414Lecture14

414Lecture14 - Lecture 14 Network Layer Distance Vector,...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 14 Network Layer Distance Vector, NATs, IPv6 ECSE 414 – Fall 2010
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ECSE 414, Lecture 14 2 Announcements Homework Assignment #3 due Tuesday, Oct 26 2010 Michael Rabbat
Background image of page 2
ECSE 414, Lecture 13 3 Dijkstra Review 7 2 2 4 5 3 6 2 3 4 2 2 F B C E D H A G “source” 2010 Michael Rabbat
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ECSE 414, Lecture 14 4 Dijkstra’s Algorithm Summary Each node knows the entire network graph and link costs Setup a table and compute the shortest paths from one node to all other nodes in the network Example: each router computes shortest paths from itself to all other IP addresses Given shortest paths, can form the routing table used to forward packets. Key properties: Greedy algorithm Centralized (need global knowledge) 2010 Michael Rabbat
Background image of page 4
ECSE 414, Lecture 14 5 u u u 0 (u) v 2 (v) w 5 (w) x 1 (x) y z 2 5 1 w v x Initially, u only knows which nodes it is directly connected to 2010 Michael Rabbat
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ECSE 414, Lecture 14 6 u u u 0 (u) v 2 (v) w x 1 (x) y z 2 5 1 w v x message from x u 1 v 2 w 3 x 0 y 1 z message from v u 2 v 0 w 3 x 2 y z message from w u 5 v 3 w 0 x 3 y 1 z 5 Bellman-Ford Equation: D u (dest) = min n=u,v,w,x {c(u,n) + D n (dest)} 4 (x) 2 (x) 10 (w) u receives messages from each neighbor with their distance vector, stores and uses this information 2010 Michael Rabbat
Background image of page 6
ECSE 414, Lecture 14 7 u u u 0 (u) v 2 (v) w x 1 (x) y 2 (x) z 2 5 1 w v x v u 2 v 0 w 3 x 2 y z w u 5 v 3 w 0 x 3 y 1 z 5 Bellman-Ford Equation: D u (dest) = min n=u,v,w,x {c(u,n) + D n (dest)} 3 (x) 4 (x) z new msg from x u 1 v 2 w 2 x 0 y 1 z 3 u receives messages from each neighbor with their distance vector, stores and uses this information 2010 Michael Rabbat
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ECSE 414, Lecture 14 8 Distance-Vector Routing Algorithm Bellman-Ford Equation (dynamic programming) Define d x (y) := cost of least-cost path from x to y Then d x (y) = min {c(x,v) + d v (y) } where min is taken over all neighbors v of x v Decentralized: Routers only know about immediate neighbors 2010 Michael Rabbat
Background image of page 8
ECSE 414, Lecture 14 9 Bellman-Ford example u y x w v z 2 2 1 3 1 1 2 5 3 5 Clearly, d v (z) = 5, d x (z) = 3, d w (z) = 3 d u (z) = min { c(u,v) + d v (z), c(u,x) + d x (z), c(u,w) + d w (z) } = min {2 + 5, 1 + 3, 5 + 3} = 4 Node that achieves minimum is next hop in shortest path forwarding table B-F equation says: 2010 Michael Rabbat
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ECSE 414, Lecture 14 10
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 26

414Lecture14 - Lecture 14 Network Layer Distance Vector,...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online