Algorithm mark all nodes tenta9ve set distances from

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Unformatted text preview: for a des9na9on is the union of all shortest paths G towards the des9na9on –  Similarly source tree F 2 4 E 3 10 3 2 4 A 4 B H 1 D 2 2 3 C 16 5 10/29/13 Sink Trees (2) F •  Implica9ons: –  Only need to use des9na9on 4 to follow shortest paths –  Each node only need to send G 3 to the next hop •  Forwarding table at a node A –  Lists next hop for each des9na9on –  Rou9ng table may know more 4 2 E 3 10 2 4 B 1 2 2 H D 3 C 17 Dijkstra’s Algorithm Algorithm: •  Mark all nodes tenta9ve, set distances from source to 0 (zero) for source, and ∞ (infinity) for all other nodes •  While tenta9ve nodes remain: –  Extract N, the one with lowest distance –  Add link to N to the shortest path tree –  Relax the distances of neighbors of N by lowering any beler distance es9mates 18 6 10/29/13 Dijkstra Comments •  Dynamic programming algorithm; leverages op9mality property •  Run9me depends on efficiency of extrac9ng min- cost node •  Gives us complete informa9on on the shortest paths to/from one node –  But requires complete topology 28 Introduc9on to Computer Networks Distance Vector Rou9ng (§5.2.4) Computer Science & Engineering 7 10/29/13 Topic •  How to compute shortest paths in a distributed network –  The Distance Vector (DV) approach Here’s my vector! Here’s mine 30 Distance Vector Rou9ng •  Simple, early rou9ng approach –  Used in ARPANET, and “RIP” •  One of two main approaches to rou9ng –  Distributed version of Bellman- Ford –  Works, but very slow convergence aier some failures •  Link- state algorithms are now typically used in prac9ce –  More involved, beler behavior 31 8 10/29/13 Distance Vector Se[ng Each node computes its forwarding table in a distributed se[ng: 1. ...
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This document was uploaded on 04/04/2014.

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