Different types of network services
Circuit switched services
Connect, communicate, disconnect
Fixed capacity reserved from the network for each connection
Based on Time Division Multiplexing (TDM)
E.g. the Public Switched Telecommunications Network (PSTN) and the Nordic Public Data Network (X.21 Datex)
Based on virtual connections which are set up and discon-nected but do not reserve fixed capacity from the network
Enable statistical multiplexing and more efficient use of network capacity
Connectionless (datagram) services
Each datagram is routed separately through the network
For example the Internet and most local area networks (LANs)