Chapter 14

1. Chapter 14 Unicast Routing Protocols:RIP, OSPF, and BGP Objectives Upon completion you will be able to: • Distinguish between intra and interdomain routing • Understand distance vector routing and RIP • Understand link state routing and OSPF • Understand path vector routing and BGP TCP/IP Protocol Suite

2. 14.1 INTRA- AND INTERDOMAIN ROUTING Routing inside an autonomous system is referred to as intradomain routing. Routing between autonomous systems is referred to as interdomain routing. TCP/IP Protocol Suite

3. Figure 14.1Autonomous systems TCP/IP Protocol Suite

4. Figure 14.2Popular routing protocols TCP/IP Protocol Suite

5. 14.2 DISTANCE VECTOR ROUTING In distance vector routing, the least cost route between any two nodes is the route with minimum distance. In this protocol each node maintains a vector (table) of minimum distances to every node The topics discussed in this section include: Initialization Sharing Updating When to Share Two-Node Loop Instability Three-Node Instability TCP/IP Protocol Suite

6. Figure 14.3Distance vector routing tables TCP/IP Protocol Suite

7. Figure 14.4Initialization of tables in distance vector routing TCP/IP Protocol Suite

8. Note: In distance vector routing, each node shares its routing table with its immediate neighbors periodically and when there is a change. TCP/IP Protocol Suite

9. Figure 14.5Updating in distance vector routing TCP/IP Protocol Suite

10. Figure 14.6Two-node instability TCP/IP Protocol Suite

11. Figure 14.7Three-node instability TCP/IP Protocol Suite

12. 14.3 RIP The Routing Information Protocol (RIP) is an intradomain routing protocol used inside an autonomous system. It is a very simple protocol based on distance vector routing. The topics discussed in this section include: RIP Message Format Requests and Responses Timers in RIP RIP Version 2 Encapsulation TCP/IP Protocol Suite

13. Figure 14.8Example of a domain using RIP TCP/IP Protocol Suite

14. Figure 14.9RIP message format TCP/IP Protocol Suite

15. Figure 14.10Request messages TCP/IP Protocol Suite

16. Example 1 Figure 14.11 shows the update message sent from router R1 to router R2 in Figure 14.8. The message is sent out of interface 130.10.0.2. The message is prepared with the combination of split horizon and poison reverse strategy in mind. Router R1 has obtained information about networks 195.2.4.0, 195.2.5.0, and 195.2.6.0 from router R2. When R1 sends an update message to R2, it replaces the actual value of the hop counts for these three networks with 16 (infinity) to prevent any confusion for R2. The figure also shows the table extracted from the message. Router R2 uses the source address of the IP datagram carrying the RIP message from R1 (130.10.02) as the next hop address. See Next Slide TCP/IP Protocol Suite

17. Figure 14.11Solution to Example 1 TCP/IP Protocol Suite

18. Figure 14.12RIP timers TCP/IP Protocol Suite

19. Example 2 A routing table has 20 entries. It does not receive information about five routes for 200 s. How many timers are running at this time? SolutionThe 21 timers are listed below:Periodic timer: 1 Expiration timer: 20 − 5 = 15 Garbage collection timer: 5 TCP/IP Protocol Suite

20. Figure 14.13RIP version 2 format TCP/IP Protocol Suite

21. Figure 14.14Authentication TCP/IP Protocol Suite

22. Note: RIP uses the services of UDP on well-known port 520. TCP/IP Protocol Suite

23. 14.4 LINK STATE ROUTING In link state routing, if each node in the domain has the entire topology of the domain, the node can use Dijkstra’s algorithm to build a routing table. The topics discussed in this section include: Building Routing Tables TCP/IP Protocol Suite

24. Figure 14.15Concept of link state routing TCP/IP Protocol Suite

25. Figure 14.16Link state knowledge TCP/IP Protocol Suite

26. Figure 14.17Dijkstra algorithm TCP/IP Protocol Suite

27. Figure 14.18Example of formation of shortest path tree TCP/IP Protocol Suite

28. Table 14.1 Routing table for node A TCP/IP Protocol Suite

29. 14.5 OSPF The Open Shortest Path First (OSPF) protocol is an intradomain routing protocol based on link state routing. Its domain is also an autonomous system. The topics discussed in this section include: Areas Metric Types of Links Graphical Representation OSPF Packets Link State Update Packet Other Packets Encapsulation TCP/IP Protocol Suite

30. Figure 14.19Areas in an autonomous system TCP/IP Protocol Suite

31. Figure 14.20Types of links TCP/IP Protocol Suite

32. Figure 14.21Point-to-point link TCP/IP Protocol Suite

33. Figure 14.22Transient link TCP/IP Protocol Suite

34. Figure 14.23Stub link TCP/IP Protocol Suite

35. Figure 14.24Example of an AS and its graphical representation in OSPF TCP/IP Protocol Suite

36. Figure 14.25Types of OSPF packets TCP/IP Protocol Suite

37. Figure 14.26OSPF common header TCP/IP Protocol Suite

38. Figure 14.27Link state update packet TCP/IP Protocol Suite

39. Figure 14.28LSA general header TCP/IP Protocol Suite

40. Figure 14.29Router link TCP/IP Protocol Suite

41. Figure 14.30Router link LSA TCP/IP Protocol Suite

42. Table 14.2 Link types, link identification, and link data TCP/IP Protocol Suite

43. Example 3 Give the router link LSA sent by router 10.24.7.9 in Figure 14.31. See Next Slide SolutionThis router has three links: two of type 1 (point-to-point) and one of type 3 (stub network). Figure 14.32 shows the router link LSA. See Figure 14.32 TCP/IP Protocol Suite

44. Figure 14.31Example 3 TCP/IP Protocol Suite

45. Figure 14.32Solution to Example 3 TCP/IP Protocol Suite

46. Figure 14.33Network link TCP/IP Protocol Suite

47. Figure 14.34Network link advertisement format TCP/IP Protocol Suite

48. Example 4 Give the network link LSA in Figure 14.35. See Next Slide Solution. See Figure 14.36 TCP/IP Protocol Suite

49. Figure 14.35Example 4 TCP/IP Protocol Suite

50. Figure 14.36Solution to Example 4 TCP/IP Protocol Suite