SCCP Call Signaling Messages
Question
Which two SCCP call signaling messages are sent by an IP phone to Cisco Unified Communications Manager? (Choose two.)
Answers
Explanations
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A. B. C. D. E. F.AB.
This message indicates which soft key was pressed.
Upon receipt of this message, CallManager invokes the action associated with the pressed soft key.
For example, if Hold was the pressed soft key, CallManager places the active call on user hold.
In some trace files you might see a soft key number without the corresponding description.
The following list defines each soft key number.
SCCP (Skinny Client Control Protocol) is a Cisco proprietary protocol used for communication between IP phones and Cisco Unified Communications Manager (CUCM). SCCP uses different types of messages to signal different events in the call setup process.
Out of the given options, the two SCCP call signaling messages sent by an IP phone to CUCM are:
A. SoftKeyEvent - This message is sent by the IP phone to CUCM to inform about the user's action on a softkey. Softkeys are programmable buttons on IP phones used for functions like Hold, Transfer, Conference, and more. When a user presses a softkey, the IP phone sends a SoftKeyEvent message to CUCM with information about the key pressed, which CUCM uses to initiate the corresponding action.
D. SelectSoftKeys - This message is sent by the IP phone to CUCM to inform about the softkeys available on the phone. When the IP phone registers with CUCM, it sends a SelectSoftKeys message to inform CUCM about the available softkeys and their functions. CUCM uses this information to populate the softkey templates for the phone.
The other options are not SCCP call signaling messages sent by an IP phone to CUCM:
B. OpenReceiveChannelAck - This message is sent by CUCM to the IP phone to acknowledge the receipt of an OpenReceiveChannel message sent by the IP phone to request a voice channel for audio transmission.
C. StartMediaTransmission - This message is sent by CUCM to the IP phone to initiate the audio transmission on the allocated voice channel.
E. CloseReceiveChannel - This message is sent by CUCM to the IP phone to inform about the closure of the voice channel.
F. StopTone - This message is sent by CUCM to the IP phone to stop a tone generated by the phone, such as a busy tone or a ringback tone.
Therefore, the correct answers are A. SoftKeyEvent and D. SelectSoftKeys.
