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Introduction to computer networking

Introduction to computer networking. Distributed Algorithms Class Recitation. Ex. 1 - PIF Revisited. Given the PIF algorithm: Init:  l N ( l )0; m 0; p 0 Upon receipt of MSG s ( l ) N ( l )1 if m =0 then p1 send MSG s to all l N -{ l } m 1

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Introduction to computer networking

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  1. Introduction to computer networking Distributed Algorithms Class Recitation

  2. Ex. 1 - PIF Revisited • Given the PIF algorithm: Init: l N(l)0; m0; p0 Upon receipt of MSGs(l) N(l)1 if m=0 then p1 send MSGsto all lN-{l} m1 if l’ holds N(l’)=1 then send MSGs to p m0 l’ N(l’)0 • Is it possible that a node i will send messages to all its neighbors except its parent, p, before node p has? • Is it possible for node i to send a message to its parent p before node j has finished sending messages to its neighbors?

  3. T=0

  4. T=3

  5. T=4

  6. T=5

  7. T=6

  8. T=7

  9. T=8

  10. T=11

  11. Ex. 2 • Given the PIFD algorithm, which is similar to the PIF algorithm, albeit with a second (other than the source) unique node D which behaves differently from the other nodes. For each of the following claims, determine whether the claim is true or false:

  12. The Claims • All the nodes will receive the message after a finite time period and all will have m=1 eventually. • The algorithm ends. i.e. there is a finite time after which no more messages are transferred. • The source node knows when the algorithm has finished • When the source node finishes the algorithm, the algorithm has ended.

  13. PIFD Algorithm For Node D: Init: Init: l N(l)0;m0; p0 Upon receipt of MSGs(l) N(l)1 if m=0 then p1 send MSGsto all neighbours m1

  14. The Claims Revisited • All the nodes will receive the message after a finite time period and all will have m=1 eventually. • The algorithm ends. i.e. there is a finite time after which no more messages are transferred. • The source node knows when the algorithm has finished • When the source node finishes the algorithm, the algorithm has ended.

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