# Contents Routing Protocol and Algorithm Classifications

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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

Routing Protocol and Algorithm
Determining the path(route) destination router first-hop router default router destination host 5 2 1 3 B A C E D F source host least-cost path source router

Classifications Global vs. decentralized Static vs. dynamic
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+e 1 2+e 1 e 1+e 2+e 1+e 1 2+e 1+e 1

Distance Vector Routing Algorithm
Iterative, asynchronous, distributed Distance table DX(Y,Z) : cost of the direct link from X to Z + Z’s currently known minmum-cost path to Y DX(Y,Z)=c(X,Z)+minw{Dz(Y,w)}

Distance Vector Routing Algorithm
Initialization: DX(*,v) = inifinite, DX(v,v)=c(x,v) Send minwDX(y,w) to each neighbor when they changes C(X,V) changes Neighbor node send its update

Distance Vector Routing Algorithm
DY X Z 2 1 Y 2 1 X Z 7 Dz X Y 7 1 DX Y Z 2 7

Distance Vector Routing Algorithm
DY X Z 2 8 9 1 Y 2 1 X Z 7 Dz X Y 7 3 9 1 DX Y Z 2 8 3 7

Distance Vector Routing Algorithm
DY X Z 2 4 5 1 Y 2 1 X Z 7 Dz X Y 7 3 9 1 DX Y Z 2 8 3 7

Distance Vector Routing Algorithm
Decrease DY X Z 4 6 Y 1 4 1 X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 2

Distance Vector Routing Algorithm
Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 2

Distance Vector Routing Algorithm
Increase DY X Z 4 6 Y 60 4 1 X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Increase DY X Z 60 6 Y 60 4 1 Routing loop X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Increase DY X Z 60 6 Y 60 4 1 X Z 50 Dz X Y 50 7

Distance Vector Routing Algorithm
Increase DY X Z 60 8 Y 60 4 1 X Z 50 Dz X Y 50 7

Distance Vector Routing Algorithm
Increase DY X Z 60 8 Y 60 4 1 Too many iterations! (count-to-infinity problem) X Z 50 Dz X Y 50 9

Distance Vector Routing Algorithm
Poisoned reverse DY X Z 4 Y 60 4 1 X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Poisoned reverse DY X Z 60 Y 60 4 1 X Z 50 Dz X Y 50 5

Distance Vector Routing Algorithm
Poisoned reverse DY X Z 60 Y 60 4 1 X Z 50 Dz X Y 50 61

Distance Vector Routing Algorithm
Poisoned reverse DY X Z 60 51 Y 60 4 1 X Z 50 Dz X Y 50 61

Distance Vector Routing Algorithm
Poisoned reverse Cannot solve general count-to-infinity problem DY X Z 60 51 Y 60 4 1 X Z 50 Dz X Y 50

LS Algorithm vs. DV Algorithm
Message complexity O(nE) Maybe small Speed of convergence O(n2) algorithm Slow(count-to-infinity problem) Robustness Good Bad

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

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

Topological view for inter-AS routing protocol
Hierarchical Routing B.a C.a A.a A.c Topological view for inter-AS routing protocol

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