Switching:
Transfer modes & connections
Transfer modes
Connection types
ATM
Circuit switching
PSTN
Connection oriented
- developed for voice
- nowadays also for data
- well-specified delays
- echo problems
Frame-relay
X.25
Packet switching
Connectionless
- developed for data
- nowadays also for voice
- Statistical multiplexing
- variable delays
- broadcasting
- modest error rates
  often accepted
- fast data in good channels
Ethernet
UDP*