 
 HUT Comms Lab., Timo O. Korhonen
 
  
  
 
  
  
 
  
  
 
  
  
 
  
  
  
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
 
  
  
  
  
 Switching: 
 Transfer modes
 & connections
 Circuit switching
 Packet switching
 Connection oriented
 Connectionless
 
 - hand-shaking
 - strict error requirements
 - for fast data transfer
  
 
 - broadcasting
 - modest error rates
  
 often accepted
 - fast data in good channels
  
 Transfer modes
 Connection types
 - developed for data
 - nowadays also for voice
 - Statistical multiplexing
 - variable delays
  
 - developed for voice
 - nowadays also for data
 - well-specified delays
 - echo problems
  
 PSTN
 Ethernet
 X.25
 ATM
 Frame-relay
 UDP*
 *User
 Datagram Protocol