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Lecture 16

Lecture 16. Routing: Intra-domain Protocols (interior gateway protocols (IGPs). Protocol layers across an internetwork. Routing versus Forwarding. Routing Table:. Forwarding Table:. Network as a graph. Goal: Find the lowest cost route between any two nodes. Nodes Edges Costs.

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Lecture 16

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  1. Lecture 16 Routing: Intra-domain Protocols (interior gateway protocols (IGPs)

  2. Protocol layers across an internetwork

  3. Routing versus Forwarding Routing Table: Forwarding Table:

  4. Network as a graph Goal: Find the lowest cost route between any two nodes • Nodes • Edges • Costs

  5. Why routing protocols? • Link failures • New nodes • Congestion • Two approaches: • Distance Vector-based on local information • Link State-based on global information

  6. Distance-vector routing

  7. Global View: Final distances to other network nodes Viewing node Distant Nodes

  8. Routing Table Evolution: Node A

  9. Final Routing Table: Node A

  10. Failure of link A-C: Viewed by A

  11. Final Routing Table: Link A-C Failure

  12. Counting to Infinity

  13. Router Information Protocol (RIP)

  14. Link State Routing • Each node establishes a list of directly connected neighbors and cost of each link • Floods that information in a LSP to all neighbors • Retransmits LSPs from other nodes- but does not echo to sender

  15. Propagation of LSPs

  16. LSP Information • ID of sending node • Link-state of sending node • Sequence number • Time to live

  17. Route Calculation • Each node has enough information to map the network • Dijkstra’s shorted path algorithm used to compute the routes

  18. Example: Link State Routing

  19. Routing Table Calculation

  20. Routing Table Calculation

  21. Routing Table Calculation

  22. OSPF • Authentication • Hierarchy-Domains and Areas • Load Balancing

  23. OSPF Header Format

  24. OSPF link-state advertisement

  25. Metrics

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