Editing Frame Relay (section)

==Virtual circuits==
As a WAN protocol, Frame Relay is most commonly implemented at Layer 2 ([[data link layer]]) of the Open Systems Interconnection [[OSI model|(OSI) seven layer model]]. Two types of circuits exist: [[permanent virtual circuit]]s (PVCs) which are used to form logical end-to-end links mapped over a physical network, and [[switched virtual circuit]]s (SVCs). The latter are analogous to the circuit-switching concepts of the [[public switched telephone network]] (PSTN), the global phone network.