For a while, Frame Relay was used to interconnect LANs across wide area networks. However, X.25 and well as Frame Relay have been supplanted by the Internet Protocol (IP) at the network layer, and the Asynchronous Transfer Mode (ATM) and or versions of Multi-Protocol Label Switching (MPLS) at layer two.
What were X.25 and Frame relay used for 
Frame Relay was used to interconnect LANs across wide area networks. However, X.25 and well as Frame Relay have been supplanted