1. Ad-hoc On-Demand Distance Vector Routing (AODV) Sirisha R. Medidi

2. Overview Introduction AODV Path Discovery Reverse Path Setup Forward Path Setup Example Route Table Management Path Maintenance Conclusion

3. Introduction AODV -- On-demand route discovery Effective use of available bandwidth Highly scalable Minimizes broadcasts & transmission latency

4. AODV Primary Objectives Minimalist broadcasts To separate local connectivity management & topology maintenance Disseminate local connectivity changes to active mobile nodes  Uses a broadcast route discovery mechanism as in DSR  Dynamic route table entry establishment at intermediate nodes  Most current routing information through destination sequence numbers

5. Path Discovery Initiated when a communication need arises Source node initiates path discovery by broadcasting a route request (RREQ) packet to its neighbors Every node maintains two separate counters Sequence number Broadcast-id

6. Path Discovery (Cont.) A neighbor either broadcasts the RREQ to its neighbors or satisfies the RREQ by sending a RREP back to the source Later copies of the same RREQ request are discarded

7. Reverse Path Setup Reverse path are automatically set-up Node records the address of the sender of RREQ Entries are discarded after a time-out period

8. Forward Path Setup Eventually, a RREQ arrives at a node that possesses the current route for the destination (Comparison of sequence numbers) Node unicasts a route reply packet (RREP) back to the neighbor from which it received the RREQ. The RREP travels along the path established in the reverse path set-up Each node along the RREP journey sets up a forward pointer, updates time-out entries, records the destination sequence number of requested destination.

9. AODV (Example) BSE C GFAHDYIKPLJTZ RREQ

10. AODV (Example) BSE C GFAHDYIKPLJTZ Reverse Path Setup

11. AODV (Example) BSE C GFAHDYIKPLJTZ

12. BSE C GFAHDYIKPLJTZ

13. BSE C GFAHDYIKPLJTZ RREP

14. AODV (Example) BSE C GFAHDYIKPLJTZ Forward Path Setup

15. AODV (Example) BSE C GFAHDYIKPLJTZ

16. BSE C GFAHDYIKPLJTZ

17. BSE C GFAHDYIKPLJTZ

18. Route Table Management Soft-state maintenance of route table entries Route request expiration timer Route caching timeout Active timeout period

19. Path Maintenance Varying effects (based on the type of node) with node movement Nodes not on the active path => No effect Source node => Re-initiate path discovery Destination/Intermediate nodes => Special RREP

20. Conclusion AODV -- efficient algorithm for ad-hoc networks Highly Scalable Need for broadcast is minimized Quick response to link breakage in active routes Loop free routes