Exam Identity-and-Access-Management-Architect Topic 4 Question 154 Discussion

Delegated authentication is a feature that allows Salesforce to delegate the authentication process to an external web service. The web service needs to include the source IP address of the user as a method parameter, so that Salesforce can pass it along with the username and password. UC should whitelist all Salesforce IP ranges on their corporate firewall, so that the web service can accept requests from Salesforce.
The return type of the web service methodshould be a Boolean value, indicating whether the authentication was successful or not. The web service can be written using either SOAP or REST protocol, but this is not a consideration for UC while building the web service. Delegated authentication is not enabled for the system administrator profile, but it can be enabled for other profiles or permission sets. References: Certification - Identity and AccessManagement Architect - Trailhead, [Delegated Authentication Single Sign-On],
[Implementing Single Sign-On Across Multiple Organizations]