WS-Federation (Web Services Federation) describes the management and brokering of trust relationships and security token exchange across Web services and organizational boundaries. WS-Federation is a part of the larger WS-Security framework. For example, WS-Federation builds on the Security Token Service (STS) by providing mechanisms that facilitate interactions. In the WS-Federation Model, an Identity Provider is a Security Token Service (STS).
See Configuring WS-Federation Single Sign-On via Identity Server to configure WS-Federation in WSO2 Identity Server