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Federated Authentication

Although many applications have their own system of accounts (including usernames and passwords), some applications rely on other services to verify the identity of users. This is called federated authentication.

In a corporate IT environment, applications may trust an Active Directory server, a LDAP server, or a SAML provider to authenticate users.

From

Cover of Getting Started with OAuth 2.0

Note

OpenID is emerging as an open standard for autheticaiton. It is based on OAuth.