Pass a token (in one direction) around a ring

Ring is logical, not necessarily physical link

• Every process $p_i$ has connection to process $p_{(i+1)\ mod\ N}$

Token arrival

• Only process in possession of token may access critical region
• Pass token on to neighbour if: no request upon arrival of token, or when exiting critical region

Algorithm satisfies ME1, ME2, but not ME3

Performance

• Bandwidth
  • Enter: 1 to N msg
  • Exit: 1 msg
• Client delay
  • 0 to N msg transmissions delays
• Synchronization delay
  • 1 to N-1 msg transmission delays