The controller sends a notification to the agent when the file updates are retrieved, and {HEAD ~ the agent} retrieves the file updates from {TAIL ~ the controller} 
The controller sends a notification to the agent when the file updates are retrieved , and { HEAD ~ the agent } retrieves the file updates from { TAIL ~ the controller }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL