/mcpanother Unified Communications Manager node, Cisco Unified TSP sends a PHONE_STATE (PHONESTATE_RESUME) message to the TAPI application. The lines on the affected device also go out of service and in service, and Cisco Unified TSP sends LINE_LINEDEVSTATE (LINEDEVSTATE_OUTOFSERVICE) and LINE_LINEDEVSTATE (LINEDEVSTATE_INSERVICE) messages to the TAPI application. Call Survivability When a device or Unified Communications Manager failure occurs, no call survivability exists; however, media streams that are already connected between devices will survive. Calls in the process of being set up or modified (transfer, conference, redirect) simply get dropped. CTI Manager Failure When a primary CTI Manager fails, Cisco Unified TSP sends a PHONE_STATE (PHONESTATE_SUSPEND) message and a LINE_LINEDEVSTATE (LINEDEVSTATE_OUTOFSERVICE) message for every phone and line device that the application opened. Cisco Unified TSP then connects to a backup CTIManager. When a connection to a backup CTI Manager is established and the device or line successfully reopens, the Cisco Unified TSP sends a PHONE_STATE (PHONESTATE_RESUME) or LINE_LINEDEVSTATE (LINEDEVSTATE_INSERVICE) message to the TAPI application. If the Cisco Unified TSP is unsuccessful in opening the device or line for a CTI port or route point, the Cisco Unified TSP closes the device or line by sending the appropriate PHONE_CLOSE or LINE_CLOSE message to the TAPI application. After Cisco Unified TSP is connected to the backup CTIManager, Cisco Unified TSP will not reconnect to the primary CTIManager until the connection is lost between Cisco Unified TSP and the backup CTIManager. If devices are added to or removed from the user while the CTI Manager is down, Cisco Unified TSP generates PHONE_CREATE/LINE_CREATE or PHONE_REMOVE/LINE_REMOVE events, respectively, when connection to a backup CTI Manager is established. Support for Tertiary CTI Manager and Fallback This section is applicable from Release 15SU2 onwards. Important The secondary CTI Manager was referred to as the backup CTI Manager in earlier releases. Note Before this release, Cisco TSP enabled you to configure only a primary and secondary CTI Manager. From this release onwards, Cisco TSP enables you to configure a tertiary CTI Manager. When the tertiary CTI Manager is configured, it is treated as the least priority server. Cisco TSP connects to it only when connectivity to both the primary and secondary CTI Managers is lost. The TSP remains connected to tertiary by default unless you have explicitly enabled and configured a valid choice for fallback settings. For more information, see Fallback Settings, on page 113. Cisco Unified TAPI Application Failure When a Cisco TAPI application fails (the CTI Manager closes the provider), calls at CTI ports and route points that have not yet been terminated get redirected to the Call Forward On Failure (CFF) number that has been Cisco Unified TAPI Developers Guide for Cisco Unified Communications Manager, Release 15 and SUs 16 Overview Call Survivability