Lecture 5

# Algorithm mark all nodes tenta9ve set distances from

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

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 &amp; 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. ...
View Full Document

## This document was uploaded on 04/04/2014.

Ask a homework question - tutors are online