circuit       hard-state      soft-state      stateless
         switching     switching       switching       routing
    stateful|---------------+--------------+---------------|stateless
          POTS     |       ATM           MPLS          Internet
                   |                                   (packet
               C/S | P/S                                switching)
  • ISPs change part of backbone into MPLS
  • store and forward
  • when a packet arrived
    • store in a queue (waiting time)
    • waiting to be processed
    • queue for output port (waiting time)
    • transmitted (transmission time)
    • ~~~~ (propagation time)
  • how fast I can speak: transmission time

  • jitter: latency variation
  • throughput: how much you can transmit