Wormhole Routing (cont)

• Helps avoid Deadlock

  • Deadlock - some subset of messages are mutually blocked waiting for a free buffer.
  • Figure 17.11
  • Deadlock formed by cycles in channel dependency graph - virtual channels can be used to cycles (Figure 17.12)

• Also helps to avoid LiveLock

  • Messages cycle endlessly without reaching destination
  • Happens in flow control policies in which new routes are chosen based on collisions or blockage

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