7
Transfer modes & connections summarized
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
ISDN
PCM
IP, Frame-relay
ATM
X.25
ATM
Frame-relay
IP, UDP*
*User Datagram Protocol