0. Part 4: Network Layer Part A: Algorithms
4/17/2017
Part 4: Network Layer Part A: Algorithms

1. Summary The Problem The Dijkstra’s Shortest Path Algorithm
Distance Vector Routing
Link State Routing
Hierarchical Routing
Routing in Ad Hoc Networks

2. 1. The Problem (1) Store-and-Forward Packet Switching
4/17/2017
Store-and-Forward Packet Switching
Services Provided to the Transport Layer
Connectionless Service
Connection-Oriented Service
Research on DTN, Localization

3. 1. The Problem (2): Packet Switching
4/17/2017
fig 5-1
Research on DTN, Localization
The environment of the network layer protocols.

4. 1. The Problem (3): Connectionless Service
4/17/2017
Research on DTN, Localization
Routing within a diagram subnet.

5. 1. The Problem (4): Connection-Oriented Service
4/17/2017
Research on DTN, Localization
Routing within a virtual-circuit subnet.

6. 1. The Problem (5): Connectionless VS. Connection-Oriented
4/17/2017
Research on DTN, Localization

7. 2 Shortest Path Algorithm
The first 5 steps used in computing the shortest path from A to D. The arrows indicate the working node.

8. 3 Distance Vector Routing (1)
(a) A subnet. (b) Input from A, I, H, K, and the new
routing table for J.

9. 3 Distance Vector Routing (2)
The count-to-infinity problem.

10. 3 Distance Vector Routing (3): Loop-Breaking Heuristics
Set infinity to a limited number, e.g. 16.
Split horizon
Split horizon with poison reverse

11. 3 Example: D A E B C Initialization A C E B D A C E B D A C E B D A C1 10 2 A B C E D A C E B D A C E B D A C E B D
Initialization

12. D A E B C Direct Neighbours A C E B D 1 A C E B D 10 2 1 2 A C E B D 210 2 1 2 1 10 2 A B C E D A C E B D 2 2 A C E B D 10 A C E B D
Direct
Neighbours 2 2

13. D A E B C Neighbours of neighbours A C E B D 1 A C E B D 11 10 2 3 1 211 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 2 2 A C E B D 10 A C E B D 3
Neighbours
of neighbours 11 2 2

14. D A E B C Neighbours of neighbours A C E B D 1 A C E B D 11 10 2 3 1 211 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 A C E B D 10 A C E B D 3
Neighbours
of neighbours 13 13 11 2 13 2

15. D A E B C Stable convergence A C E B D 1 A C E B D 11 10 2 3 1 2 A C E11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 A C E B D 10 A C E B D 3
Stable
convergence 13 13 11 2 13 2

16. D A E B C Good news: A new link! A C E B D 1 A C E B D 11 10 2 3 1 2 A11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 1 A C E B D 10 A C E B D 3
Good news:
A new link! 13 13 11 2 13 2

17. D A E B C Direct endpoints know A C E B D 1 A C E B D 11 10 2 3 1 2 A11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 1 A C E B D 10 A C E B D 3
Direct
endpoints
know 1 1 11 2 13 2

18. D A E B C Neighbours know A C E B D 1 A C E B D 3 10 2 3 1 2 A C E B D3 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 1 A C E B D 4 A C E B D 3
Neighbours
know 1 1 3 2 3 2

19. D A E B C Neighbours of neighbours know A C E B D 1 A C E B D 3 4 2 33 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 1 A C E B D 4 A C E B D 3
Neighbours
of neighbours
know 1 1 3 2 3 2

20. D A E B C A happy and stable network A C E B D 1 A C E B D 3 4 2 3 1 23 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 1 A C E B D 4 A C E B D 3
A happy and
stable network 1 1 3 2 3 2

21. D A E B C Bad news: Link crash!! A C E B D 1 A C E B D 3 4 2 3 1 2 A C3 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 A C E B D 4 A C E B D 3
Bad news:
Link crash!! 1 1 3 2 3 2

22. D A E B C Direct endpoints know A C E B D 1 A C E B D 3 4 2 3 1 2 A C3 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 A C E B D A C E B D 3
Direct
endpoints
know 2 2

23. D A E B C A C E B D 1 A C E B D 3 4 2 3 1 2 A C E B D 3 3 3 2 2 A C E3 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 A C E B D 10 A C E B D 3 2 2

24. D A E B C Get help from neighbours A C E B D 1 A C E B D 3 4 2 3 1 2 A3 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 3 2 2 A C E B D 10 A C E B D 3
Get help
from
neighbours 5 13 11 2 13 2

25. D A E B C Routing loop (due to inconsistent state info) A C E B D 1 A7 4 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 7 2 2 A C E B D 10 A C E B D 3
Routing loop
(due to
inconsistent
state info) 5 13 11 2 13 2

26. D A E B C A C E B D 1 A C E B D 7 8 2 3 1 2 A C E B D 3 3 7 2 2 A C E7 8 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 7 2 2 A C E B D 10 A C E B D 3 9 13 11 2 13 2

27. D A E B C Counting to infinity… A C E B D 1 A C E B D 11 8 2 3 1 2 A C11 8 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 11 2 2 A C E B D 10 A C E B D 3
Counting
to infinity… 9 13 11 2 13 2

28. D A E B C A C E B D 1 A C E B D 11 10 2 3 1 2 A C E B D 3 3 11 2 2 A C11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 11 2 2 A C E B D 10 A C E B D 3 13 13 11 2 13 2

29. D A E B C A C E B D 1 A C E B D 11 10 2 3 1 2 A C E B D 3 3 13 2 2 A C11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 A C E B D 10 A C E B D 3 13 13 11 2 13 2

30. D A E B C Stability again A C E B D 1 A C E B D 11 10 2 3 1 2 A C E B11 10 2 3 1 2 1 10 2 A B C E D A C E B D 3 3 13 2 2 A C E B D 10 A C E B D 3
Stability
again 13 13 11 2 13 2

31. 4 Link State Routing (1) Each router must do the following:
Discover its neighbors, learn their network address.
Measure the delay or cost to each of its neighbors.
Construct a packet telling all it has just learned.
Send this packet to all other routers.
Compute the shortest path to every other router.

32. 4 Link State Routing (2): Learning about the Neighbors
Nine routers and a LAN.
A graph model of (a).

33. 4 Link State Routing (3): Measuring Line Cost
A subnet in which the East and West parts are connected by two lines.

34. 4 Link State Routing (4): Building Link State Packets
(a) A subnet. (b) The link state packets for this subnet.

35. 4 Link State Routing (5): Distributing the Link State Packets
The packet buffer for router B in the previous slide (Fig ).

36. 5 Hierarchical Routing
Hierarchical routing.

37. 6. Routing in Ad Hoc Networks (1)
Possibilities when the routers are mobile:
Military vehicles on battlefield.
No infrastructure.
A fleet of ships at sea.
All moving all the time
Emergency works at earthquake .
The infrastructure destroyed.
A gathering of people with notebook computers.
In an area lacking

38. 6. Routing in Ad Hoc Networks (2): Route Discovery
(a) Range of A's broadcast.
(b) After B and D have received A's broadcast.
(c) After C, F, and G have received A's broadcast.
(d) After E, H, and I have received A's broadcast.
Shaded nodes are new recipients. Arrows show possible reverse routes.

39. 6. Routing in Ad Hoc Networks (3): Route Discovery
Format of a ROUTE REQUEST packet.

40. 6. Routing in Ad Hoc Networks (4): Route Discovery
Format of a ROUTE REPLY packet.

41. 6. Routing in Ad Hoc Networks (5): Route Maintenance
(a) D's routing table before G goes down.
(b) The graph after G has gone down.