For call processing under the CUCM , you can find 2 types of traces :

  • System Diagnostic Interface (SDI) : SDI informations are traces from services and logs from run-time event.
  • System Diagnostic Layer (SDL) : SDL informations are traces from services as CUCM , CTI Manager and it stores logs state transitions between the node.

Most of the time , SDI traces will be the traces where you can find all stimuli and all interesting call processing traces regarding your phones. With a little knowledge ,it is not very difficult to read these traces

SDL traces are the transition states between the nodes and they are used more by Cisco TAC