1. 16장. Networking and Internetworking Devices
16.1 Repeaters
16.2 Bridges
16.3 Routers
16.4 Gateways
16.5 Routing Algorithms
16.6 요약

2. Networking and Internetworking Devices(cont’d)
An internet is an interconnection of individual networks. To creates an internet, we need internetworking devices called routers and gateways.
An internet is different from the Internet.
Internet is the name of a specific worldwide network.

3. Networking and Internetworking Devices(cont’d)
Connecting device

4. Networking and Internetworking Devices(cont’d)
Connecting devices and the OSI model
Application
Gateway
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Router
Network
Data link
Bridge
Data link
Physical
Repeater
Physical

5. 16.1 Repeaters
~ is an electronic device that operates on only the physical layer of the OSI model.

6. Repeaters(cont’d)
Repeater allows us to extend only the physical length of a network.

7. Repeaters(cont’d)
Function of a repeater

8. 16.2 Bridges
~ operate in both the physical and the data link layers of the OSI model.

9. Bridges(cont’d)
Bridges divide a large network into smaller segments

10. Bridges(cont’d)
Function of a bridge

11. Bridges(cont’d) Types of Bridges Simple Bridges Learning Bridges
Multiport Bridges

12. 16.3 Routers
~ operate in the physical, data link, and network layers of the OSI model.

13. Routers(cont’d)
Routers relay packets among multiple interconnected networks.

14. Routers(cont’d) Routing concepts
~ Whenever there are multiple options, the router chooses the pathway.
Least-Cost Routing
Which path does it choose?
Decision is based on efficiency(cheapest, fastest, shortest)
Distributed Routing
Packet Lifetime(number of hops)

15. 16.4 Gateways
~ potentially operate in all seven layers of the OSI model(protocol converter).
Application
Presentation
Session
Transport
Network
Data link
Physical

16. Gateways(cont’d)
Gateway

17. 16.5 Routing Algorithms
- in routing the pathway with the lowest cost is considered the best.
- as long as the cost of each links is known, a router can find the optional combination for any transmission.
- Two common methods are used to calculate the shortest path between two routers: distance vector routing and link state routing.

18. Routing Algorithms(cont’d)
Distance Vector Router
~ each router periodically shares its knowledge about the entire network with its neighbors.
1. Knowledge about the whole network.
2. Routing only to neighbors.
3. Information sharing at regular intervals.

19. Routing Algorithms(cont’d)
Sharing Information
Example of an internet

20. Routing Algorithms(cont’d)
Concept of distance vector routing
I periodically send
my knowledge about
the whole internetwork
to A, C.
I periodically send
my knowledge about
the whole internetwork
to B, F, E.
I periodically send
my knowledge about
the whole internetwork
to B, D.
I periodically send
my knowledge about
the whole internetwork
to A.
I periodically send
my knowledge about
the whole internetwork
to A, D.
I periodically send
my knowledge about
the whole internetwork
to C, E.

21. Routing Algorithms(cont’d)
Routing table(distance vector)

22. Routing Algorithms(cont’d)
Creating the table

23. Routing Algorithms(cont’d)
Updating the table
Updating routing table for router A

24. Routing Algorithms(cont’d)
Updating routing table for router C

25. Routing Algorithms(cont’d)
Updated routing tables

26. Routing Algorithms(cont’d)
Updating routing table for router F

27. Routing Algorithms(cont’d)
New updated routing tables

28. Routing Algorithms(cont’d)
Final routing tables

29. Routing Algorithms(cont’d)
Link State Routing
~ each router shares its knowledge of its neighborhood with all routers in the network.
1. Knowledge about the neighborhood.
2. To all routers.
3. Information sharing at regular intervals.

30. Routing Algorithms(cont’d)
Information Sharing
I send information
about my neighbors
to every router.
I send information
about my neighbors
to every router.
I send information
about my neighbors
to every router.
I send information
about my neighbors
to every router.
I send information
about my neighbors
to every router.
I send information
about my neighbors
to every router.

31. Routing Algorithms(cont’d)
Packet Cost
~ is a weighted value based on a variety of factors such as security levels, traffic, or state of the link.
Cost is applied only by routers and not by any other stations on a network
Cost is applied as a packet leaves the router rather than as it enters

32. Routing Algorithms(cont’d)
Cost in link state routing

33. Routing Algorithms(cont’d)
LSP(Link State Packet)
Advertiser
Network
Cost
Neighbor
…………
…………
…………
…………

34. Routing Algorithms(cont’d)
Getting information about Neighbors(Initialization)
Flooding of A’s LSP

35. Routing Algorithms(cont’d)
Flooding of B’s LSP

36. Routing Algorithms(cont’d)
Link State Database
~ every router has exactly the same link state database

37. Routing Algorithms(cont’d)
Dijkstra Algorithm
~ calculates the shortest path between two points on a network using a graph made up of nodes and arcs.
Node : networks and routers
Arc : connection between a router and a network
Cost : applied only to the arc from router to network

38. Routing Algorithms(cont’d)
Cost in the Dijkstra Algorithm

39. Routing Algorithms(cont’d)
Shortest Path calculation

40. Routing Algorithms(cont’d)
Shortest Path calculation

41. Routing Algorithms(cont’d)
Shortest Path calculation

42. Routing Algorithms(cont’d)
Shortest Path calculation

43. Routing Algorithms(cont’d)
Shortest Path calculation

44. Routing Algorithms(cont’d)
Shortest Path calculation

45. Routing Algorithms(cont’d)
Shortest Path calculation

46. Routing Algorithms(cont’d)
Shortest Path calculation

47. Routing Algorithms(cont’d)
Shortest Path calculation

48. Routing Algorithms(cont’d)
Shortest Path calculation

49. Routing Algorithms(cont’d)
Shortest Path calculation

50. Routing Algorithms(cont’d)
Shortest Path calculation

51. Routing Algorithms(cont’d)
Shortest Path calculation

52. Routing Algorithms(cont’d)
Routing Table
~ In link state routing, the link state database is the same for all routers, but shortest path trees and the routing tables are different for each router.

53. Routing Algorithms(cont’d)
Link state routing table for router A

54. 16.6 요약