When configuring SSO identity sources, which of the following is NOT an available option?

In the context of configuring Single Sign-On (SSO) identity sources in VMware vSphere, the available options provide various means of authenticating users. Active Directory, RADIUS, and LDAP are all recognized identity sources that can be integrated into vSphere for authentication purposes.

Active Directory is widely used in enterprise environments and provides a comprehensive directory service that integrates well with many applications, including vSphere. RADIUS (Remote Authentication Dial-In User Service) is a protocol that enables centralized authentication for network access but can also be configured as an identity source for applications needing to authenticate users. LDAP (Lightweight Directory Access Protocol) is a protocol used to access and maintain distributed directory information services, which is compatible with vSphere for authentication as well.

On the other hand, Apple Open Directory, while it does serve as a directory service, is not typically included as an identity source for SSO in VMware vSphere environments. VMware primarily focuses on standards and protocols like Active Directory, RADIUS, and LDAP that are widely recognized in enterprise setups for managing identity services. Thus, Apple Open Directory is generally not supported as a configuration option in this context.