An ITU-T TCAP primitive may be one of the following types:
Unidirectional : A single primitive with no subsequent primitives. Sometimes referred to as a Notice.
Begin: Start a dialog, further primitives will follow.
Continue: Send a subsequent primitive on an existing dialog, further primitives will follow.
End: The last primitive on an existing dialog, Close an existing dialog.
Abort: An error has caused the dialog to close.
Cancel: The invoke timer has expired without a response being received (this is a primitive but not a message)