Service Invoke: The Service Invoke primitive is used to make a service REQUEST in either a request or response mediation flow. The service may be Request/Response or One-Way. Multiple instances of the Service Invoke primitive are permitted in a flow, allowing a SERIES of service invocations to be performed. 

Callout: The Callout receives the message and calls the requested service and operation. There is a Callout node for each CONNECTED target operation in the mediation flow.

1. If the CALL is successful, the Callout Response node in the response flow receives the response message.
2. If the call is unsuccessful, the Callout can be set to retry service invocations depending on the TYPE of fault received.

Service Invoke: The Service Invoke primitive is used to make a service request in either a request or response mediation flow. The service may be Request/Response or One-Way. Multiple instances of the Service Invoke primitive are permitted in a flow, allowing a series of service invocations to be performed. 

Callout: The Callout receives the message and calls the requested service and operation. There is a Callout node for each connected target operation in the mediation flow.