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Broacast Routing
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Overview
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  • Unicast:
    • One sender and one receiver
  • Broadcast:
    • One sender and all receivers
  • Multicast:
    • One sender and a group of receivers
Uncontrolled Flooding
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  • Approach:
    • Source sends a copy of the packet to all of its neighbors
    • Each node does the same
  • Problems:
    • A cycle in the network causes the process to continue forever
    • When a node is connected to more than two others it will create and forward multiple copies causing a broadcast storm
Controlled Flooding
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  • Sequence Number Control:
    • The source includes its address and a sequence number in the packet
    • Each node keeps track of packets and doesn't re-broadcast
  • Reverse Path Forwarding (RPF):
    • The source includes its address
    • If the incoming link is on its shortest path back to the source then a node transmits the packet on all other links
Spanning Tree Broadcast
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  • Definitions:
    • A spanning tree is a tree that contains every node in the graph
    • A minimal spanning tree is a spanning tree that has minimum total link costs/weights
  • Broadcasting:
    • Each node knows the spanning tree
    • Each node broadcasts only to those links that are in the spanning tree
There's Always More to Learn
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