM > 85 ORCL < 10 JNJ > 60 Subscriptions Subscriber Subscriber Content-Based Routing in MANET

6. Subscriber Subscriber Publisher Distributed Publish/Subscribe . . . . . . • Advertisements flooded • Create ad tree • Subscriptions propagate along reverse ad path • Create multicast tree • Publications propagate along reverse sub path Advertisements Subscriptions Publications Content-Based Routing in MANET

7. Publish/Subscribe Benefits • Simple interface • Decoupling of producers and consumers of data • Address • Content-based routing • Anonymity • Platform • Space • Time • Representation (semantic) • Efficient data dissemination (scalability) • Push model • Multicast Content-Based Routing in MANET

8. Content Based Routing in MANET • Challenges • Highly dynamic network • Fault tolerance, reliability • CBR (Content-Based Routing) • Based on wired pub/sub protocols • FT-CBR (Fault-Tolerant CBR) • Adapt to node mobility • RAFT-CBR (Reliable And Fault-Tolerant CBR) • Guaranteed delivery Content-Based Routing in MANET

9. CBR Protocol • Based on distributed pub/sub protocols • Broadcast ads • Build connectivity graph • Unicast subs • Setup multicast route • Soft state • Beacon ads and subs • Passive route repairs P S Advertisements Subscriptions Publications Content-Based Routing in MANET

10. Protocol Optimizations • Covering optimization • Common in pub/sub systems • Quench subsumed subscriptions • Most Covering (MC) optimization • Forward subscription toward existing multicast tree • Tradeoff route length for transmission and storage • Builds more stable multicast trees P S3 B S1 S2 Subscriptions Content-Based Routing in MANET

11. FT-CBR Protocol • Routes broken due to node mobility • Hop by hop reliability • Proactive route repairs • Hop by hop ACK of messages • On unack’d message • Expanding ring search to find destination node P S PublicationAcknowledgement Content-Based Routing in MANET

12. RAFT-CBR Protocol Difficulties of RAFT-CBR • End to end reliability • Difficult to ensure in CBR • No ad or sub state maintained • Reuse underlying unicast routing protocol • Assume publisher is reliable and knows subscriber set • Include (dest, seq) pair in each publication • Subscribers send cumulative ACKs and selective NACKs • Hierarchical ACK propagation P S 1 2 3 4 5 6 S1 1 3 4 5 P S2 2 5 6 P S2 S3 S1 PublicationAcknowledgement Content-Based Routing in MANET

13. Evaluation • Simulation Environment • ns-2 network simulator • Implemented CBR protocols • Shopping district scenario • Vendors advertise to shoppers in a shopping district • Shoppers interested in nearby stores • Parameters • 50 mobile nodes (subscribers) • Stationary publisher • Random publications • Metrics • Delivery ratio • Delivery delay • Message load Content-Based Routing in MANET

14. Subscriber Scalability • Delivery ratio • 75% for CBR, ~100% for FT-CBR • Delivery delay • Little change • Little change in multicast tree depth • No recovery mechanisms (CBR) • Message cost • FT-CBR high due to expanding ring search Content-Based Routing in MANET

15. Effects of Optimizations • Covering and most-covering (MC) optimizations • MC improves delivery by 10% points … • Benefits increase with more subscribers • ... but increases delay and message load • Costs diminish with larger multicast trees • Covering significantly reduces message load Content-Based Routing in MANET

16. Interest Locality • Vary number of subscribers with static interest • Leads to less stable and larger multicast trees • MC optimization has largest impact • Makes more stable (but longer) multicast trees Content-Based Routing in MANET

17. Related Work • Little research into fully content-based pub/sub protocols in MANET • Wired CBR protocols • Typically assume stable acyclic topologies • Multicast in MANET • MAODV, DVMRP, ODMRP • Group-based (not content-based) • Reliability protocols not applicable to content-based Content-Based Routing in MANET

18. Conclusions • Publish/Subscribe content based routing • Appropriate for mobile networks • No “best” protocol • CBR: Low delay, message cost • Streaming media applications • FT-CBR: Adapts to dynamic environments • High mobility applications • RAFT-CBR: Reliable • Financial applications • Future work • More protocols • Combine best of existing protocols • More experiments • Mobile subscribers, realistic scenarios, etc. Content-Based Routing in MANET

19. Q&A Content-Based Routing in Mobile Ad Hoc Networks www.msrg.utoronto.ca Content-Based Routing in MANET