1. Routing with Congestion Awareness and Adaptivity in Mobile Ad hoc Networks Duc A. Tran and Harish Raghavendra Multimedia and Collaborative Networking Group Department of Computer Science University of Dayton IEEE WCNC 2005

2. Outline  Introduction  Congestion Adaptive Routing  Performance Study  Conclusion

3. Introduction  Routing categories proactive v.s. on-demand single-path v.s. multi-path congestion-adaptive v.s. congestion- unadaptive  Congestion unawareness leads to Long latency High overhead Many packet losses

4. Congestion Adaptive Routing  Congestion-adaptive Routing Protocol (CRP) is on-demand and unicast routing protocol Congestion Monitoring Primary Route Discovery Bypass Discovery Traffic Splitting and Congestion Adaptability Multi-path Minimization Failure Recovery

5. Congestion Adaptive Routing ---- Congestion Monitoring  A node periodically checks the occupancy of its link-layer buffer. (ratio r) r ≦ 1/2,a node is said to be “ green ” 1/2 ＜ r ≦ 3/4,a node is said to be “ yellow ” 3/4 ＜ r ≦ 1,a node is said to be “ red ”

6. Congestion Adaptive Routing ---- Primary Route Discovery  Primary Route REQ packet and REP packet  Each node has two table primary table and bypass table  Reduce primary route discovery drop REQ packet if arriving at a node with a ” red ” status. forward REQ to next primary node if a previous connection establishment.  Remove the entry of primary table If no data packet destined for R arrives or next primary node is not heard of after a certain timeout period.

8. Congestion Adaptive Routing ---- Bypass Discovery  A node N periodically broadcast a UDT(update) packet with TTL=1 N ’ s congestion status a set of tuples [destination R, next green node G,distance to green node m]

9. Congestion Adaptive Routing ---- Bypass Discovery  bypass search is similar to primary route search except the bypass request packet ’ s TLL=2m bypass request is dropped if arriving at a node already present on the primary route

10. Congestion Adaptive Routing ---- Traffic Splitting and Congestion Adaptability  as long as the next primary node is not red, no packet is forwarded on the bypass.

11. 1.00.50.80.41.0 0.5 0.2 0.6 0.25 0.75 0.625 0.375 0.85 0.15 05-(1-0.5)/20.25+(1-0.25)/2 Congestion Adaptive Routing ---- Traffic Splitting and Congestion Adaptability 0.8+(1-0.8)/4

12. Congestion Adaptive Routing ---- Multi-path Minimization  If prTab[N,R].prob approaches 1.0 N removes the bypass.  If prTab[N,R].prob approaches 0 the bypass becomes primary.  CRP does not allow a node to use more than one bypass  Short bypass lengths

13. Congestion Adaptive Routing ---- Failure Recovery

16. Performance Study  Simulator :Ns-2  50 nodes in a 1500m x 300m  Bit rate:2Mbps  Radio range:250m  MAC layer:802.11 DCF  Each simulation run 300 seconds  CBR:512-byte date packets  Rate:1,5,10,20,40 packet/s

17. Performance Study

24. Conclusion  CRP is its adaptability to congestion.  CRP enjoys fewer packet losses  CRP does not incur heavy overhead  Our future work will be focused on optimization techniques for CRP and how different congestion predication and control mechanisms cooperate with CRP