Hybrid Calendar Service with Microsoft Exchange integration reference

Hybrid Calendar benefits

Currently, the Hybrid Calendar integration with Microsoft Exchange provides the following major features:

Provide users the ability to schedule a collaboration meeting with any calendar client connected to Microsoft Exchange. You don't need to install plug-ins or extensions. Type a keyword into the Location field (for example, @webex or @meet) or put a video address URI or meeting address into the meeting body.
Show a meetings list in users' Webex App applications—desktop, mobile, and hard endpoints.
Pop up a notification with a Join button, also known as One Button to Push (OBTP).
Update a user’s Webex App presence status when the user sets up automatic replies in Outlook (sometimes referred to as out-of-office status).

This article gives an overview of how the Expressway-based Calendar Connector integrates on-premises Microsoft Exchange with the Webex cloud.

For similar overviews of the other Hybrid Calendar Service integrations, see the following articles:

For the latest feature and deployment information, see https://www.cisco.com/go/hybrid-services-calendar.

Data handling

The Hybrid Calendar receives meeting details from the calendar system and uses them as follows:

checks the meeting location and body for URIs and URLs to join the meeting
the title of the invite as the meeting title
the start and end times to show the meeting slot on the meetings list in Webex App and on some devices
the invitees to populate the participant list in the meetings list
the invitees to send them the Join button, when it's time to join
the meeting invite body to populate the Webex meeting agenda

The service sends encrypted data to the Webex cloud (and stores the data in encrypted form) to provide the meetings list and Join button.

The service does not store or transmit unencrypted data. Sensitive data such as meeting description, meeting body, and email addresses of invitees is always encrypted when stored and transmitted.

The Hybrid Calendar service retains meeting data for a limited time. The stored data covers meetings from 7 days in the past through 31 days in the future.

For data encryption, the Hybrid Calendar uses the same Webex cloud encryption service that Webex App uses. As such, the cloud Key Management Server (KMS) provides key management. If you choose to deploy Hybrid Data Security, your own on-premises KMS provides the key management. (For more details, see the Webex App Security Paper.)

Authentication and authorization during deployment

Our Expressway-based connector integrates Webex with supported versions of Microsoft Exchange through an impersonation account. The application impersonation management role in Exchange enables applications to impersonate users in an organization to perform tasks for the user. You configure the application impersonation role in Exchange and use it in the calendar connector for the Exchange configuration on the Expressway-C interface.

The Exchange impersonation account is Microsoft's recommended method for this task. Expressway-C administrators don't need to know the password, because an Exchange administrator enters the value in the Expressway-C interface. The interface obscures the password, even if the Expressway-C administrator has root access to the Expressway-C box. The Expressway-C encrypts the password for storage using the same credential encryption mechanism as other passwords on the Expressway-C.

For more security, enable TLS to secure EWS connections on the wire as outlined in the Deployment Guide for Webex Hybrid Calendar Service.

Provisioning process

Ongoing operations

The Hybrid Calendar uses Exchange Web Services (EWS) to access Microsoft Exchange calendar events. EWS supports a broad range of mailbox operations. However, the Hybrid Calendar uses only a subset of commands for calendar use cases.

Table 1. Operations currently used by Hybrid Calendar Service
EWS operation	Usage
ConvertId	Simple connectivity check.
FindItem	Search for events in a user's calendar.
GetFolder	Retrieve details about a calendar folder.
GetItem	Retrieve details about events in a calendar folder.
GetStreamingEvents	Receive streaming notifications on calendar events.
GetUserOofSettings	Retrieve a user's out-of-office settings.
Subscribe	Subscribe for notifications on changes to a user's calendar.
SyncFolderItems	Detect changed meetings when not subscribed (missed, upgrades, and so on).
Unsubscribe	Unsubscribe from notifications on changes to a user's calendar.
UpdateItem	Update properties of calendar events (including join information and extended properties).
CreateItem	Create a new meeting request based on the input the user provides in the Webex client. The system creates new meetings for both organizers and users based on their availability.
GetUserAvailability	Displays the user availability and free/busy status for a specified time range.

The Hybrid Calendar also makes periodic calls to the Autodiscover service to locate user mailboxes.