Which protocol allows for Single Sign-On (SSO) across multiple organizations?

A.  OAuth

B.  SAML

C.  RADIUS

D.  LDAP

Answer:  B

Explanation:

SAML (Security Assertion Markup Language): SAML is an XML-based standard for exchanging authentication and authorization data between parties. It is particularly useful for enabling Single Sign-On (SSO) across multiple organizations, known as federated SSO. This allows a user to log in once and gain access to resources across a range of different domains or organizations without being prompted to log in again.

Here's a breakdown of the other options:

OAuth: While OAuth is used for token-based authentication, it's generally used for authorizing third-party access to a user's data without exposing their password. It's not specifically designed for SSO across multiple organizations.

RADIUS (Remote Authentication Dial-In User Service): RADIUS is an older protocol used for remote user authentication and accounting. It's mostly used in VPNs and wireless authentication but is not designed for SSO across multiple organizations.

LDAP (Lightweight Directory Access Protocol): LDAP is used to access and maintain distributed directory information services over an IP network. It is commonly used for single sign-on within a single organization but isn't designed for SSO across multiple organizations.

Therefore, SAML is the protocol that allows for Single Sign-On (SSO) across multiple organizations.