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Routing algorithm

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Routing algorithm

  1. 1. Routing Algorithm 2004. 11. 3 Ahn Kook Jin
  2. 2. Contents <ul><li>Routing Protocol and Algorithm </li></ul><ul><li>Classifications </li></ul><ul><li>Link State Routing Algorithm </li></ul><ul><li>Distance Vector Routing Algorithm </li></ul><ul><li>LS Algorithm vs. DV Algorithm </li></ul><ul><li>Hierarchical Routing </li></ul>
  3. 3. Routing Protocol and Algorithm <ul><li>Determining the path(route) </li></ul>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. 4. Classifications <ul><li>Global vs. decentralized </li></ul><ul><ul><li>global(link state algorithm) : complete information about connectivity and link costs </li></ul></ul><ul><li>Static vs. dynamic </li></ul><ul><ul><li>static : routes change very slowly </li></ul></ul><ul><li>Load-sensitive vs. load-insensitive </li></ul><ul><ul><li>load-sensitive : link costs reflect congestion </li></ul></ul><ul><li>Typical used </li></ul><ul><ul><li>Dynamic link state routing algorithm </li></ul></ul><ul><ul><li>Dynamic distance vector routing algorithm </li></ul></ul>
  5. 5. Link State Routing Algorithm <ul><li>Each node broadcasts the identities and costs to its directly attached neighbors </li></ul><ul><li>Dijkstra’s algorithm </li></ul>
  6. 6. Link State Routing Algorithm <ul><li>Oscillation(page 307) </li></ul>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. 7. Distance Vector Routing Algorithm <ul><li>Iterative, asynchronous, distributed </li></ul><ul><li>Distance table </li></ul><ul><ul><li>D X (Y,Z) : cost of the direct link from X to Z + Z’s currently known minmum-cost path to Y </li></ul></ul><ul><ul><li>D X (Y,Z)=c(X,Z)+min w {D z (Y,w)} </li></ul></ul>
  8. 8. Distance Vector Routing Algorithm <ul><li>Initialization: </li></ul><ul><ul><li>D X (*,v) = inifinite, D X (v,v)=c(x,v) </li></ul></ul><ul><li>Send min w D X (y,w) to each neighbor when they changes </li></ul><ul><ul><li>C(X,V) changes </li></ul></ul><ul><ul><li>Neighbor node send its update </li></ul></ul>
  9. 9. Distance Vector Routing Algorithm 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. 10. Distance Vector Routing Algorithm 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. 11. Distance Vector Routing Algorithm 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. 12. Distance Vector Routing Algorithm <ul><li>Decrease </li></ul>50 4 1 1 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
  13. 13. Distance Vector Routing Algorithm <ul><li>Decrease </li></ul>50 4 1 1 Y X Z 6 1 X Z X D Y 5 50 X Y X D z
  14. 14. Distance Vector Routing Algorithm <ul><li>Decrease </li></ul>50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
  15. 15. Distance Vector Routing Algorithm <ul><li>Decrease </li></ul>50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
  16. 16. Distance Vector Routing Algorithm <ul><li>Increase </li></ul>50 4 1 60 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
  17. 17. Distance Vector Routing Algorithm <ul><li>Increase </li></ul>50 4 1 60 Routing loop Y X Z 6 60 X Z X D Y 5 50 X Y X D z
  18. 18. Distance Vector Routing Algorithm <ul><li>Increase </li></ul>50 4 1 60 Y X Z 6 60 X Z X D Y 7 50 X Y X D z
  19. 19. Distance Vector Routing Algorithm <ul><li>Increase </li></ul>50 4 1 60 Y X Z 8 60 X Z X D Y 7 50 X Y X D z
  20. 20. Distance Vector Routing Algorithm <ul><li>Increase </li></ul>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. 21. Distance Vector Routing Algorithm <ul><li>Poisoned reverse </li></ul>50 4 1 60 Y X Z ∞ 4 X Z X D Y 5 50 X Y X D z
  22. 22. Distance Vector Routing Algorithm <ul><li>Poisoned reverse </li></ul>50 4 1 60 Y X Z ∞ 60 X Z X D Y 5 50 X Y X D z
  23. 23. Distance Vector Routing Algorithm <ul><li>Poisoned reverse </li></ul>50 4 1 60 Y X Z ∞ 60 X Z X D Y 61 50 X Y X D z
  24. 24. Distance Vector Routing Algorithm <ul><li>Poisoned reverse </li></ul>50 4 1 60 Y X Z 51 60 X Z X D Y 61 50 X Y X D z
  25. 25. Distance Vector Routing Algorithm <ul><li>Poisoned reverse </li></ul><ul><li>Cannot solve general count-to-infinity problem </li></ul>50 4 1 60 Y X Z 51 60 X Z X D Y ∞ 50 X Y X D z
  26. 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. 27. Hierarchical Routing <ul><li>View network as interconnected routers </li></ul><ul><ul><li>Scale </li></ul></ul><ul><ul><li>Administrative autonomy </li></ul></ul><ul><li>Organize routers into autonomy systems(AS) </li></ul>
  28. 28. Hierarchical Routing Autonomy system(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. 29. Hierarchical Routing Topological view for inter-AS routing protocol B.a A.a A.c C.a
  30. 30. END

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