A SIP Trunk is a logical connection between an IP PBX and a Service Provider’s application servers that allows voice over IP traffic to be exchanged between the two. When a call is placed from an internal phone to an external number, the PBX sends the necessary information to the SIP Trunk provider who establishes the call to the dialed number and acts as an intermediary for the call. All signaling and voice traffic between the PBX and the provider is exchanged using SIP and RTP protocol packets over the IP network. Which two statements about SIP trunk are true?

A.
A SIP trunk configuration is mandatory for a UC500 device.

B.
A SIP trunk is needed for internet access

C.
A SIP trunk is needed only for voice if you are planning on using VoIP through a service provider.

D.
A SIP trunk is not supported in a keyswitch configuration.