ATM is connection oriented. At session initiation, call setup occurs in which the end stations and intervening switch set up a path and agree on link parameters such as peak data rate, burst size, etc.
Permanent Virtual Circuit. A type of ATM link between two end stations that is statically defined, usually by manual configuration. The PVC is the means by which QOS parameters are defined.
Synchronous Optical NETwork. A standard method of interconnecting data communications equipment at multiples of the OC-1 rate (typically 3, 12, 24, 48, 192).