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

2. 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

3. 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

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

5. 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

6. 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)}

7. 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

8. Distance Vector Routing AlgorithmDY X Z 2 ∞ 1 Y 2 1 X Z 7 Dz X Y 7 ∞ 1 DX Y Z 2 ∞ 7

9. Distance Vector Routing AlgorithmDY 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

10. Distance Vector Routing AlgorithmDY 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

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

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

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

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

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

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

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

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

19. 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

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

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

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

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

24. 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 ∞

25. 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

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

27. 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

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

29. END