How do we send trac along them 68 20 102913 equal cost

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Unformatted text preview: S 53 Link- State Algorithm Proceeds in two phases: 1.  Nodes flood topology in the form of link state packets –  Each node learns full topology 2.  Each node computes its own forwarding table –  By running Dijkstra (or equivalent) CSE 461 University of Washington 55 15 10/29/13 Topology Dissemina9on •  Each node floods link state packet (LSP) that describes their por9on of the topology 4 Node E’s LSP flooded to A, B, C, D, and F Seq. # A 10 B 4 C 1 D 2 F 2 G F 2 E 3 10 3 2 4 A 4 B H D 1 2 2 3 C 56 Route Computa9on •  Each node has full topology –  By combining all LSPs •  Each node simply runs Dijkstra –  Some replicated computa9on, but finds required routes directly –  Compile forwarding table from sink/ source tree –  That’s it folks! 57 16 10/29/13 Handling Changes •  Nodes adjacent to failed link or node will no9ce –  Flood updated LSP with less connec9vity F F’s LSP B’s LSP Seq. # A 4 C 2 E 4 F 3 G 3 Seq. # B 3 E 2 G 4 Failure! 2 4 G XXXX 3 10 3 2 4 A 4 B H E D 1 2 2 3 C 59 Handling Changes (2) •  Link failure –  Both nodes no9ce, send updated LSPs –  Link is removed from topology •  Node failure –  All neighbors no9ce a link has failed –  Failed node can’t update its own LSP –  But it is OK: all links to node removed 60 17 10/29/13 Handling Changes (3) •  Addi9on of a link or node –  Add LSP of new node to topology –  Old LSPs are updated with new link •  Addi9ons are the easy case … 61 Link State Complica9ons •  What can go wrong? CSE 461 University of Washington 62 18 10/29/13 DV/LS Comparison •  How do the two compare? CSE 461 University of Washington 64 Introduc9on to Computer Networks Equal- Cost Mul9- Path Rou9ng (§5.2.1) Computer Scie...
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This document was uploaded on 04/04/2014.

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