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Lecture 5: Unicast Routing Protocols - RIP

Understand the concepts and functioning of RIP, an intradomain routing protocol based on distance vector routing. Learn about RIP message format, timers, and authentication.

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Lecture 5: Unicast Routing Protocols - RIP

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  1. Lecture 5 Unicast Routing Protocols:RIP Objectives Upon completion you will be able to: • Distinguish between intra and interdomain routing • Understand distance vector routing and RIP Dr. Hussam Dheaa Kamel

  2. 5.1 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.

  3. Figure 5.1Autonomous systems

  4. Figure 5.2Popular routing protocols

  5. 5.2 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

  6. Figure 5.3Distance vector routing tables

  7. Figure 5.4Initialization of tables in distance vector routing

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

  9. Figure 5.5Updating in distance vector routing

  10. Figure 5.6Two-node instability

  11. Figure 5.7Three-node instability

  12. 5.3 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

  13. Figure 5.8Example of a domain using RIP

  14. Figure 5.9RIP message format

  15. Figure 5.10Request messages

  16. Example 1 Figure 5.11 shows the update message sent from router R1 to router R2 in Figure 5.8. 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

  17. Figure 5.11Solution to Example 1

  18. Figure 5.12RIP timers

  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

  20. Figure 5.13RIP version 2 format

  21. Figure 5.14Authentication

  22. Note: RIP uses the services of UDP on well-known port 520.

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