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ELEN 602 Lecture 20

More on Routing RIP, OSPF, BGP. ELEN 602 Lecture 20. RIP Message Format. 0 8 16 31. Command Version. Zero. Address Family Identifier Zero.

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ELEN 602 Lecture 20

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  1. More on Routing RIP, OSPF, BGP ELEN 602 Lecture 20

  2. RIP Message Format 0 8 16 31 Command Version Zero Address Family Identifier Zero IP Address Zero Zero Metric . . .

  3. OSPF Areas To another AS R1 N1 N5 N2 R3 R6 N4 R7 R2 N6 R4 R5 N3 Area 0.0.0.0 Area 0.0.0.1 R8 Area 0.0.0.2 N7 R = router N = network Area 0.0.0.3

  4. Runs on top of IP, protocol number 89 Neighbors are discovered through hello messages Adjacencies are established and link-state databases synchronized. Propagate LSAs through exchanges between adjacent routers. Compute Routing tables. OSPF Summary

  5. OSPF Message Header 0 8 16 31 Version Type Packet Length Router ID Area ID Checksum Authentication Type Authentication Authentication

  6. OSPF Hello Packet 0 16 24 31 Network Mask Hello Interval Options Priority Dead Interval Designated Router Backup Designated Router Neighbor 1 . . . Neighbor n

  7. OSPF Database Description packet 0 16 24 29 31 M S Interface MTU Options Zero I M Database Description Sequence Number LSA Header

  8. LSA Header 0 16 24 31 Link State Age Options Link State Type Link State ID Advertising Router Link State Sequence Number Link State Checksum Length

  9. Internal and External BGP iBGP R2 R3 AS2 eBGP eBGP R1 R4 AS3 AS1

  10. Connects AS Domains Uses AS numbers for routing. BGP peers use TCP port number 179 for message exchanges Once the AS routing database established, only updates are sent between BGP peers iBGP peers need a consistent view of connectivity BGP peers exchange path-vectors of AS for routes Different types of messages: open, update, notification, keepalive. BGP Summary

  11. iBGP Mesh R R eBGP eBGP iBGP R R iBGP iBGP iBGP iBGP R R iBGP eBGP eBGP R R

  12. 0 8 16 24 31 Marker Length Type: OPEN Version My Autonomous System Hold Time BGP Identifier Optional parameters length Optional Parameters Figure 8.44

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