RTP-NTE

SIP-NOTIFY

How do you send a digit:

You cannot see which digit was pressed. Only by using wireshark and decoding the binary digits.

SIP KPML

First advertise that you support it. Later on you can negotiate.

Now you know both sides support it. To be able to exchange digits, you have to subscribe to it.

If you receive a 200 OK to this subscription, you can send digits by sending notify: