See Also 
Use the Terminate method to cancel connecting or Alerted sessions. In Session Initiation Protocol (SIP) messaging there is a distinction between an established or connected session; and a session that is connecting or alerted, in other words one that is not accepted yet by the remote endpoint.
- When terminating a connected session, a BYE is sent to the
remote endpoint.
- When canceling a connecting (or alerted, or outgoing) session,
a CANCEL request is sent to the remote endpoint that is then
acknowledged by a 200OK. The INVITE transaction then receives a 487
response from the remote endpoint.
Unified Communications Managed API version 1.0 exposes one method, the Terminate method, to terminate both types of sessions - established and not established. See the example in Terminating an Established Session.
