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Routing algorithm
- 1. Routing Algorithm 2004.11. 3 Ahn Kook Jin
- 2. Contents Routing Protocoland Algorithm Classifications Link State Routing Algorithm Distance Vector Routing Algorithm LS Algorithm vs. DV Algorithm Hierarchical Routing
- 3. Routing Protocol andAlgorithm Determining the path(route) source host destination host 5 2 1 2 3 1 3 5 2 1 B A C E D F first-hop router default router source router destination router least-cost path
- 4. Classifications Global vs.decentralized global(link state algorithm) : complete information about connectivity and link costs Static vs. dynamic static : routes change very slowly Load-sensitive vs. load-insensitive load-sensitive : link costs reflect congestion Typical used Dynamic link state routing algorithm Dynamic distance vector routing algorithm
- 5. Link State RoutingAlgorithm Each node broadcasts the identities and costs to its directly attached neighbors Dijkstra’s algorithm
- 6. Link State RoutingAlgorithm Oscillation(page 307) D B C A e 1 1 2+e 0 0 1+e 0 0 0 1 1 0 0 0 e 0 1+e 0 0 0 0 0 1+e 1 2+e 0 2+e 0 0 1+e 0 0 0 1
- 7. Distance Vector RoutingAlgorithm Iterative, asynchronous, distributed Distance table D X (Y,Z) : cost of the direct link from X to Z + Z’s currently known minmum-cost path to Y D X (Y,Z)=c(X,Z)+min w {D z (Y,w)}
- 8. Distance Vector RoutingAlgorithm Initialization: D X (*,v) = inifinite, D X (v,v)=c(x,v) Send min w D X (y,w) to each neighbor when they changes C(X,V) changes Neighbor node send its update
- 9. Distance Vector RoutingAlgorithm 7 2 1 Y X Z 7 ∞ Z ∞ 2 Y Z Y D X 1 ∞ Z ∞ 2 X Z X D Y 1 ∞ Y ∞ 7 X Y X D z
- 10. Distance Vector RoutingAlgorithm 7 2 1 Y X Z 7 3 Z 8 2 Y Z Y D X 1 9 Z 8 2 X Z X D Y 1 9 Y 3 7 X Y X D z
- 11. Distance Vector RoutingAlgorithm 7 2 1 Y X Z 7 3 Z 8 2 Y Z Y D X 1 5 Z 4 2 X Z X D Y 1 9 Y 3 7 X Y X D z
- 12. Distance Vector RoutingAlgorithm Decrease 50 4 1 1 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
- 13. Distance Vector RoutingAlgorithm Decrease 50 4 1 1 Y X Z 6 1 X Z X D Y 5 50 X Y X D z
- 14. Distance Vector RoutingAlgorithm Decrease 50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
- 15. Distance Vector RoutingAlgorithm Decrease 50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
- 16. Distance Vector RoutingAlgorithm Increase 50 4 1 60 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
- 17. Distance Vector RoutingAlgorithm Increase 50 4 1 60 Routing loop Y X Z 6 60 X Z X D Y 5 50 X Y X D z
- 18. Distance Vector RoutingAlgorithm Increase 50 4 1 60 Y X Z 6 60 X Z X D Y 7 50 X Y X D z
- 19. Distance Vector RoutingAlgorithm Increase 50 4 1 60 Y X Z 8 60 X Z X D Y 7 50 X Y X D z
- 20. Distance Vector RoutingAlgorithm Increase 50 4 1 60 Too many iterations! (count-to-infinity problem) Y X Z 8 60 X Z X D Y 9 50 X Y X D z
- 21. Distance Vector RoutingAlgorithm Poisoned reverse 50 4 1 60 Y X Z ∞ 4 X Z X D Y 5 50 X Y X D z
- 22. Distance Vector RoutingAlgorithm Poisoned reverse 50 4 1 60 Y X Z ∞ 60 X Z X D Y 5 50 X Y X D z
- 23. Distance Vector RoutingAlgorithm Poisoned reverse 50 4 1 60 Y X Z ∞ 60 X Z X D Y 61 50 X Y X D z
- 24. Distance Vector RoutingAlgorithm Poisoned reverse 50 4 1 60 Y X Z 51 60 X Z X D Y 61 50 X Y X D z
- 25. Distance Vector RoutingAlgorithm Poisoned reverse Cannot solve general count-to-infinity problem 50 4 1 60 Y X Z 51 60 X Z X D Y ∞ 50 X Y X D z
- 26. LS Algorithm vs.DV Algorithm Bad Good Robustness Slow(count-to-infinity problem) O(n 2 ) algorithm Speed of convergence Maybe small O(nE) Message complexity DV LS
- 27. Hierarchical Routing Viewnetwork as interconnected routers Scale Administrative autonomy Organize routers into autonomy systems(AS)
- 28. Hierarchical Routing Autonomysystem(AS) Gateway router Intra-AS Inter-AS B.a B.a A.a A.b A.c A.d C.b C.c C.a Host H1 Host H2
- 29. Hierarchical Routing Topologicalview for inter-AS routing protocol B.a A.a A.c C.a
- 30.