What is essential to enable single sign-on (SSO) to use Voice functionality?

To enable single sign-on (SSO) for Voice functionality, implementing a custom permission set is essential because it allows you to define the specific permissions and access levels required for users when they log in through the SSO mechanism. This ensures that users have the necessary authorization to utilize Voice features within the Service Cloud environment.

Custom permission sets can be tailored to include or restrict various functionalities relevant to Voice, enhancing security and user management. Therefore, establishing the right permission set is a critical step in the overall configuration for using Voice with SSO, as it ensures that the integration operates smoothly and aligns with the security protocols of the organization.

While other options may seem relevant, they do not directly address the specifics of SSO configuration for Voice functionality like the custom permission set does.