Routing algorithm
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Routing algorithm

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algorithm comparision

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    Routing algorithm Routing algorithm Presentation Transcript

    • Routing Algorithm 2004. 11. 3 Ahn Kook Jin
    • Contents
      • Routing Protocol and Algorithm
      • Classifications
      • Link State Routing Algorithm
      • Distance Vector Routing Algorithm
      • LS Algorithm vs. DV Algorithm
      • Hierarchical Routing
    • Routing Protocol and Algorithm
      • 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
    • 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
    • Link State Routing Algorithm
      • Each node broadcasts the identities and costs to its directly attached neighbors
      • Dijkstra’s algorithm
    • Link State Routing Algorithm
      • 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
    • Distance Vector Routing Algorithm
      • 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)}
    • Distance Vector Routing Algorithm
      • 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
    • 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
    • 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
    • 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
    • Distance Vector Routing Algorithm
      • Decrease
      50 4 1 1 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Decrease
      50 4 1 1 Y X Z 6 1 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Decrease
      50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Decrease
      50 4 1 1 Y X Z 6 1 X Z X D Y 2 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Increase
      50 4 1 60 Y X Z 6 4 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Increase
      50 4 1 60 Routing loop Y X Z 6 60 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Increase
      50 4 1 60 Y X Z 6 60 X Z X D Y 7 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Increase
      50 4 1 60 Y X Z 8 60 X Z X D Y 7 50 X Y X D z
    • Distance Vector Routing Algorithm
      • 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
    • Distance Vector Routing Algorithm
      • Poisoned reverse
      50 4 1 60 Y X Z ∞ 4 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Poisoned reverse
      50 4 1 60 Y X Z ∞ 60 X Z X D Y 5 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Poisoned reverse
      50 4 1 60 Y X Z ∞ 60 X Z X D Y 61 50 X Y X D z
    • Distance Vector Routing Algorithm
      • Poisoned reverse
      50 4 1 60 Y X Z 51 60 X Z X D Y 61 50 X Y X D z
    • Distance Vector Routing Algorithm
      • 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
    • 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
    • Hierarchical Routing
      • View network as interconnected routers
        • Scale
        • Administrative autonomy
      • Organize routers into autonomy systems(AS)
    • 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
    • Hierarchical Routing Topological view for inter-AS routing protocol B.a A.a A.c C.a
    • END