RFC 2833 to SIP KPML Negotiation
The Oracle® Enterprise Session Border Controller adds an Allow-Event header with the value KPML to the INVITE message.
If a SUBSCRIBE message is received from the Access side, the Oracle® Enterprise Session Border Controller will respond with a 200 OK message.
A KPML NOTIFY request is sent for each 2833 DTMF entered, until the subscription is terminated.