Explanation/Reference:
Explanation:
Business-to-business calendar sharing is set up by creating organization relationships. User-to- user calendar sharing is set up by applying sharing policies.
There is no requirement for Contoso users to view the free/busy information of the A.Datum users.
Therefore, we don't need to create an organization relationship in A.Datum.
Configure Federated Sharing
Step 1: Create and configure a federation trust
(this has already been done here)
Step 2 (D): Create an organization relationship
An organization relationship enables users in your Exchange organization to share calendar free/busy information as part of federated sharing with other federated Exchange organizations.
Step 3 (E): Create a sharing policy
Sharing policies enable user-established, people-to-people sharing of both calendar and contact information with different types of external users. They support the sharing of calendar and contact information with external federated organizations, external non-federated organizations, and individuals with Internet access. If you don't need to configure people-to-people or contact sharing (organization-level sharing only), you don't need to configure a sharing policy.
Step 4: Configure an Autodiscover public DNS record
Note:
With federated sharing, users in your on-premises Exchange organization can share free/busy calendar information with recipients in other Exchange organizations that are also configured for federated sharing.
Free/busy sharing can be enabled between two organizations running Exchange 2013 and also between organizations with a mixed Exchange deployment.