1. A Highly Adaptive Distributed Routing Algorithm for Mobile Wireless Networks Temporally-Ordered Routing Algorithm (TORA) IEEE INFOCOM 112/4/20031Authors :Vincent D. Parka,M. Scott Corson University of Maryland, USA Speaker: Chang Pei-Chen Wireless & Mobile Network Lab TamKang University

2. Overview Introduction Temporally-Ordered Routing Algorithm Conclusion

3. TORA - Overview Each destination,TORA maintains a DAG A C E D F G B A C D EF G A C E D F G B A B C D EF G DEST Increase the height

4. Introduction - Network Considerations A Collection of Mobile Wireless Routers Connection status dependent on: Node position Transmission power Antenna patterns Interference levels Result in an Unpredictable, Dynamic network Link Congestion

5. Introduction - Desirable Attributes of a Routing Algorithm Executes Distributed Provides loop-free routes Provides multiple routes (to alleviate congestion) Establishes routes quickly (so they may be used before the topology changes) Minimizes communication overhead by localizing algorithmic reaction to topological Changes when possible (to conserve available bandwidth and increase scalability)

6. Introduction - TORA Attributes On demand, Source initiated routing Distributed in that nodes only maintain one hop knowledge Provides multiple routes to alleviate congestion Creates loop free routes Handles partitions by erasing invalid routes

15. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (-,-,-,-,F) (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) Node C requires a route to Node F

16. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) It broadcasts a QRY packet. Circle around indicates RR i is Ture QTY

17. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) Sets RRi Flag Rebroadcasts the QRY Packet. QTY

18. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) Node B, D, H propagate the QRY Packet QTY

19. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) Node B, D, Sets RRi Flag and Rebroadcast the QRY Packet QTY

20. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,H) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) At the Same Time QTY Node D propagate the QTY Packet and Follow the Rule 3 Node D sets it height to Hi=(0,0,0,1,H) and broadcasts the UPD Packet (0,0,0,1,H) UPD

21. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (-,-,-,-,E) (0,0,0,0,F) DEST (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) QTY (0,0,0,1,H) UPD Node D follow the QTY Rule 2 Node E follow the QTY Rule 3 Node H follow the QTY Rule 4 (0,0,0,1,E) UPD

23. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (0,0,0,0,F) DEST (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,C) (0,0,0,1,H) UPD Node D and G follow the UPD Rule 1 (0,0,0,1,E) UPD (0,0,0,2,D) (0,0,0,2,G) UPD

24. Route Creation C AB D E F H G (-,-,-,-,B) (-,-,-,-,A) (0,0,0,0,F) DEST (-,-,-,-,C) (0,0,0,1,H) Node G, B and A follow the UPD Rule,1 (0,0,0,1,E) (0,0,0,2,D) (0,0,0,2,G) UPD (0,0,0,3,C) (0,0,0,2,B) (0,0,0,3,A)

25. Route Creation C AB D E F H G (0,0,0,0,F) DEST (0,0,0,1,H) Node A follow the UPD Rule,1 (0,0,0,1,E) (0,0,0,2,D) (0,0,0,2,G) UPD (0,0,0,3,C) (0,0,0,2,B) (0,0,0,3,A)

26. Route Creation C AB D E F H G (0,0,0,0,F) DEST (0,0,0,1,H) (0,0,0,1,E) (0,0,0,2,D) (0,0,0,2,G) UPD (0,0,0,3,C) (0,0,0,2,B)

38. Erasing Routing Erasing Routing is performed when network partition is detected When network partition is detected,” Clear packet ” (CLR) is flooding throughout the network to erase invalid routes.

47. Summary (TORA algorithm )Link reversal mechanism Advantage Loop-Free Multipath routing protocol Minimizes communication overhead Rapidly adapts to topological changes Detects network partitions and erase all invalid routes within a finite time Localize its reaction to topological changes Drawback: It does not select optimal path Limited primarily by storage complexity, which only grows linearly with the number of nodes in the network

48. Conclusions Proposed a highly adaptive distributed routing algorithm that well-suited in mobile wireless networks Decouple the generation of far-reaching control message propagation from the dynamics of the network topology Possible enhancement would be to periodically propagate refresh packets outwards from the dest. The refresh process permits intro of far-reaching control message propagation into the protocol independent of the network topology