In the past, digital switching networks were considered to be reliable and secure.
Since they used dedicated infrastructure they were very expensive relative to output, for example the international frame relay.
Network providers commonly implement frame relay for voice and data as an encapsulation technique, used between LANs over a WAN. Each end-user gets a private line (or leased line) to a frame-relay node. The frame-relay network handles the transmission over a frequently-changing path transparent to all end-users.