Which two SCCP call signaling messages are initiated by Cisco Unified Communications Manager to an IP phone? (Choose two.)
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A. B. C. D. E. F.CE.
Upon receiving an OpenReceiveChannelmessage, the IP phone selects the UDP port number it wants to use to receive RTP packets and reports this information to call manager.
With the SCCP protocol architecture, the majority of the H.323 processing power resides in an H.323 proxythe Cisco CallManager.
The end stations (IP phones) run the Skinny client, which consumes less processing overhead.
The client communicates with CallManager using connection-oriented (TCP/IP-based) communication to establish a call with another H.323-compliant end station.
Once Cisco CallManager has established the call, the two H.323 end stations use connectionless (UDP/IP-based) communication for audio transmissions.
The SCCP (Skinny Client Control Protocol) is a proprietary signaling protocol used by Cisco Unified Communications Manager (CUCM) to control and manage IP phones. There are several SCCP call signaling messages that can be initiated by CUCM to an IP phone. Let's take a closer look at the options provided:
A. SoftKeyEvent: This message is sent by an IP phone to CUCM when a soft key is pressed. This is not a message initiated by CUCM to an IP phone, so option A is incorrect.
B. CloseReceiveChannelAck: This message is sent by an IP phone to CUCM to acknowledge the receipt of a CloseReceiveChannel message. This is not a message initiated by CUCM to an IP phone, so option B is incorrect.
C. CallState: This message is initiated by CUCM to an IP phone to inform it of the current state of a call (e.g., ringing, connected, on hold). This is one of the correct answers.
D. KeypadButton: This message is sent by an IP phone to CUCM when a digit is dialed using the keypad. This is not a message initiated by CUCM to an IP phone, so option D is incorrect.
E. OpenReceiveChannel: This message is initiated by CUCM to an IP phone to establish a new RTP (Real-time Transport Protocol) stream for media transmission. This is one of the correct answers.
F. Offhook: This message is initiated by an IP phone to CUCM when the handset is lifted off the hook. This is not a message initiated by CUCM to an IP phone, so option F is incorrect.
Therefore, the two SCCP call signaling messages that are initiated by CUCM to an IP phone are CallState and OpenReceiveChannel.