Which SIP request is used by a Cisco 9971 IP Phone to signal DND status changes to Cisco Unified Communications Manager?
Cisco Unified Communications Manager supports Do Not Disturb that a SIP device initiates or that a Cisco Unified Communications Manager device initiates.
A DND status change gets signaled from a SIP device to Cisco Unified Communications Manager by using the SIP PUBLISH method (RFC3909)
A DND status change gets signaled from a Cisco Unified Communications Manager to a SIP device by using a dndupdate Remote-cc REFER request.
Cisco Unified Communications Manager can also publish the Do Not Disturb status for a device, along with the busy and idle status for the device.
The correct answer is B. NOTIFY.
When a Cisco 9971 IP Phone changes its DND (Do Not Disturb) status, it uses the SIP NOTIFY request to signal this change to the Cisco Unified Communications Manager (CUCM). The NOTIFY request is part of the SIP (Session Initiation Protocol) messaging used in VoIP (Voice over IP) networks.
The NOTIFY request is a SIP event notification message that informs the recipient of a change in the state of a subscribed event. In this case, the Cisco 9971 IP Phone is subscribed to the DND status changes, and it sends a NOTIFY request to the CUCM when its DND status changes.
The CUCM then updates its database with the new DND status of the phone and notifies other devices that might be affected by the change. For example, if a call comes in for the phone while it is in DND mode, the CUCM can redirect the call to voicemail or another destination.
The other answer choices are as follows:
A. REGISTER: The REGISTER request is used by a SIP endpoint to register its address with a SIP server, such as the CUCM.
C. INFO: The INFO request is used to exchange information between SIP endpoints during a call, such as call hold or transfer.
D. PUBLISH: The PUBLISH request is used to publish information about the state of a SIP endpoint, such as its availability or location.
E. UPDATE: The UPDATE request is used to modify the state of a SIP session, such as changing the media properties or adding a third party to the call.
Therefore, the correct answer for the question is B. NOTIFY.