Public switched data network
From Wikipedia, the free encyclopedia
PSDN is an acronym for public switched data network, a publicly-available network supporting packet-switched data, separate from the PSTN.
Originally this term referred only to PSS (Packet Switch Stream), an X.25-based packet-switched network, mostly used to provide leased-line connections between local area networks and to the Internet using permanent virtual circuits (PVCs) . Today the term may refer not only to Frame relay and ATM (both also providing permanent virtual circuits), but also IP, GPRS and other packet switching techniques.
Although superficially similar to the PSDN, ISDN, ADSL, SDSL and VDSL are not examples of it. ISDN utilizes the PSTN circuit switched network, and DSL are point-to-point circuit mode communication services overlaid on the PSTN local loop copper wires, usually utilized for access to a packet switched broadband IP network.
