Switching Techniques

• Circuit Switching
  • Circuit is established for the complete duration
  • based on TDM
  • Also referred to as STM (Synchronous Transfer Mode)
  • Very inflexible, since once the duration of time slot is determined, the relative bit rate is fixed
• Packet Switching
  • User information is encapsulated in packets
  • Packets contain additional information used inside the network for routing, error correction, flow control, etc
  • Designed in the sixties, when only poor to medium quality transmission links were available
  • Packets have variable length and hence require complex buffer management inside the network
• Frame relaying
  • Eliminates as much as possible of the overhead of packet switched networks
  • No hop-by-hop flow control and error control
  • Can be viewed as streamlined version of X.25