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Published byRobert Short Modified over 4 years ago

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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) 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

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**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

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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) 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

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**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)}

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**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

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**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

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**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

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**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

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**Distance Vector Routing Algorithm**

Decrease DY X Z 4 6 Y 1 4 1 X Z 50 Dz X Y 50 5

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**Distance Vector Routing Algorithm**

Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 5

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**Distance Vector Routing Algorithm**

Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 2

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**Distance Vector Routing Algorithm**

Decrease DY X Z 1 6 Y 1 4 1 X Z 50 Dz X Y 50 2

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**Distance Vector Routing Algorithm**

Increase DY X Z 4 6 Y 60 4 1 X Z 50 Dz X Y 50 5

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**Distance Vector Routing Algorithm**

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

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**Distance Vector Routing Algorithm**

Increase DY X Z 60 6 Y 60 4 1 X Z 50 Dz X Y 50 7

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**Distance Vector Routing Algorithm**

Increase DY X Z 60 8 Y 60 4 1 X Z 50 Dz X Y 50 7

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**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

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**Distance Vector Routing Algorithm**

Poisoned reverse DY X Z 4 ∞ Y 60 4 1 X Z 50 Dz X Y 50 5

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**Distance Vector Routing Algorithm**

Poisoned reverse DY X Z 60 ∞ Y 60 4 1 X Z 50 Dz X Y 50 5

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**Distance Vector Routing Algorithm**

Poisoned reverse DY X Z 60 ∞ Y 60 4 1 X Z 50 Dz X Y 50 61

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**Distance Vector Routing Algorithm**

Poisoned reverse DY X Z 60 51 Y 60 4 1 X Z 50 Dz X Y 50 61

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**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 ∞

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**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

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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.c A.d C.b C.c C.a Host H1 Host H2**

Autonomy system(AS) Gateway router Intra-AS Inter-AS

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**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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END

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Announcement r Project 2 extended to 2/20 midnight r Project 3 available this weekend r Homework 3 available today, will put it online.

Announcement r Project 2 extended to 2/20 midnight r Project 3 available this weekend r Homework 3 available today, will put it online.

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