The call classification on Webex Calling determines whether a call is originating from an on-net source like on-premise PBX or from the PSTN, the concept is similar to Offnet and Onet Classification with Cisco Unified Communication Manager. Also, the call classification determines which destinations can be reached, this process is called screening, once the destination is allowed based on the source call, the call is routed out to the destination. This classification in the inbound call allows Webex Calling to avoid transit calls.
Based on Source Call Classification in the incoming calls, Webex Calling decides whether to route the call to the destination. The call classification at the inbound call based on the Caller ID prevents some transit Calls especially when using Cloud PSTN either Cloud Connect PSTN or Cisco Calling PSTN Plan.
