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Contents Routing Protocol and Algorithm Classifications Link State Routing Algorithm Distance Vector Routing Algorithm LS Algorithm vs. DV Algorithm Hierarchical Routing

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Routing Protocol and Algorithm Determining the path(route) B A CE D F source host destination host first-hop router default router source router destination router least-cost path

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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

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Link State Routing Algorithm Each node broadcasts the identities and costs to its directly attached neighbors Dijkstra s algorithm

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Link State Routing Algorithm Oscillation(page 307) DB C A e 11 2+e e e e e

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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)}

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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

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Distance Vector Routing Algorithm YXZ 7 21 DXDX YZ Y2 Z7 DYDY XZ X2 Z1 DzDz XY X7 Y1

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Distance Vector Routing Algorithm YXZ 7 21 DXDX YZ Y28 Z37 DYDY XZ X28 Z91 DzDz XY X73 Y91

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YXZ 7 21 DXDX YZ Y28 Z37 DYDY XZ X24 Z51 DzDz XY X73 Y91

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YXZ DYDY XZ X46 DzDz XY X 5 1 Decrease

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Distance Vector Routing Algorithm YXZ DYDY XZ X16 DzDz XY X 5 1 Decrease

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Distance Vector Routing Algorithm YXZ DYDY XZ X16 DzDz XY X 2 1 Decrease

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Distance Vector Routing Algorithm YXZ DYDY XZ X16 DzDz XY X 2 1 Decrease

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Distance Vector Routing Algorithm Increase YXZ DYDY XZ X46 DzDz XY X 5 60

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Distance Vector Routing Algorithm Increase YXZ DYDY XZ X606 DzDz XY X Routing loop

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Distance Vector Routing Algorithm Increase YXZ DYDY XZ X606 DzDz XY X507 60

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Distance Vector Routing Algorithm Increase YXZ DYDY XZ X608 DzDz XY X507 60

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Distance Vector Routing Algorithm Increase YXZ DYDY XZ X608 DzDz XY X Too many iterations! (count-to-infinity problem)

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Distance Vector Routing Algorithm Poisoned reverse YXZ DYDY XZ X4 DzDz XY X505 60

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Distance Vector Routing Algorithm Poisoned reverse YXZ DYDY XZ X60 DzDz XY X505 60

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Distance Vector Routing Algorithm Poisoned reverse YXZ DYDY XZ X60 DzDz XY X

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Distance Vector Routing Algorithm Poisoned reverse YXZ DYDY XZ X6051 DzDz XY X

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Distance Vector Routing Algorithm Poisoned reverse Cannot solve general count-to-infinity problem YXZ DYDY XZ X6051 DzDz XY X50 60

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LS Algorithm vs. DV Algorithm LSDV Message complexity O(nE)Maybe small Speed of convergence O(n 2 ) algorithmSlow(count-to-infinity problem) RobustnessGoodBad

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Hierarchical Routing View network as interconnected routers Scale Administrative autonomy Organize routers into autonomy systems(AS)

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Hierarchical Routing B.a A.a A.b A.cA.d C.b C.c C.a Host H1 Host H2 Autonomy system(AS) Gateway router Intra-AS Inter-AS

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Hierarchical Routing B.aA.aA.cC.a Topological view for inter-AS routing protocol

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