Smart API Manager includes a security token service (STS) based on IdentityServer3 to fulfill the role of the Authorization Server, as required by the OAuth 2.0 specification. See Overview of OAuth 2.0 for detailed information on all of the OAuth 2.0 roles.
IdentityServer employs OpenID Connect as its protocol for authentication.
Therefore, these three technologies are inter-related and depend on one another. The following two topics show you where to get more information on IdentityServer and OpenID Connect.