When a UC Administrator is troubleshooting DTMF negotiated by this SIP INVITE, which two messages should be examined next to further troubleshoot the issue?

Refer to the exhibit.

When a UC Administrator is troubleshooting DTMF negotiated by this SIP INVITE, which two messages should be examined next to further troubleshoot the issue? (Choose two.)
A . PRACK
B . UPDATE
C . SUBSCRIBE
D . NOTIFY
E . REGISTER

View Answer

Answer: CD